Broadcast area calculation device and program

Abstract

To calculate an area where digital terrestrial broadcasting can be received with high accuracy and at high speed.SOLUTION: A preprocessing unit 30 of a broadcast area calculation unit 17 of a broadcast area calculation device 1-1 calculates a maximum distance kyori2 considering the free space propagation loss for each target direction hoko of 360 degrees horizontally with respect to the transmission point. A maximum point setting unit 31 calculates a maximum distance kyori considering the antenna gain, calculates an electric field E for each profile point, and sets a maximum point max_pt where the electric field E is equal to or greater than a required electric field min_se toward the transmission point from a distant place. The broadcast area calculation unit 17 sets the maximum point max_pt to area vertex coordinates area_data[hoko].ido,keido.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a broadcast area calculation device and a program for calculating an area capable of receiving terrestrial digital broadcast.

Background Art

[0002] Conventionally, the electric field strength at a receiving point of terrestrial digital broadcast is calculated by synthesizing direct waves, reflected waves, and diffracted waves. The electrical constants at the reflection points vary depending on fields, farmlands, seas, etc., and the electric field strength of the reflected wave depends on the reflection coefficient based on the electrical constants at the reflection points. Therefore, the combined electric field of the direct wave and the reflected wave at the receiving point varies depending on the land use situation at the reflection point, and it is necessary to consider not only the distance and altitude between the transmitting and receiving points but also the land use situation at the reflection point.

[0003] Also, when there is an obstacle such as a high mountain or building between the reflection point and the receiving point, it is not necessary to consider the reflected wave. On the other hand, the diffracted wave at the obstacle is considered, and the combined wave of the direct wave and the diffracted wave becomes the electric field strength at the receiving point. When the altitude of the obstacle is higher than the altitude on the straight line connecting the transmitting point and the receiving point, it is out of sight and the direct wave does not reach the receiving point. Therefore, it is necessary to calculate the electric field strength at the receiving point only by the diffracted wave.

[0004] In addition, even in the case of calculating only the diffracted wave, it is necessary to regard the diffraction point as the transmitting point, find the direct wave and the reflected wave again, and calculate the electric field strength at the receiving point. This calculation needs to be performed for the number of times of diffraction occurrence.

[0005] From this, since the electric field strength at the receiving point varies depending on the situation of the propagation path from the transmitting point to the receiving point, when calculated considering the above conditions, the electric field strength may vary greatly even at adjacent receiving points.

[0006] In order to calculate such an electric field strength, the Millington method described in the Ministry of Posts and Telecommunications Notification No. 640 (Non-Patent Document 1) (see, for example, Non-Patent Document 2) is widely used. Also, a service area calculation method for medium-wave broadcasting using this method has been reported (see, for example, Non-Patent Document 3).

Prior Art Documents

Non-Patent Documents

[0007]

Non-Patent Document 1

Non-Patent Document 2

Non-Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0008] On the other hand, since actual radio wave propagation has the nature of waves, diffraction occurs and complex reflections are repeated by buildings, etc. during propagation. Therefore, in order to obtain an accurate received electric field, in addition to accurate terrain and building data, calculation of radio wave propagation considering the nature of waves is required, and there is a problem that the calculation time is very long.

[0009] Also, even when attempting to accurately determine the received electric field by such a procedure, there is a problem that the electric field value fluctuates with time due to fluctuations in the refractive index of the air.

[0010] Also, at locations where no one lives, such as in the sea area, there is no need to accurately determine the electric field value in the first place.

[0011] Therefore, the present invention has been made to solve the above problems, and an object thereof is to provide a broadcast area calculation device and a program capable of accurately and quickly calculating an area where terrestrial digital broadcasting can be received.

Means for Solving the Problems

[0012] In order to solve the above problems, the broadcast area calculation device according to claim 1 is a broadcast area calculation device that calculates a broadcast area where terrestrial digital broadcasting can be received. Based on the transmission point of the broadcast station, for each target direction hoko obtained by dividing 360 degrees horizontally at predetermined angles, a broadcast area calculation unit that calculates the latitude and longitude of the area vertex group of the broadcast area that satisfies a predetermined required electric field min_se as area vertex coordinates area_data[hoko].ido, keido. The broadcast area calculation unit includes a preprocessing unit that calculates the maximum distance kyori2 of the reception point by free space propagation based on the effective radiated power of the transmission point ERP, which is the effective radiated power of the radio wave transmitted from the antenna of the broadcast station, and the required electric field min_se. Using the reception point corresponding to the maximum distance kyori2 calculated by the preprocessing unit as a virtual reception point, calculates the electric field E for each profile point between the transmission point and the virtual reception point, and determines whether the electric field E is greater than or equal to the required electric field min_se for each profile point from the virtual reception point towards the transmission point. A maximum point setting unit that sets the first profile point determined to have the electric field E greater than or equal to the required electric field min_se as the maximum point max_pt, and is characterized by setting the maximum point max_pt to the area vertex coordinates area_data[hoko].ido, keido.

[0013] Also, the broadcast area calculation device according to claim 2 is the broadcast area calculation device according to claim 1, further comprising a farthest point setting unit that sets a farthest point. The farthest point setting unit calculates a maximum width max1 in which the electric field E is equal to or greater than the required electric field min_se from the transmission point toward the maximum point max_pt set by the maximum point setting unit, and sets the profile point closest to the maximum point max_pt at the point of the maximum width max1 as the farthest point max_p. From the transmission point toward the farthest point max_p, a maximum width max2 in which the electric field E is less than the required electric field min_se is calculated, and the profile point closest to the farthest point max_p at the point of the maximum width max2 is set as the farthest point min_p. It is determined whether the maximum width max2 is wider than a predetermined value. When it is determined that the maximum width max2 is not wider than the predetermined value, the coordinates of the farthest point max_p are set as the area vertex coordinates area_data[hoko].ido, keido. When it is determined that the maximum width max2 is wider than the predetermined value, from the transmission point toward the farthest point min_p, a maximum width max3 in which the electric field E is equal to or greater than the required electric field min_se is calculated, and the profile point closest to the farthest point min_p at the point of the maximum width max3 is reset as the farthest point max_p and set in the area vertex coordinates area_data[hoko].ido, keido. From the farthest point max_p toward the maximum point max_pt, the widths at which the electric field E is less than the required electric field min_se are sequentially calculated, and the maximum width among them is set as the maximum width dspan. When the width is larger than the set maximum width dspan, the maximum width dspan is updated, and a width A at which the electric field E is equal to or greater than the required electric field min_se is calculated. When the width A exceeds a predetermined multiple of the maximum width dspan, the profile point closest to the maximum point max_pt at the point of the width A is set as the area vertex coordinates area_data[hoko].ido, keido.

[0014] The broadcast area calculation device according to claim 3 is the broadcast area calculation device according to claim 1 or 2, further comprising a broadcast area correction unit that averages the positions of a predetermined number of adjacent area vertex coordinates area_data[hoko].ido, keido for each target direction hoko calculated by the broadcast area calculation unit.

[0015] The broadcast area calculation device according to claim 4 is the broadcast area calculation device according to any one of claims 1 to 3, wherein the maximum point setting unit calculates an average value based on the electric field E of a plurality of consecutive profile points including the profile point for each profile point from the transmission point to the maximum point max_pt, and sets the average value as the electric field E of the profile point.

[0016] The broadcast area calculation device according to claim 5 is the broadcast area calculation device according to any one of claims 1 to 4, wherein the maximum point setting unit calculates the antenna directivity ant_loss for each predetermined angle j in the vertical direction of the antenna of the broadcasting station, sets the antenna directivity ant_loss at which the gain of the antenna is maximum as the antenna directivity a_loss, calculates the maximum distance kyori based on the maximum distance kyori2 and the antenna directivity a_loss, uses the maximum distance kyori instead of the maximum distance kyori2, sets the reception point corresponding to the maximum distance kyori as the virtual reception point, and sets the maximum point max_pt.

[0017] The broadcast area calculation device according to claim 6 is the broadcast area calculation device according to claim 3, further comprising a land use data storage unit that stores land use data for each mesh of a predetermined size, and the broadcast area correction unit reads the land use data at the positions of the area vertex coordinates area_data[hoko].ido, keido from the land use data storage unit. When the land use data is a sea area, averaged the area vertex coordinates area_data[hoko].ido, keido are shown averaged the area vertex coordinates area_data[hoko].ido, keido indicate su eso that the rear vertex does not enter the mesh of the sea area averaged characterized in that the positions of the area vertex coordinates area_data[hoko].ido and keido are moved toward the transmission point side

[0018] Further, the broadcast area calculation device according to claim 7 is the broadcast area calculation device according to any one of claims 1 to 5, and further includes a land use data storage unit that stores land use data for each mesh of a predetermined size. The maximum point setting unit reads the land use data of the profile points between the transmission point and the virtual reception point from the land use data storage unit, determines whether the land use data of the profile points is a sea area, and calculates the electric field E for the profile points when the land use data is not the sea area.

[0019] Furthermore, the program according to claim 8 is based on the effective radiated power ERP of the transmission point of the radio wave transmitted from the antenna of the broadcast station and the required electric field min_se, for each target direction hoko obtained by dividing 360 degrees horizontally at predetermined angles, calculates the latitude and longitude of the area vertex group of the broadcast area that satisfies the predetermined required electric field min_se as the area vertex coordinates area_data[hoko].ido and keido, a preprocessing unit that calculates the maximum distance kyori2 of the reception point by free space propagation, and for each profile point between the transmission point and the virtual reception point with the reception point corresponding to the maximum distance kyori2 calculated by the preprocessing unit as the virtual reception point, calculates the electric field E, determines whether the electric field E is greater than or equal to the required electric field min_se for each profile point from the virtual reception point toward the transmission point, functions as a maximum point setting unit that sets the first profile point determined to have the electric field E greater than or equal to the required electric field min_se as the maximum point max_pt, and sets the maximum point max_pt to the area vertex coordinates area_data[hoko].ido and keido. [Effect of the Invention]

[0020] As described above, according to the present invention, an area capable of receiving terrestrial digital broadcasts can be calculated with high accuracy and at high speed.

Brief Description of the Drawings

[0021]

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Mode for Carrying Out the Invention

[0022] Hereinafter, the embodiments of the present invention will be described in detail with reference to the drawings. Hereinafter, the range where radio waves emitted from a terrestrial digital broadcasting transmission point reach a receiving point where terrestrial digital broadcasting can be received and the electric field strength (hereinafter referred to as "electric field") at the receiving point satisfies a predetermined condition based on a required electric field is referred to as a "broadcast area."

[0023] Example 1 First, a description will be given of a broadcast area calculation device of Example 1. The broadcast area calculation device of Example 1 is characterized in that it calculates the electric field E for each profile point by determining a virtual reception point taking into account free space propagation loss and antenna gain for each target direction of 360 degrees horizontally with the transmission point as a reference, sets a maximum point max_pt in processing from a distance toward the transmission point, sets the farthest points max_p, min_p in processing from the transmission point toward a distance, and calculates the broadcast area by processing to compare the electric field E and the required electric field min_se. According to Example 1, the broadcast area can be calculated accurately and quickly.

[0024] Fig. 1 is a block diagram showing an example of the configuration of a broadcast area calculation device of Example 1, and Fig. 2 is a flowchart showing an example of processing by the broadcast area calculation device. This broadcast area calculation device 1-1 includes a required electric field input unit 10, a constant memory unit 11, a transmission point information memory unit 12, a topographical height data memory unit 13, a land reflection coefficient memory unit 14, a land use data memory unit 15, a land reflection coefficient calculation unit 16, a broadcast area calculation unit 17, a broadcast area information memory unit 18, a broadcast area correction unit 19, and a broadcast area drawing unit 20.

[0025] The required electric field input unit 10 has a function of inputting two required electric fields syoyou_e and syoyou_e2 that serve as a reference for calculating the broadcast area according to the user's operation, and a function of inputting an instruction to start the process of calculating the broadcast area. The required electric field input unit 10 outputs the required electric fields syoyou_e and syoyou_e2 and the start instruction input according to the user's operation to the broadcast area calculation unit 17. Here, although the required electric field input unit 10 is configured to input two required electric fields syoyou_e and syoyou_e2, it is sufficient if one or more of the two required electric fields syoyou_e and syoyou_e2 can be input.

[0026] The constant storage unit 11 stores a constant of the number of steps in the angular direction hoko_step. The number of steps in the angular direction hoko_step indicates the unit of the angle when determining the direction in which the broadcast area is calculated in 360 degrees of one rotation with respect to the transmission point. For example, the number of steps in the angular direction hoko_step = 2 [degrees] is used. In this case, the broadcast area is calculated for each direction every 2 degrees with respect to 360 degrees. The number of steps in the angular direction hoko_step is preset by the user or stored by external means.

[0027] The transmission point information storage unit 12 stores transmission point information such as the latitude and longitude of the broadcast station to be calculated (hereinafter referred to as the "transmission point"), the antenna height (transmission point height send_h), the antenna gain, and the effective radiated power ERP of the transmission point. The transmission point information is preset by the user or stored by external means. The effective radiated power ERP of the transmission point is the effective power of the radio wave transmitted from the antenna of the broadcast station.

[0028] The terrain height data storage unit 13 stores the height of the terrain (terrain height data) in a mesh shape with a predetermined size (for example, 5 [m] square, 10 [m] square, 50 [m] square). The terrain height data for each mesh of the predetermined size is preset by the user or stored by external means.

[0029] The land reflectivity storage unit 14 stores the land reflectivity for each mesh of a predetermined size calculated by the land reflectivity calculation unit 16. The land reflectivity is used when calculating the reflected wave at the time of calculating the electric field E of the profile point in the calculation process of the broadcast area.

[0030] The land use data storage unit 15 stores land use data for each mesh of a predetermined size. The land use data is data classified into, for example, sea areas, terraced hills, and large undulating mountains.

[0031] The land reflectivity calculation unit 16 reads out the land use data for each mesh of a predetermined size from the land use data storage unit 15. Then, the land reflectivity calculation unit 16 calculates the land reflectivity based on the land use data and stores the land reflectivity for each mesh of a predetermined size in the land reflectivity storage unit 14.

[0032] For example, the land reflectivity calculation unit 16 has a table (a preset table) in which the relationship between the land use data and the land reflectivity is defined. The land reflectivity calculation unit 16 reads out the land use data from the land use data storage unit 15 for each mesh of a predetermined size, reads out the land reflectivity corresponding to the land use data from the table, and stores this in the land reflectivity storage unit 14.

[0033] The broadcast area calculation unit 17 inputs the required electric field syoyou_e, syoyou_e2, and a start instruction from the required electric field input unit 10. Also, the broadcast area calculation unit 17 reads out the number of angular direction steps hoko_step (=2) from the constant storage unit 11, the transmission point information from the transmission point information storage unit 12, and the terrain height data for each mesh of a predetermined size from the terrain height data storage unit 13. Also, the broadcast area calculation unit 17 reads out the land reflectivity for each mesh of a predetermined size from the land reflectivity storage unit 14.

[0034] When the broadcast area calculation unit 17 inputs a start instruction from the required electric field input unit 10 (step S201), it starts the broadcast area calculation process (step S202).

[0035] That is, the broadcast area calculation unit 17 calculates the electric field E in the horizontal 360-degree direction with reference to the transmission point by using the required electric fields syoyou_e, syoyou_e2, the number of angular direction steps hoko_step, the transmission point information, the terrain height data for each mesh of a predetermined size, the land reflection coefficient, etc., and calculates the broadcast area where the electric field E at the reception point satisfies the required electric field min_se.

[0036] The broadcast area is composed of a group of area vertices connecting the farthest points where the electric field E satisfies the required electric field min_se in each direction of 360 degrees horizontally with reference to the transmission point, and is represented by the area vertex coordinates area_data[hoko].ido, keido which are the latitudes and longitudes of the group of area vertices.

[0037] The broadcast area calculation unit 17 stores the area vertex coordinates area_data[hoko].ido, keido as broadcast area information in the broadcast area information storage unit 18.

[0038] In the broadcast area information storage unit 18, the latitudes and longitudes of the group of area vertices that define the broadcast area are stored as the area vertex coordinates area_data[hoko].ido, keido for each target direction hoko obtained by dividing the horizontal 360-degree direction with reference to the transmission point by the number of angular direction steps hoko_step.

[0039] The broadcast area correction unit 19 reads out the area vertex coordinates area_data[hoko].ido, keido which are the broadcast area information from the broadcast area information storage unit 18. Then, the broadcast area correction unit 19 performs corrections such as eliminating the protrusion and indentation of the area vertices so that the shape (the shape of the broadcast area) formed by connecting the area vertex coordinates area_data[hoko].ido, keido of the group of area vertices becomes smooth (step S203). For example, the broadcast area correction unit 19 compares a plurality of adjacent area vertex coordinates area_data[hoko].ido, keido, detects the positions of the protruding area vertex coordinates area_data[hoko].ido, keido, and averages them.

[0040] The broadcast area correction unit 19 outputs the corrected area vertex coordinates area_data[hoko].ido, keido to the broadcast area drawing unit 20. The corrected area vertex coordinates area_data[hoko].ido, keido are treated as a vertex group for drawing the broadcast area in the broadcast area drawing unit 20. Details of the processing of the broadcast area correction unit 19 will be described later.

[0041] The broadcast area drawing unit 20 inputs the corrected area vertex coordinates area_data[hoko].ido, keido from the broadcast area correction unit 19. Then, based on the corrected area vertex coordinates area_data[hoko].ido, keido, the broadcast area drawing unit 20 generates a display signal for drawing the broadcast area on the map and outputs the display signal to the display device 2 (step S204).

[0042] Note that the broadcast area drawing unit 20 may input a drawing color from the required electric field input unit 10, generate a display signal for drawing the broadcast area on the map in the drawing color, and output the display signal to the display device 2.

[0043] 〔Broadcast Area Calculation Unit 17〕 Next, the broadcast area calculation unit 17 shown in FIG. 1 will be described in detail. FIG. 3 is a block diagram showing a configuration example of the broadcast area calculation unit 17, and FIG. 4 is a flowchart showing a processing example (step S202) of the broadcast area calculation unit 17.

[0044] The broadcast area calculation unit 17 includes a preprocessing unit 30, a maximum point setting unit 31, and a farthest point setting unit 32.

[0045] The broadcast area calculation unit 17 receives the required electric field syoyou_e, syoyou_e2, and start instruction from the required electric field input unit 10, and starts the broadcast area calculation process at the timing when the start instruction is received. Then, the broadcast area calculation unit 17 inputs the number of angular direction steps hoko_step from the constant storage unit 11, inputs the transmission point information from the transmission point information storage unit 12, and reads out the terrain height data and land reflection coefficient for each mesh of a predetermined size from the terrain height data storage unit 13 and the land reflection coefficient storage unit 14 respectively when calculating the electric field E of the reception point (step S401).

[0046] As a preparation process before calculating the electric field E in all directions from 0 to 360 degrees with the transmission point as the reference, the preprocessing unit 30 performs preprocessing such as setting the required electric field min_se and setting the maximum distance kyori2 of the reception point by free space propagation (step S402). Details of the preprocessing by the preprocessing unit 30 will be described later.

[0047] The maximum point setting unit 31 performs a process of setting the target direction hoko and the like for which the broadcast area is to be calculated (step S403). Details of the target direction setting process and the like by the maximum point setting unit 31 will be described later. For each set target direction hoko, the processes of steps S404 and S405 described later are performed.

[0048] The maximum point setting unit 31 performs processes (processes 1a, 1b, 1c, 1d) such as setting the maximum point max_pt based on the comparison of the electric field E of the reception point and the required electric field min_se from the far side where the virtual reception point is set toward the transmission point (step S404). Details of the maximum point setting process from the far side toward the transmission point by the maximum point setting unit 31 will be described later.

[0049] The maximum point max_pt is the profile point closest to the virtual reception point among the reception points that satisfy the required electric field min_se considering the effects of diffraction waves and reflection waves.

[0050] The farthest point setting unit 32 sets the farthest points max_p and min_p based on the maximum widths max1, max2, etc. derived from the comparison of the electric field E of the receiving point and the required electric field min_se in the direction from the transmission point to the distant virtual receiving point, and calculates the area vertex coordinates area_data[hoko].ido and keido of the area, etc. (processes 2a, 2b, 2c, 2d) (step S405).

[0051] The farthest point max_p is the profile point closest to the virtual receiving point among the receiving points with the maximum width max1 where the electric field E is equal to or greater than the required electric field min_se on the straight line from the transmission point to the virtual receiving point. Also, the farthest point min_p is the profile point closest to the virtual receiving point among the receiving points with the maximum width max2 where the electric field E is less than the required electric field min_se on the straight line from the transmission point to the virtual receiving point.

[0052] The farthest point setting unit 32 determines whether the processing for all target directions hoko is completed (step S406). If the farthest point setting unit 32 determines in step S406 that the processing for all target directions hoko is not completed (step S406: N), it proceeds to step S403. As a result, a new target direction hoko is set, and the processing of steps S403 to S405 is performed.

[0053] On the other hand, if the farthest point setting unit 32 determines in step S406 that the processing for all target directions hoko is completed (step S406: Y), it stores the area vertex coordinates area_data[hoko].ido and keido of all target directions hoko in the broadcast area information storage unit 18 as broadcast area information (step S407). The details of the farthest point setting process from the transmission point towards the distant direction by the farthest point setting unit 32 will be described later.

[0054] (Preprocessing) Next, the preprocessing of step S402 by the preprocessing unit 30 shown in FIG. 4 will be described in detail. FIG. 5 is a flowchart showing an example of the preprocessing (step S402).

[0055] The preprocessing unit 30 sets the number of angular direction steps hoko_step (for example, 2 [degrees]) to be used in the subsequent processing by reading the number of angular direction steps hoko_step from the constant storage unit 11 (step S501).

[0056] The number of angular direction steps hoko_step is an angle for discretely selecting 360 degrees horizontally around the transmission point. Here, as the vertex of the broadcast area is farther from the transmission point, adjacent vertices will be farther apart due to a 1-degree angular difference horizontally. Therefore, the number of angular direction steps hoko_step should be as fine as possible, but the finer the number of angular direction steps hoko_step, the greater the number of calculations. Thus, as a practical result, for example, by setting the number of angular direction steps hoko_step = 2 [degrees], the broadcast area can be calculated with sufficient accuracy.

[0057] The preprocessing unit 30 reads the transmission point information from the transmission point information storage unit 12, and based on the effective radiated power ERP of the transmission point included in the transmission point information, sets the distance direction step number stp so that the smaller the effective radiated power ERP of the transmission point, the smaller the value, and the larger the effective radiated power ERP of the transmission point, the larger the value (step S502).

[0058] For example, when the effective radiated power ERP of the transmission point is less than 1 [W], the preprocessing unit 30 sets the distance direction step number stp = 2. When the effective radiated power ERP of the transmission point is 1 [W] or more and less than 10 [W], the preprocessing unit 30 sets the distance direction step number stp = 3. Also, when the effective radiated power ERP of the transmission point is 10 [W] or more and less than 100 [W], the preprocessing unit 30 sets the distance direction step number stp = 4. When the effective radiated power ERP of the transmission point is 100 [W] or more and less than 1000 [W], the preprocessing unit 30 sets the distance direction step number stp = 5. Also, when the effective radiated power ERP of the transmission point is 1000 [W] or more and less than 10000 [W], the preprocessing unit 30 sets the distance direction step number stp = 6. When the effective radiated power ERP of the transmission point is 10000 [W] or more, the preprocessing unit 30 sets the distance direction step number stp = 7.

[0059] As a result, the smaller the effective radiated power ERP of the transmission point, the smaller the distance-direction step number stp with a small value is set, and the larger the effective radiated power ERP of the transmission point, the larger the distance-direction step number stp with a large value is set. This distance-direction step number stp is used in Process 1d described later.

[0060] Here, when the effective radiated power ERP of the transmission point is large, the broadcast area will spread further, and the maximum point max_pt and the virtual reception point calculated in the middle will also be points further away. Specifically, in Process 1d described later, the larger the effective radiated power ERP of the transmission point, the larger the number of profile points to be processed. Therefore, the number of times of setting the electric field E = 0 for each profile point and averaging the electric field E increases, and the processing load becomes high.

[0061] Therefore, the number of processing times is changed according to the magnitude of the effective radiated power ERP of the transmission point. Specifically, when the effective radiated power ERP of the transmission point is large, the preprocessing unit 30 sets a large value for the distance-direction step number stp, so as to reduce the number of processing times of Process 1d described later. Therefore, when the effective radiated power ERP of the transmission point is large, the processing load of Process 1d described later can be reduced, and high speed can be realized.

[0062] The preprocessing unit 30 inputs two required electric fields syoyou_e and syoyou_e2 from the required electric field input unit 10, and sets the lower one of the required electric fields syoyou_e and syoyou_e2 as the required electric field min_se (Step S503). Note that the preprocessing unit 30 may directly input the required electric field min_se from the required electric field input unit 10.

[0063] The preprocessing unit 30 calculates the maximum distance kyori2, which is the farthest distance considering free space loss, using the following formula based on the effective radiated power ERP of the transmission point and the required electric field min_se (Step S504). [Equation 1] kyori2=(7√ERP / 10 (min_se-60) / 20 )×1000[m] ···(1)

[0064] When the maximum distance kyori2 calculated in step S504 exceeds 1000 [km], the preprocessing unit 30 clips kyori2 to 1000 [km].

[0065] (Target direction and other setting process) Next, the target direction and other setting process of step S403 by the maximum point setting unit 31 shown in FIG. 4 will be described in detail. FIG. 6 is a flowchart showing an example of the target direction and other setting process (step S403).

[0066] Based on the number of angle direction steps hoko_step (for example, 2 [degrees]) set by the preprocessing unit 30, the maximum point setting unit 31 sets the target direction hoko to be calculated for the broadcast area by the following formula (step S601). [Equation 2] hoko = hoko_step × k [degrees] ··· (2) Here, the parameter k = 0, 1, ···, 179.

[0067] FIG. 20 is a diagram for explaining an example of the target direction hoko setting process (step S601). As shown in FIG. 20, in the horizontal 360-degree direction with the transmission point as the reference, the target directions hoko = 0, 2, ···, 358 [degrees] corresponding to k = 0, 1, ···, 179 are set. Also, the coordinates of the virtual reception point are calculated in step S602 described later.

[0068] Returning to FIG. 6, the maximum point setting unit 31 sets the point corresponding to the maximum distance kyori2 in the target direction hoko with the transmission point as the reference as the virtual reception point. The maximum point setting unit 31 calculates the virtual reception point coordinates (latitude and longitude of the virtual reception point) based on the maximum distance kyori2, the target direction hoko, and the latitude and longitude of the transmission point included in the transmission point information (step S602). Thereby, the virtual reception point coordinates are calculated for each target direction hoko.

[0069] (Process 1: Maximum point setting process from a distance towards the transmission point) Next, the process 1 in step S404 by the maximum point setting unit 31 shown in FIG. 4: the maximum point setting process from a remote location to the transmission point will be described in detail. FIG. 7 is a flowchart showing an example of the process 1: the maximum point setting process from a remote location to the transmission point (step S404).

[0070] For the antenna of the transmission point, the maximum point setting unit 31 calculates the antenna directivity for each vertical angle by changing the vertical angle of the antenna. Then, the maximum point setting unit 31 identifies the maximum antenna directivity (identifies the antenna directivity at which the antenna gain is maximum (loss is minimum)), and calculates the maximum distance kyori based on the maximum antenna directivity (step S701, process 1a).

[0071] The maximum point setting unit 31 calculates the virtual reception point coordinates corresponding to the maximum distance kyori, and calculates the electric field E for each profile point, the number of profile points p_count, and the number of steps p_step (step S702, process 1b).

[0072] The maximum point setting unit 31 specifies the electric field E at the specified point for each step number p_step from the electric field E for each profile point from the remote virtual reception point to the transmission point. Then, the maximum point setting unit 31 sets the maximum point max_pt through the comparison process of the electric field E at the specified point and the required electric field min_se (step S703, process 1c).

[0073] For the electric field E between the transmission point and the maximum point max_pt, the maximum point setting unit 31 averages a predetermined number of consecutive profile points, and sets the electric field E between the profile points after the maximum point max_pt and the virtual reception point to 0 (step S704, process 1d).

[0074] (Process 1a) Next, the process 1a in step S701 shown in FIG. 7: the maximum distance kyori calculation process based on the antenna directivity will be described in detail. FIG. 8 is a flowchart showing an example of the process 1a, and FIG. 21 is a diagram for explaining the example of the process 1a.

[0075] As described above, Process 1a is a process of calculating the antenna directivity for each vertical angle at the antenna of the transmission point, identifying the antenna directivity that maximizes the antenna gain (minimizes the loss), and calculating the maximum distance kyori based on the maximum antenna directivity.

[0076] The maximum point setting unit 31 sets the height of the virtual reception point to be the same as the transmission point height send_h which is the height of the transmission point, and initializes the antenna directivity a_loss (sets the minimum value that can be taken as the antenna directivity a_loss) (Step S801).

[0077] The maximum point setting unit 31 sets the vertical angle j for the antenna of the transmission point (Step S802). The angle j = 0, 2, ···, 10, and the angle j is set in order each time shifting from Step S801 and Step S806 described later.

[0078] The maximum point setting unit 31 calculates the virtual reception point height recv_h for calculation using the following formula based on the transmission point height send_h, the maximum distance kyori2, and the angle j (Step S803). [Equation 3] recv_h = send_h - floor{kyori2 × tan(jπ / 180) × 10} ···(3) floor represents the floor function.

[0079] The maximum point setting unit 31 calculates the antenna directivity ant_loss(recv_h) based on the virtual reception point height recv_h for calculation (Step S804). Specifically, the antenna directivity ant_loss(recv_h) is calculated based on the information of the reception point such as the virtual reception point height recv_h for calculation, with the position (latitude and longitude) and the transmission point height send_h of the transmission point being known.

[0080] The maximum point setting unit 31 determines whether the antenna directivity a_loss is smaller than the antenna directivity ant_loss(recv_h) (a_loss < ant_loss(recv_h)). If a_loss < ant_loss(recv_h), it sets the antenna directivity ant_loss(recv_h) to the antenna directivity a_loss (step S805). That is, the maximum point setting unit 31 sets the maximum value of the antenna directivity ant_loss(recv_h) to the antenna directivity a_loss. Here, the maximum point setting unit 31 calculates the virtual reception point height recv_h for calculation and calculates the antenna directivity ant_loss based on the virtual reception point height recv_h for calculation. However, since there is data on the gain characteristics in the angular direction measured during the manufacturing stage of the antenna, the maximum point setting unit 31 does not necessarily need to calculate the virtual reception point height recv_h for calculation.

[0081] In the first process, the antenna directivity a_loss is initialized as a value with a large loss. Therefore, the maximum point setting unit 31 determines a_loss < ant_loss(recv_h) and sets the antenna directivity ant_loss(recv_h) to the antenna directivity a_loss.

[0082] The maximum point setting unit 31 determines whether the processing for all angles j has been completed (step S806). If the maximum point setting unit 31 determines in step S806 that the processing for all angles j has not been completed (step S806: N), it proceeds to step S802. Then, the maximum point setting unit 31 performs the processing of steps S802 to S805 for the next angle j.

[0083] If the maximum point setting unit 31 determines in step S806 that the processing for all angles j has been completed (step S806: Y), it calculates the maximum distance kyori using the following formula based on the maximum distance kyori2 and the antenna directivity a_loss (step S807). [Equation 4] kyori = kyori2 × 10 a_loss / 20 ···(4)

[0084] In this way, in Process 1a, the maximum point setting unit 31 calculates the antenna directivity ant_loss(recv_h) for each angle j in the vertical direction of the antenna at the transmission point, sets the maximum antenna directivity ant_loss(recv_h) as the antenna directivity a_loss, and calculates the maximum distance kyori based on the maximum distance kyori2 and the antenna directivity a_loss. Here, the maximum antenna directivity ant_loss(recv_h) means that the gain of the antenna is maximum (the loss is minimum), that is, the radio wave can be transmitted farther. Thereby, the maximum distance kyori considering the minimum loss due to the antenna directivity is obtained.

[0085] Generally, the antenna directivity ant_loss(recv_h) is maximum in the central axis direction of the antenna (horizontal direction (0-degree direction) with respect to the ground). However, depending on the installation environment of the transmission point, the transmitting antenna is not necessarily installed in the central axis direction of the antenna. For this reason, the gain of the antenna changes due to the deviation of the angle in the vertical direction.

[0086] Since the maximum distance kyori2 is based on the premise that the height of the transmission point (transmission point height send_h) is the same as the height of the virtual reception point, this is the distance when the gain of the antenna is maximum. In calculating the maximum distance kyori, the antenna directivity ant_loss(recv_h) is obtained by lowering the height of the virtual reception point, and for the antenna directivity ant_loss(recv_h) with respect to the height of the virtual reception point corresponding to the deviation of the angle in the vertical direction of the transmitting antenna, the minimum value of the loss is set as the antenna directivity a_loss.

[0087] (Process 1b) Next, the process 1b of step S702 shown in FIG. 7: the calculation process of the electric field E, the profile point number p_count, and the step number p_step for each profile point will be described in detail. FIG. 9 is a flowchart showing an example of Process 1b, and FIG. 22 is a diagram for explaining an example of Process 1b.

[0088] As described above, Process 1b is a process of calculating virtual reception point coordinates corresponding to the maximum distance kyori, and calculating the electric field E, the profile point count p_count, and the step count p_step for each profile point between the transmission point and the virtual reception point.

[0089] The maximum point setting unit 31 calculates virtual reception point coordinates based on the maximum distance kyori, the target direction hoko, and the latitude and longitude of the transmission point included in the transmission point information (step S901).

[0090] The maximum point setting unit 31 reads terrain height data for the virtual reception point coordinates (for each mesh of the mesh size to be used) from the terrain height data storage unit 13, and specifies the terrain height (mesh height) of the virtual reception point coordinates. Then, the maximum point setting unit 31 adds an increment set in advance to the mesh height (the height from the ground to the antenna installed at the house), and sets the addition result as the height of the virtual reception point (step S902).

[0091] The maximum point setting unit 31 calculates the electric field E for each profile point between the transmission point and the virtual reception point as shown in the lower figure of FIG. 22 by executing profile calculation (step S903).

[0092] Specifically, the maximum point setting unit 31 calculates the electric field E for each profile point between the transmission point and the virtual reception point based on the virtual reception point coordinates, the height of the virtual reception point, the transmission point information read from the transmission point information storage unit 12, the terrain height data of the transmission point, the reflection point, and the reception point read from the terrain height data storage unit 13, the land reflection coefficients of the transmission point, the reflection point, and the reception point read from the land reflection coefficient storage unit 14, and the like.

[0093] Note that since the method of profile calculation for calculating the electric field E is known, detailed description is omitted here.

[0094] The maximum point setting unit 31 calculates the profile point count p_count based on the mesh size to be used and the distance between the transmission point and the virtual reception point (maximum distance kyori) (step S904).

[0095] The maximum location setting unit 31 calculates the number of steps p_step by the following formula based on the profile score p_count (step S905). [Equation 5] p_step = floor(p_count / 10) ···(5)

[0096] In the above formula (5), the maximum location setting unit 31 divides the profile score p_count by 10. However, 10 is an example and any positive integer can be used.

[0097] For example, referring to the lower diagram of FIG. 22, when the profile score p_count = 1000 and the number of steps p_step = floor(1000 / 10) = 100 are obtained.

[0098] The maximum location setting unit 31 corrects the number of steps p_step calculated in step S905 according to the mesh size to be used (step S906).

[0099] Specifically, when the number of steps p_step is larger than the number corresponding to the mesh size to be used, the maximum location setting unit 31 sets the number corresponding to the mesh size to be used as the number of steps p_step. For example, when the mesh size to be used is 10 [m] square, if the number of steps p_step is larger than 300, 300 is set as the number of steps p_step. Also, when the mesh size to be used is 50 [m] square, if the number of steps p_step is larger than 60, 60 is set as the number of steps p_step.

[0100] In this way, the maximum location setting unit 31 calculates the virtual reception point coordinates corresponding to the maximum distance kyori in process 1b, calculates the electric field E for each profile point between the transmission point and the virtual reception point, the profile score p_count, and the number of steps p_step, and corrects the number of steps p_step.

[0101] Here, in the profile calculation, the number of profile points p_count varies according to the mesh size used. When the mesh size is small, the number of profile points p_count increases, and the number of steps p_step also increases.

[0102] Therefore, in step S906, the maximum point setting unit 31 corrects the number of steps p_step so that it does not become larger than necessary according to the mesh size used. As a result, since the number of steps p_step does not increase, the calculation does not become rough, and the calculation accuracy can be ensured.

[0103] Also, in the processes 1c and the like described later, instead of performing processing for each of the profile points p_count (for example, 1000 points), processing is performed at intervals of the number of steps p_step (100 points) among the profile points p_count. That is, 1000 times of processing can be reduced to 10 times of processing, and a processing load of about 1 / 100 and a processing speed of about 100 times can be realized. The number of steps p_step is used to reduce the processing load and speed up the processing.

[0104] (Process 1c) Next, the process 1c: maximum point max_pt setting process of step S703 shown in FIG. 7 will be described in detail. FIG. 10 is a flowchart showing an example of the process 1c, and FIG. 23 is a diagram for explaining an example of the process 1c.

[0105] As described above, the process 1c is a process of specifying the electric field E at the designated point for each number of steps p_step from the electric field E for each profile point from the remote virtual reception point toward the transmission point, and setting the maximum point max_pt through the comparison process of the electric field E at the designated point and the required electric field min_se.

[0106] The maximum location setting unit 31 sets designated locations for each profile point at intervals of the number of steps p_step from a virtual reception point far away toward the transmission point (step S1001). The designated locations are set from the virtual reception point toward the transmission point when starting process 1c and every time migrating from step S1003 described later.

[0107] The maximum location setting unit 31 identifies the electric field E at the designated location from the electric field E for each profile point (step S1002).

[0108] The maximum location setting unit 31 determines whether the electric field E at the designated location is equal to or greater than the required electric field min_se (step S1003). In step S1003, when the maximum location setting unit 31 determines that the electric field E at the designated location is not equal to or greater than the required electric field min_se (step S1003: N), it migrates to step S1001. Then, the maximum location setting unit 31 sets the next designated location at intervals of the number of steps p_step toward the transmission point, and performs the processes of steps S1001 and S1002.

[0109] On the other hand, in step S1003, when the maximum location setting unit 31 determines that the electric field E at the designated location is equal to or greater than the required electric field min_se (step S1003: Y), it identifies the first designated location where the electric field E becomes equal to or greater than the required electric field min_se from the virtual reception point toward the transmission point. Then, the maximum location setting unit 31 adds the number of steps p_step to the designated location (step S1004). Then, the maximum location setting unit 31 sets the profile point of the addition result as the maximum location max_pt (step S1005).

[0110] The reason for not setting the designated location where the electric field E is determined to be equal to or greater than the required electric field min_se as the maximum location max_pt is to consider the possibility that there is a profile point with an electric field E equal to or greater than the required electric field min_se between the designated location and the profile point obtained by adding the number of steps p_step to the designated location (the point returned toward the virtual reception point by the number of steps p_step).

[0111] For example, referring to the lower diagram of FIG. 23, assume a case where it is determined that the electric field E at a specified point of the profile point 500 is equal to or greater than the required electric field min_se = 60. In this case, at the maximum point max_pt, the profile point obtained by adding the number of steps p_step = 100 to the specified point of the profile point 500 (the specified point of the profile point 600) is set. This is because it is considered that there may be a profile point with an electric field E equal to or greater than the required electric field min_se between the specified point of the profile point 500 and the specified point of the profile point 600. Note that in FIG. 23, there is no profile point with an electric field equal to or greater than the required electric field min_se between the specified point of the profile point 500 and the specified point of the profile point 600.

[0112] Returning to FIG. 10, the maximum point setting unit 31 corrects the maximum point max_pt set in step S1005 according to the transmitting point effective radiated power ERP (step S1006). Thereby, the maximum point max_pt is set at a position that is equal to or greater than the distance preset according to the transmitting point effective radiated power ERP (the distance that the radio wave reaches).

[0113] Specifically, the maximum point setting unit 31 determines whether the distance corresponding to the maximum point max_pt set in step S1005 (the distance between the transmitting point and the maximum point max_pt) is shorter than the distance preset according to the transmitting point effective radiated power ERP (the maximum distance that the radio wave reaches). Then, when the maximum point setting unit 31 determines that the distance corresponding to the maximum point max_pt is shorter than the preset distance, the maximum point max_pt is corrected to the profile point corresponding to that distance.

[0114] For example, when the mesh size to be used is 10 [m] square and the transmitting point effective radiated power ERP is greater than 100 [W], when the maximum point max_pt set in step S1005 is 1000 or less, 1000 is set as the maximum point max_pt. This is because when the transmitting point effective radiated power ERP is greater than 100 [W], it is assumed that the radio wave reaches 10 [km] or more from the transmitting point, and 1000×10 = 10 [km] is taken as the distance corresponding to the maximum point max_pt.

[0115] Also, when the mesh size to be used is 10 [m] square and the effective radiated power ERP of the transmission point is 100 [W] or less, when the maximum point max_pt set in step S1005 is 300 or less, 300 is set as the maximum point max_pt. This is because when the effective radiated power ERP of the transmission point is 100 [W] or less, it is assumed that radio waves can reach 3 [km] or more from the transmission point, and 300 × 10 = 3 [km] is taken as the distance corresponding to the maximum point max_pt.

[0116] For example, when the mesh size to be used is 50 [m] square and the effective radiated power ERP of the transmission point is greater than 100 [W], when the maximum point max_pt set in step S1005 is 200 or less, 200 is set as the maximum point max_pt. This is because when the effective radiated power ERP of the transmission point is greater than 100 [W], it is assumed that radio waves can reach 10 [km] or more from the transmission point, and 200 × 50 = 10 [km] is taken as the distance corresponding to the maximum point max_pt.

[0117] Also, when the mesh size to be used is 50 [m] square and the effective radiated power ERP of the transmission point is 100 [W] or less, when the maximum point max_pt set in step S1005 is 60 or less, 60 is set as the maximum point max_pt. This is because when the effective radiated power ERP of the transmission point is 100 [W] or less, it is assumed that radio waves can reach 3 [km] or more from the transmission point, and 60 × 50 = 3 [km] is taken as the distance corresponding to the maximum point max_pt.

[0118] In this way, the maximum point setting unit 31, in process 1c, identifies the electric field E at the specified point for each step number p_step from the electric field E at each profile point from the virtual reception point toward the transmission point, sets the maximum point max_pt through the comparison process of the electric field E at the specified point and the required electric field min_se, and corrects the maximum point max_pt according to the effective radiated power ERP of the transmission point.

[0119] If Process 1c is a process from the transmission point to the virtual reception point, the electric field E between the transmission point and the maximum point max_pt to be set varies due to terrain undulations and the like, and there are many profile points where the electric field E is equal to or greater than the required electric field min_se. Therefore, the processing load for setting the maximum point max_pt is high and it takes a long time.

[0120] On the other hand, by setting Process 1c as a process from the virtual reception point to the transmission point, it is only necessary to obtain the profile point that is first determined to have an electric field E equal to or greater than the required electric field min_se. Therefore, the processing load can be reduced and high-speed processing can be achieved. In particular, when the effective radiated power ERP of the transmission point is large, the virtual reception point will be located farther away, so the reduction of the processing load and the acceleration of the processing can be further realized.

[0121] In addition, since the processing for each step number p_step is performed, the number of processes can be reduced compared to the processing for each profile point, and the reduction of the processing load and the acceleration of the processing can be realized.

[0122] Still, the maximum point setting unit 31 obtains the step number p_step by dividing the number of profile points p_count by, for example, 10 which is a positive integer (the above formula (5)), sets the specified point for each profile point at intervals of the step number p_step from the virtual reception point to the transmission point, and when the electric field E at the specified point is equal to or greater than the required electric field min_se, adds the step number p_step to the specified point and sets the profile point indicated by the addition result as the maximum point max_pt.

[0123] On the other hand, the maximum point setting unit 31 may determine whether the electric field E of the profile point is equal to or greater than the required electric field min_se from the virtual reception point to the transmission point, and set the profile point that is first determined to have an electric field E equal to or greater than the required electric field min_se as the maximum point max_pt.

[0124] (Process 1d) Next, the process 1d in step S704 shown in FIG. 7: the electric field averaging process and the like will be described in detail. FIG. 11 is a flowchart showing an example of the process 1d, and FIG. 24 is a diagram for explaining an example of the process 1d.

[0125] As described above, the process 1d is a process of averaging a continuous predetermined number of profile points for the electric field E between the transmission point and the maximum point max_pt, and setting the electric field E between the profile points from after the maximum point max_pt to the virtual reception point to 0.

[0126] The maximum point setting unit 31 proceeds to step S1102 for the profile points between the transmission point and the maximum point max_pt, and proceeds to step S1105 for the profile points between the profile points from after the maximum point max_pt to the virtual reception point (step S1101).

[0127] The maximum point setting unit 31 changes the electric field E of the profile points between the transmission point and the maximum point max_pt so as to be constant (stepwise) at intervals of the distance direction step number stp (step S1102).

[0128] The maximum point setting unit 31 proceeds from step S1102 and calculates the average value of the electric field E of three consecutive profile points (the profile point and its before and after) for each profile point (step S1103). Then, the maximum point setting unit 31 sets the average value to the electric field E of the middle profile point among the three profile points (step S1104).

[0129] Thereby, a smooth electric field E as a whole can be obtained from the constant electric field E at the profile points at intervals of the distance direction step number stp.

[0130] On the other hand, the maximum point setting unit 31 sets the electric field E = 0 for each profile point for the profile points between the profile points from after the maximum point max_pt to the virtual reception point (step S1105).

[0131] In this way, in process 1d, the maximum point setting unit 31 averages the electric field E between the transmission point and the maximum point max_pt for a predetermined number of consecutive profile points, and sets the electric field E between the profile points after the maximum point max_pt and the virtual reception point to 0.

[0132] As a result, for the electric field E between the transmission point and the maximum point max_pt, it is averaged by the electric fields E of three consecutive profile points, so that fluctuations in the electric field E due to slight undulations of the terrain at short distances can be suppressed. In particular, fluctuations in the electric field E around the required electric field min_se can be suppressed, and in the comparison process of the electric field E and the required electric field min_se in process 2a and the like described later, the calculation amount can be suppressed, and reduction of the processing load and speeding up of the processing can be realized.

[0133] Also, since the electric field E between the profile points after the maximum point max_pt and the virtual reception point is set to 0, in process 2a and the like described later, the profile points in this range can be excluded from the processing targets, and reduction of the processing load and speeding up of the processing can be realized.

[0134] (Farthest point setting process from the transmission point towards the far end) Next, the process 2 of step S405 by the farthest point setting unit 32 shown in FIG. 4: The farthest point setting process from the transmission point towards the far end will be described in detail. FIG. 12 is a flowchart showing an example (step S405) of the process 2: The farthest point setting process from the transmission point towards the far end.

[0135] The farthest point setting unit 32 calculates the maximum width max1 at which the electric field E is equal to or greater than the required electric field min_se from the transmission point towards the maximum point max_pt at the far end, and sets the farthest point max_p (step S1201, process 2a).

[0136] The farthest point setting unit 32 calculates the maximum width max2 at which the electric field E is less than the required electric field min_se from the transmission point towards the farthest point max_p at the far end, and sets the farthest point min_p (step S1202, process 2b).

[0137] When the maximum width max2 at the time of setting the farthest point min_p is wider than a predetermined value, the farthest point setting unit 32 re - sets the farthest point max_p between the transmission point and the farthest point min_p by the same process as in step S1201 (step S1203, process 2c).

[0138] The farthest point setting unit 32 determines whether the farthest point max_p is closer to the transmission point than the farthest point min_p, and sets the area vertex coordinates area_data[hoko].ido, keido that define the broadcast area (step S1204, process 2d).

[0139] Incidentally, the farthest point setting unit 32 may set the coordinates of the maximum point max_pt set in process 1c of step S703 in FIG. 7 as the area vertex coordinates area_data[hoko].ido, keido. Also, the farthest point setting unit 32 may set the coordinates of the farthest point max_p set in process 2a of step S1201 as the area vertex coordinates area_data[hoko].ido, keido.

[0140] (Process 2a) Next, the process 2a of step S1201 shown in FIG. 12: the process of setting the farthest point max_p with an electric field of at least the required electric field min_se will be described in detail. FIG. 13 is a flowchart showing an example of process 2a, and FIG. 25 is a diagram for explaining an example of process 2a.

[0141] As described above, process 2a is a process of calculating the maximum width max1 at which the electric field E is at least the required electric field min_se from the transmission point toward the maximum point max_pt in the far - away direction, and setting the farthest point max_p.

[0142] The farthest point setting unit 32 calculates the width at which the electric field E is at least the required electric field min_se from the transmission point toward the maximum point max_pt, specifies the widest width, and sets the maximum width max1 (step S1301).

[0143] For example, in the lower diagram of FIG. 25, from the transmission point towards the maximum point max_pt, first, the width EW1 where the electric field E becomes equal to or greater than the required electric field min_se is calculated, and the maximum width max1 = EW1 is set. Thereafter, the width EW2 where the electric field E becomes equal to or greater than the required electric field min_se is calculated. Since EW1 > EW2, the maximum width max1 = EW1 is maintained. Then, the width EW3 where the electric field E becomes equal to or greater than the required electric field min_se is calculated. Since EW1 < EW3, the maximum width max1 = EW3 is set. Then, the process proceeds towards the maximum point max_pt, but since the width where the electric field E becomes equal to or greater than the required electric field min_se is not calculated, the maximum width max1 = EW3 is determined.

[0144] Returning to FIG. 13, the farthest point setting unit 32 sets, as the farthest point max_p, the profile point among the profile points included in the point of the maximum width max1 that is closest to the maximum point max_pt (the farthest from the transmission point) (step S1302).

[0145] For example, in the lower diagram of FIG. 25, among the profile points 350 to 530 included in the point of the maximum width max1 = EW3, the profile point 530 closest to the maximum point max_pt is set as the farthest point max_p.

[0146] In this way, the farthest point setting unit 32, in process 2a, targets the profile points between the transmission point and the maximum point max_pt far away from the transmission point, calculates the maximum width max1, and sets the farthest point max_p.

[0147] As a result, among the profile points between the transmission point and the virtual reception point, the profile points between the maximum point max_pt and the virtual reception point are excluded from the processing target, so that the processing load can be reduced and the processing speed can be increased.

[0148] (Process 2b) Next, the process 2b in step S1202 shown in FIG. 12: the process of setting the farthest point min_p less than the required electric field min_se will be described in detail. FIG. 14 is a flowchart showing an example of process 2b, and FIG. 26 is a diagram for explaining an example of process 2b.

[0149] As described above, process 2b is a process of calculating the maximum width max2 at which the electric field E is less than the required electric field min_se toward the farthest point max_p far from the transmission point, and setting the farthest point min_p.

[0150] The farthest point setting unit 32 calculates the width at which the electric field E is less than the required electric field min_se toward the farthest point max_p from the transmission point, specifies the widest width, and sets the maximum width max2 (step S1401).

[0151] For example, in the lower diagram of FIG. 26, toward the farthest point max_p from the transmission point, first, the width EW1 at which the electric field E becomes less than the required electric field min_se is calculated, and the maximum width max2 = EW1 is set. Thereafter, the width EW2 at which the electric field E becomes less than the required electric field min_se is calculated. Since EW1 < EW2, the maximum width max2 = EW2 is set. Then, the process is performed toward the farthest point max_p, but since the width at which the electric field E becomes less than the required electric field min_se is not calculated, the maximum width max2 = EW2 is determined.

[0152] Returning to FIG. 14, the farthest point setting unit 32 sets, as the farthest point min_p, the profile point closest to the farthest point max_p (the farthest from the transmission point) among the profile points included in the point of the maximum width max2 (step S1402).

[0153] For example, in the lower diagram of FIG. 26, among the profile points 300 to 350 included in the point of the maximum width max2 = EW2, the profile point 350 closest to the farthest point max_p is set as the farthest point min_p.

[0154] In this way, the farthest point setting unit 32 targets the profile points between the transmission point and the farthest point max_p far from the transmission point in process 2b, calculates the maximum width max2, and sets the farthest point min_p.

[0155] As a result, among the profile points from the transmission point to the virtual reception point, the profile points from the farthest point max_p to the virtual reception point are excluded from the processing target, so that the processing load can be reduced and the processing speed can be increased.

[0156] (Process 2c) Next, the process 2c: farthest point max_p reset process in step S1203 shown in FIG. 12 will be described in detail. FIG. 15 is a flowchart showing an example of process 2c, and FIG. 27 is a diagram for explaining an example of process 2c.

[0157] As described above, when the maximum width max2 at the time of setting the farthest point min_p is wider than a predetermined value, process 2c is a process of resetting the farthest point max_p by the same process as step S1201 of process 2a.

[0158] The farthest point setting unit 32 determines whether the maximum width max2 calculated in step S1401 of process 2b shown in FIG. 14 is wider than a predetermined value (for example, 10 [km]) (step S1501).

[0159] In step S1501, when the farthest point setting unit 32 determines that the maximum width max2 is wider than the predetermined value (step S1501: Y), it determines that it is inappropriate that the farthest point max_p is set farther than the farthest point min_p.

[0160] Assuming that it is inappropriate that the farthest point max_p is set farther than the farthest point min_p means that when the maximum width max2 is wider than the predetermined value, although there is a maximum width max2 which is a section where radio waves do not reach between the transmission point and the farthest point max_p, it is not reasonable that there is a farthest point max_p where radio waves reach beyond the section of the maximum width max2. Therefore, the farthest point max_p should be reset.

[0161] Therefore, the farthest point setting unit 32 calculates the width in which the electric field E is equal to or greater than the required electric field min_se from the transmission point toward the farthest point min_p, specifies the widest width, and sets the maximum width max3 (step S1502).

[0162] For example, in the lower diagram of FIG. 27, the width EW1 in which the electric field E is equal to or greater than the required electric field min_se is first calculated from the transmission point toward the farthest point min_p, and the maximum width max3 = EW1 is set. Thereafter, the width EW2 in which the electric field E is equal to or greater than the required electric field min_se is calculated. Since EW1 > EW2, the maximum width max3 = EW1 is maintained. Then, the process is performed toward the farthest point min_p, but since the width in which the electric field E is equal to or greater than the required electric field min_se is not calculated, the maximum width max3 = EW1 is determined.

[0163] Returning to FIG. 15, the farthest point setting unit 32 re-sets the profile point closest to the farthest point min_p (the farthest from the transmission point) among the profile points included in the point of the maximum width max3 as the farthest point max_p (step S1503).

[0164] For example, in the lower diagram of FIG. 27, among the profile points 0 to 180 included in the point where the maximum width max3 = EW1, the profile point 180 closest to the farthest point min_p is re-set as the farthest point max_p.

[0165] Returning to FIG. 15, on the other hand, when the farthest point setting unit 32 determines in step S1501 that the maximum width max2 is not wider than the predetermined value (step S1501: N), the process ends.

[0166] In this way, when the maximum width max2 at the time of setting the farthest point min_p is wider than the predetermined value in process 2c, the farthest point setting unit 32 targets the profile points between the transmission point and the farthest point min_p far from the transmission point, calculates the maximum width max3, and re-sets the farthest point max_p.

[0167] Accordingly, when the maximum width max2 is wider than a predetermined value, an appropriate farthest point max_p can be obtained instead of an inappropriate farthest point max_p. Also, when resetting the farthest point max_p, among the profile points between the transmission point and the virtual reception point, the profile points between the farthest point min_p and the virtual reception point are excluded from the processing target, so that the processing load can be reduced and the processing speed can be increased.

[0168] (Process 2d) Next, the process 2d in step S1204 shown in FIG. 12: the area vertex coordinate area_data[hoko].ido, keido setting process will be described in detail. FIG. 16 is a flowchart showing an example of process 2d, and FIG. 28 is a diagram for explaining an example of process 2d.

[0169] As described above, process 2d is a process of determining whether the farthest point max_p is closer to the transmission point than the farthest point min_p and setting the area vertex coordinates area_data[hoko].ido, keido.

[0170] The farthest point setting unit 32 determines whether the farthest point max_p is closer to the transmission point than the farthest point min_p (the farthest point max_p < the farthest point min_p) (step S1601). If the farthest point setting unit 32 determines in step S1601 that the farthest point max_p is closer to the transmission point than the farthest point min_p (step S1601: Y, the farthest point max_p < the farthest point min_p), it proceeds to step S1602. On the other hand, if the farthest point setting unit 32 determines in step S1601 that the farthest point max_p is not closer to the transmission point than the farthest point min_p (step S1601: N, the farthest point max_p ≧ the farthest point min_p), it proceeds to step S1609.

[0171] When it is determined that the farthest point max_p is closer to the transmission point than the farthest point min_p, in process 2c shown in FIG. 15, it is determined that the maximum width max2 is wider than a predetermined value, which corresponds to the case where the farthest point max_p is reset. On the other hand, when it is determined that the farthest point max_p is not closer to the transmission point than the farthest point min_p, in process 2c shown in FIG. 15, it is determined that the maximum width max2 is not wider than a predetermined value, which corresponds to the case where the farthest point max_p is not reset.

[0172] The farthest point setting unit 32 shifts from step S1601(Y), sets the farthest point max_p to the parameter upt (step S1602), and sets profile points from the point of the parameter upt toward the maximum point max_pt (step S1603). The profile points are set in order from the point of the parameter upt toward the maximum point max_pt each time the process shifts from step S1602 or step S1608 described later.

[0173] The farthest point setting unit 32 calculates the width at which the electric field E is less than the required electric field min_se from the point of the parameter upt toward the maximum point max_pt, sets it as the maximum width dspan, and updates the point of the parameter upt (step S1604). For the update of the point of the parameter upt, refer to step S1805 in FIG. 18 described later. Here, when a width wider than the initially set maximum width dspan is subsequently calculated from the point of the parameter upt toward the maximum point max_pt, the width is set as the new maximum width dspan.

[0174] The farthest point setting unit 32 calculates the first width A at which the electric field E is greater than or equal to the required electric field min_se from the point of the parameter upt toward the maximum point max_pt (step S1605).

[0175] The farthest point setting unit 32 multiplies the maximum width dspan by, for example, 1.5, and determines whether the width A is wider than the multiplication result (step S1606). If, in step S1606, the farthest point setting unit 32 determines that the width A is wider than the multiplication result (step S1606: Y), it calculates the coordinates of the profile point (latitude and longitude of the profile point closest to the maximum point max_pt at the location of the width A), and sets the coordinates as the area vertex coordinates area_data[hoko].ido,keido (step S1607). The coordinates of the profile point are calculated based on the position of the profile point between the farthest point max_p and the virtual reception point, the target direction hoko, and the latitude and longitude of the transmission point included in the transmission information.

[0176] Incidentally, after the area vertex coordinates area_data[hoko].ido,keido are set in the same target direction hoko, the process proceeds from step S1608 to step S1603, which will be described later. A new profile point may be set, and the new area vertex coordinates area_data[hoko].ido,keido may be reset in step S1607.

[0177] Also, if the maximum width dspan is not set in step S1604, if there is no width A at which the electric field E is equal to or greater than the required electric field min_se in step S1605, or if the conditions are not met in step S1606, the area vertex coordinates area_data[hoko].ido,keido are not set in step S1607. In this case, the farthest point setting unit 32 sets the coordinates of the farthest point max_p reset in step S1503 of FIG. 15 as the area vertex coordinates area_data[hoko].ido,keido.

[0178] On the other hand, if, in step S1606, the farthest point setting unit 32 determines that the width A is not wider than the multiplication result (step S1606: N), it proceeds to step S1608.

[0179] The farthest point setting unit 32 shifts from step S1607 or step S1606(N) and determines whether the processing of all profile points has been completed (step S1608). If the farthest point setting unit 32 determines in step S1608 that the processing of all profile points has not been completed (step S1608:N), it shifts to step S1603. Then, the farthest point setting unit 32 performs the processing of steps S1603 to S1607.

[0180] If the farthest point setting unit 32 determines in step S1608 that the processing of all profile points has been completed (step S1608:Y), it ends the processing.

[0181] For example, in the lower diagram of FIG. 28, from the point of parameter upt to the maximum point max_pt, when it is the profile point 200 for the first time, the width B1 at which the electric field E becomes less than the required electric field min_se is calculated, and the maximum width dspan = B1 is set. Then, when it is the profile point 300, the width A1 at which the electric field E becomes greater than or equal to the required electric field min_se is calculated. At this time, since the maximum width dspan = B1 and A1 > dspan × 1.5, the coordinates of the profile point 300 are set in the area vertex coordinates area_data[hoko].ido, keido.

[0182] When it is the profile point 350, the width B2 at which the electric field E becomes less than the required electric field min_se is calculated. Since B1 < B2, the maximum width dspan = B2 is set. Then, the processing is performed toward the maximum point max_pt, but since the width at which the electric field E becomes less than the required electric field min_se is not calculated, the maximum width dspan = B2 is maintained.

[0183] When at the profile point 530, the width A2 at which the electric field E becomes equal to or greater than the required electric field min_se is calculated. At this time, the maximum width dspan = B2, and since A2 > dspan × 1.5, the coordinates of the profile point 530 are reset to the area vertex coordinates area_data[hoko].ido, keido. Then, the process proceeds toward the maximum point max_pt. However, since the width at which the electric field E becomes equal to or greater than the required electric field min_se is not calculated, the coordinates of the profile point 530 are determined as the area vertex coordinates area_data[hoko].ido, keido.

[0184] Returning to FIG. 16, on the other hand, the farthest point setting unit 32 shifts from step S1601(N), calculates the coordinates of the farthest point max_p, sets the coordinates as the area vertex coordinates area_data[hoko].ido, keido (step S1609), and ends the process.

[0185] In this way, when the farthest point max_p is closer to the transmission point than the farthest point min_p in process 2d (when the farthest point max_p is reset by process 2c), the farthest point setting unit 32 calculates the maximum width dspan at which the electric field E becomes less than the required electric field min_se and the width A at which the electric field E becomes equal to or greater than the required electric field min_se from the farthest point max_p toward the maximum point max_pt, and sets the profile point where the width A exceeds 1.5 times the maximum width dspan and is closest to the maximum point max_pt as the area vertex coordinates area_data[hoko].ido, keido. Also, when the farthest point max_p is not closer to the transmission point than the farthest point min_p, the farthest point setting unit 32 sets the farthest point max_p as the area vertex coordinates area_data[hoko].ido, keido.

[0186] Accordingly, when the farthest point max_p is closer to the transmission point than the farthest point min_p, among the profile points from the farthest point max_p to the maximum point max_pt, the profile points from the farthest point max_p to the maximum point max_pt are the ones to be processed, and the profile points from the maximum point max_pt to the virtual reception point are not to be processed. Therefore, it is possible to reduce the processing load and speed up the processing.

[0187] Also, when the width A where the electric field E is equal to or greater than the required electric field min_se exceeds 1.5 times the maximum width dspan, the farthest point in the width A is set as the area vertex coordinates area_data[hoko].ido,keido. For this reason, the range such as the building shadow where the electric field E is less than the required electric field min_se and that exists between the transmission point and the width A (the maximum widths B1, B2 shown in the lower figure of FIG. 28) will be ignored when setting the area vertex coordinates area_data[hoko].ido,keido.

[0188] Note that the farthest point setting unit 32 uses 1.5 as the value for multiplying the maximum width dspan by a predetermined multiple in step S1606. However, the value of 1.5 is an example, and other values may be used. The numerical value multiplied by the maximum width dspan is preset by the user.

[0189] As a result of intensive studies by the inventors, the value of 1.5 was obtained as a suitable value for excluding building shadows and the like from the broadcast area. By using the value of 1.5, the user can accurately determine the validity of the broadcast area calculated by the broadcast area calculation device 1-1.

[0190] (Details of Process 2d) Next, steps S1602 to S1608 of process 2d shown in FIG. 16 will be described in detail. FIG. 17 is a flowchart showing details (1) of steps S1602 to S1608 of process 2d.

[0191] As described above, steps S1602 to S1608 of process 2d are processes when it is determined that the farthest point max_p is closer to the transmission point than the farthest point min_p.

[0192] First, the farthest point setting unit 32 sets the farthest point max_p to the parameter upt, the profile point count p_count to the parameter dpt, and 1 to the maximum width dspan (step S1701).

[0193] The farthest point setting unit 32 shifts from step S1701 and detects a profile point (i) where the electric field E is less than the required electric field min_se between the profile point of the point of the parameter upt (the farthest point max_p) and the profile point of the point of the profile point count p_count (the virtual reception point) (step S1702). Also, in step S1702, the farthest point setting unit 32 shifts from β in FIG. 17 (step S1809 in FIG. 18 described later) and detects the next profile point i.

[0194] Here, since the electric field E = 0 from the maximum point max_pt to the virtual reception point is set in step S1105 of FIG. 11, substantially, similar to step S1603 of FIG. 16, the process can be the process between the point of the parameter upt and the maximum point max_pt.

[0195] The farthest point setting unit 32 shifts to step S1704 assuming that the electric field E of the profile point i is less than the required electric field min_se or i ≧ p_count (step S1703).

[0196] The farthest point setting unit 32 determines whether the parameter upt = 1 or subtracts the distance of the point of the parameter upt (the distance between the transmission point and the point of the parameter upt) from the distance of the profile point i (the distance between the transmission point and the profile point i), and determines whether the subtraction result is greater than the result of multiplying the maximum width dspan by 1.5 (step S1704).

[0197] When the farthest point setting unit 32 determines in step S1704 that the condition is satisfied, that is, when it is determined that the parameter upt = 1, or when it is determined that the subtraction result of the distance from the distance of the point of the parameter upt from the distance of the profile point i is greater than the result of multiplying the maximum width dspan by 1.5 (step S1704: Y), it calculates the coordinates of the profile point (i - 1), sets the coordinates as the area vertex coordinates area_data[hoko].ido, keido (step S1705), and proceeds to step S1706.

[0198] On the other hand, when the farthest point setting unit 32 determines in step S1704 that the condition is not satisfied (step S1704: N), it proceeds to step S1706.

[0199] The farthest point setting unit 32 proceeds from step S1705 or step S1704 (N), sets i to the parameter dpt (step S1706), exits the loop (step S1707), and proceeds to α in FIG. 17 (step S1801 in FIG. 18 described later).

[0200] FIG. 18 is a flowchart showing the details (2) of steps S1602 to S1608 of process 2d, and shows the continuation of FIG. 17.

[0201] The farthest point setting unit 32 checks whether there is a profile point with a required electric field of min_se or more within the determination distance hantei_kyori. Here, the farthest point setting unit 32 sets the flag flag = False and i = 1 (step S1801).

[0202] Note that as the determination distance hantei_kyori, for example, the result of dividing the maximum distance kyori calculated by the maximum point setting unit 31 in step S807 of FIG. 8 by 5 is used.

[0203] That is, the farthest point setting unit 32 subtracts the distance of the profile point dpt (the distance from the transmission point to the profile point dpt) from the distance of the profile point (dpt+i) (the distance from the transmission point to the profile point (dpt+i)).

[0204] When the subtraction result is smaller than the determination distance hantei_kyori and (dpt+i)≤p_count, the farthest point setting unit 32 determines whether this is the case (step S1802).

[0205] If in step S1802, the farthest point setting unit 32 determines that the subtraction result is smaller than the determination distance hantei_kyori and (dpt+i)≤p_count (step S1802: Y), it proceeds to step S1803.

[0206] On the other hand, if in step S1802, the farthest point setting unit 32 determines that the subtraction result is not smaller than the determination distance hantei_kyori or (dpt+i)≤p_count is not satisfied (step S1802: N), it proceeds to step S1809.

[0207] After proceeding from step S1802 (Y), the farthest point setting unit 32 determines whether the electric field E of the profile point (dpt+i) is equal to or greater than the required electric field min_se (step S1803).

[0208] If in step S1803, the farthest point setting unit 32 determines that the electric field E of the profile point (dpt+i) is equal to or greater than the required electric field min_se (step S1803: Y), it sets the flag flag=True, sets (dpt+i) to the parameter upt (step S1805), and proceeds to step S1806.

[0209] On the other hand, when the farthest point setting unit 32 determines in step S1803 that the electric field E of the profile point (dpt+i) is less than the required electric field min_se (step S1803:N), it sets i=i+1 (step S1804) and proceeds to step S1802.

[0210] The farthest point setting unit 32 proceeds from step S1805, subtracts the distance of the profile point dpt from the distance of the profile point (dpt+i), and determines whether the maximum width dspan is smaller than the subtraction result (step S1806).

[0211] When the farthest point setting unit 32 determines in step S1806 that the maximum width dspan is smaller than the subtraction result (step S1806:Y), it sets the subtraction result to the maximum width dspan (step S1807) and proceeds to step S1808.

[0212] On the other hand, when the farthest point setting unit 32 determines in step S1806 that the maximum width dspan is not smaller than the subtraction result (step S1806:N), it proceeds to step S1808.

[0213] The farthest point setting unit 32 proceeds from step S1807 or step S1806(N), exits the loop (step S1808), and proceeds to step S1809.

[0214] The farthest point setting unit 32 proceeds from step S1802(N) or step S1808, and determines whether the flag flag=False or the parameter upt is greater than the number of profile points p_count (step S1809).

[0215] When the farthest point setting unit 32 determines in step S1809 that the flag flag is not False and the parameter upt is not greater than the number of profile points p_count (step S1809:N), it proceeds to β in FIG. 18 (step S1702 in FIG. 17).

[0216] On the other hand, when the farthest point setting unit 32 determines in step S1809 that the flag flag = False, or when it determines that the parameter upt is greater than the profile score p_count (step S1809: Y), it ends the process.

[0217] 〔Broadcast Area Correction Unit 19〕 Next, the broadcast area correction unit 19 shown in FIG. 1 will be described in detail. FIG. 19 is a flowchart showing a processing example (step S203) of the broadcast area correction unit 19.

[0218] The broadcast area correction unit 19 reads the broadcast area information from the broadcast area information storage unit 18 (step S1901). As described above, the broadcast area information is the area vertex coordinates area_data[hoko].ido, keido that define the broadcast area. The area vertex coordinates area_data[hoko].ido, keido are composed of the latitude and longitude of the area vertex for each target direction hoko obtained by dividing the 360-degree horizontal direction with respect to the transmission point into angular direction step numbers hoko_step.

[0219] The broadcast area correction unit 19 calculates the distances (distances of each area vertex) from the transmission point to the positions of each area vertex indicated by the area vertex coordinates area_data[hoko].ido, keido. Then, based on the distances of each area vertex, the broadcast area correction unit 19 averages the positions of each area vertex in the following steps S1902 to S1904.

[0220] For the area vertex in the target direction hoko, the broadcast area correction unit 19 determines whether the area vertex protrudes from other area vertices and whether it is indented, based on the distance of the area vertex and the distances of a predetermined number of other adjacent area vertices.

[0221] When the broadcast area correction unit 19 determines that the vertex of the area protrudes with respect to the vertices of other areas, it sets the new area vertex coordinates area_data[direction].latitude, longitude of the area vertex so as to eliminate the protrusion of the area vertex (step S1902).

[0222] Also, when the broadcast area correction unit 19 determines that the vertex of the area cuts into other area vertices, it sets the new area vertex coordinates area_data[direction].latitude, longitude of the area vertex so as to eliminate the cut of the area vertex (step S1903).

[0223] On the other hand, when the broadcast area correction unit 19 determines that the vertex of the area does not protrude with respect to the vertices of other areas and does not cut out, it maintains the area vertex coordinates area_data[direction].latitude, longitude of the area vertex.

[0224] After the processing of steps S1902 and S1903 is completed, the broadcast area correction unit 19 calculates the average value of the distances of a predetermined number of adjacent area vertices including the area vertex for the area vertex in the target direction direction. Then, the broadcast area correction unit 19 corrects the new area vertex coordinates area_data[direction].latitude, longitude of the area vertex to the latitude and longitude corresponding to the average value (step S1904).

[0225] The broadcast area correction unit 19 outputs the corrected new area vertex coordinates area_data[direction].latitude, longitude to the broadcast area drawing unit 20 as broadcast area information (step S1905).

[0226] In this way, the broadcast area correction unit 19 corrects each area vertex indicated by the area vertex coordinates area_data[direction].latitude, longitude by averaging based on the positions of a predetermined number of adjacent area vertices.

[0227] As a result, the unevenness of each area vertex with respect to the transmission point is alleviated, and a smooth curve broadcast area can be obtained. For example, when there is a building near the area vertex, the area vertex may cut into a predetermined number of other adjacent area vertices. Since radio waves can go around the building and reach farther, it is unnatural for the area vertex to cut in.

[0228] In such a case, by the correction process of the area vertex by the broadcast area correction unit 19, by moving the cutting area vertex to a realistic position, a highly accurate broadcast area can be obtained.

[0229] As described above, according to the broadcast area calculation device 1-1 of the first embodiment, in the preprocessing, the broadcast area calculation unit 17 calculates the maximum distance kyori2 based on the effective radiated power ERP of the transmission point and the required electric field min_se, and for each target direction hoko of 360 degrees horizontally with the transmission point as the reference, processes 1a to 2d are performed.

[0230] In process 1a, the broadcast area calculation unit 17 calculates the antenna directivity ant_loss for each angle j in the vertical direction of the transmission antenna, sets the antenna directivity ant_loss at which the gain of the antenna is maximum (loss is minimum) as a_loss, and calculates the maximum distance kyori based on the maximum distance kyori2 and the antenna directivity a_loss.

[0231] As a result, considering the minimum loss due to the antenna directivity ant_loss, the maximum distance kyori is obtained from the maximum distance kyori2.

[0232] In process 1b, the broadcast area calculation unit 17 calculates the electric field E for each profile point between the transmission point and the virtual reception point corresponding to the maximum distance kyori, and calculates the number of profile points p_count and the number of steps p_step. Then, the broadcast area calculation unit 17 corrects the number of steps p_step according to the mesh size to be used.

[0233] As a result, the number of steps p_step calculated in Process 1b is used for setting the designated point when performing processing for each designated point that is coarser than the profile point in Process 1c, and it is possible to reduce the processing load and speed up the processing. Also, since the number of steps p_step does not become larger than necessary according to the mesh size, the calculation in Process 1c does not become coarse, and the calculation accuracy can be ensured.

[0234] In Process 1c, the broadcast area calculation unit 17 sets a designated point for each profile point with an interval of the number of steps p_step from the virtual reception point toward the transmission point, and determines whether the electric field E at the designated point is equal to or greater than the required electric field min_se. When it is determined that the electric field E at the designated point is equal to or greater than the required electric field min_se, the number of steps p_step is added to the designated point, and the profile point indicated by the addition result is set as the maximum point max_pt. Then, the broadcast area calculation unit 17 corrects the maximum point max_pt according to the effective radiated power ERP of the transmission point.

[0235] As a result, processing is performed from the virtual reception point toward the transmission point, and the profile point at which it is first determined that the electric field E is equal to or greater than the required electric field min_se is set as the maximum point max_pt. Therefore, compared with the processing from the transmission point toward the virtual reception point, it is possible to reduce the processing load and speed up the processing.

[0236] Also, since processing is performed for each profile point (each designated point) with an interval of the number of steps p_step, it is possible to reduce the processing load and speed up the processing compared with the processing for each profile point. Furthermore, when the distance from the transmission point to the maximum point max_pt is shorter than the distance preset according to the effective radiated power ERP of the transmission point, the maximum point max_pt is corrected to the profile point corresponding to the distance. For this reason, the maximum point max_pt can be set as an appropriate point according to the effective radiated power ERP of the transmission point.

[0237] In process 1d, the broadcast area calculation unit 17 averages the electric field E between the transmission point and the maximum point max_pt, and sets the electric field E = 0 between the profile points after the maximum point max_pt and the virtual reception point.

[0238] Thereby, between the transmission point and the maximum point max_pt, fluctuations in the electric field E due to slight undulations of the terrain at short distances can be absorbed. Also, the profile points between the maximum point max_pt and the virtual reception point can be excluded from the processing target, reducing the processing load and speeding up the processing.

[0239] In process 2a, the broadcast area calculation unit 17 calculates the maximum width max1 at which the electric field E is equal to or greater than the required electric field min_se from the transmission point toward the maximum point max_pt, and sets the farthest point max_p.

[0240] Thereby, since the profile points between the maximum point max_pt and the virtual reception point are excluded from the processing target, the processing load can be reduced and the processing can be speeded up.

[0241] In process 2b, the broadcast area calculation unit 17 calculates the maximum width max2 at which the electric field E is less than the required electric field min_se from the transmission point toward the farthest point max_p, and sets the farthest point min_p.

[0242] Thereby, since the profile points between the farthest point max_p and the virtual reception point are excluded from the processing target, the processing load can be reduced and the processing can be speeded up.

[0243] In process 2c, when the maximum width max2 is wider than a predetermined value, the broadcast area calculation unit 17 re-sets the farthest point max_p from the transmission point toward the farthest point min_p with the same processing as in process 2a.

[0244] As a result, an appropriate maximum distance point max_p can be obtained instead of an inappropriate maximum distance point max_p. Also, since the profile points between the minimum distance point min_p and the virtual reception point are not subject to processing, it is possible to reduce the processing load and speed up the processing.

[0245] In process 2d, when the maximum distance point max_p is closer to the transmission point than the minimum distance point min_p (when the maximum distance point max_p is reset in process 2c), the broadcast area calculation unit 17 calculates the maximum width dspan at which the electric field E is less than the required electric field min_se and the width A at which the electric field E is greater than or equal to the required electric field min_se from the maximum distance point max_p toward the maximum point max_pt. When the width A exceeds 1.5 times the maximum width dspan, the profile point closest to the maximum point max_pt at the location of the width A is set as the area vertex coordinates area_data[hoko].ido,keido. Also, when the maximum distance point max_p is not closer to the transmission point than the minimum distance point min_p, the broadcast area calculation unit 17 sets the maximum distance point max_p as the area vertex coordinates area_data[hoko].ido,keido.

[0246] As a result, since the profile points between the maximum point max_pt and the virtual reception point are not subject to processing, it is possible to reduce the processing load and speed up the processing. Also, it is possible to ignore building shadows and the like where the electric field E is less than the required electric field min_se and exists between the transmission point and the width A, and it is possible to set highly accurate area vertex coordinates area_data[hoko].ido,keido.

[0247] The broadcast area correction unit 19 corrects the area vertex coordinates area_data[hoko].ido,keido, such as eliminating the protrusion and indentation of the area vertices, so that the shape (the shape of the broadcast area) formed by connecting the area vertex group at the area vertex coordinates area_data[hoko].ido,keido set by the broadcast area calculation unit 17 becomes smooth.

[0248] The broadcast area drawing unit 20 generates a display signal for drawing the broadcast area on the map based on the corrected area vertex coordinates area_data[hoko].ido, keido, and outputs the display signal to the display device 2.

[0249] Therefore, the broadcast area that satisfies the required electric field min_se can be calculated with high accuracy and at high speed.

[0250] 〔Example 2〕 Next, the broadcast area calculation device of Example 2 will be described. The broadcast area calculation device of Example 2 is characterized in that, in the broadcast area calculation device 1-1 of Example 1, the broadcast area is corrected using land use data for each mesh so that the broadcast area does not include sea areas.

[0251] According to Example 2, since a broadcast area that does not include sea areas is set, areas where people do not live can be excluded from the broadcast area.

[0252] FIG. 29 is a block diagram showing a configuration example of the broadcast area calculation device of Example 2. This broadcast area calculation device 1-2 includes a required electric field input unit 10, a constant storage unit 11, a transmission point information storage unit 12, a terrain height data storage unit 13, a land reflection coefficient storage unit 14, a land use data storage unit 15, a land reflection coefficient calculation unit 16, a broadcast area calculation unit 17, a broadcast area information storage unit 18, a broadcast area correction unit 21, and a broadcast area drawing unit 20.

[0253] Comparing the broadcast area calculation device 1-1 of Example 1 shown in FIG. 1 with the broadcast area calculation device 1-2 of Example 2, the broadcast area calculation device 1-2 is different from the broadcast area correction unit 19 provided in the broadcast area calculation device 1-1 in that it includes a different broadcast area correction unit 21. The two broadcast area calculation devices 1-1 and 1-2 have the same constituent parts except for the broadcast area correction units 19 and 21. In FIG. 29, the parts common to FIG. 1 are denoted by the same reference numerals as in FIG. 1, and detailed descriptions thereof are omitted.

[0254] The broadcast area correction unit 21 reads the area vertex coordinates area_data[hoko].ido, keido, which are the broadcast area information, from the broadcast area information storage unit 18. Then, similar to the broadcast area correction unit 19 shown in FIG. 1, the broadcast area correction unit 21 corrects the area vertex coordinates area_data[hoko].ido, keido, such as eliminating the protrusion and indentation of the area vertices, so that the shape formed by connecting the area vertex group (the shape of the broadcast area) becomes smooth.

[0255] The broadcast area correction unit 21 reads the land use data at the positions of the corrected area vertex coordinates area_data[hoko].ido, keido from the land use data storage unit 15. Then, when the land use data is for a sea area, the broadcast area correction unit 21 relocates the area vertices to the transmitter side so that the area vertices do not enter the sea area mesh, thereby re-correcting the area vertex coordinates area_data[hoko].ido, keido.

[0256] The broadcast area correction unit 21 outputs the re-corrected area vertex coordinates area_data[hoko].ido, keido to the broadcast area drawing unit 20.

[0257] FIG. 30 is a flowchart showing an example of the processing of the broadcast area correction unit 21 in the second embodiment (corresponding to step S203). Since the processing in steps S3001 to S3004 is the same as the processing in steps S1901 to S1904 in FIG. 19, the description is omitted here.

[0258] The broadcast area correction unit 21 proceeds from step S3004 and reads the land use data of the area vertices indicated by the area vertex coordinates area_data[hoko].ido, keido from the land use data storage unit 15 (step S3005).

[0259] When the land use data of the area vertex is sea area, the broadcast area correction unit 21 moves the area vertex toward the transmission point so that the area vertex does not enter the mesh of the sea area (step S3006), and sets the coordinates area_data[hoko].ido, keido of the moved area vertex.

[0260] Specifically, when the land use data of the area vertex is sea area, the broadcast area correction unit 21 moves the area vertex toward the transmission point so that the area vertex does not enter the mesh corresponding to the read land use data (sea area), and reads the land use data of the area vertex after movement from the land use data storage unit 15.

[0261] When the land use data of the area vertex is sea area, the broadcast area correction unit 21 moves the area vertex toward the transmission point again so that the area vertex does not enter the mesh of the sea area. The broadcast area correction unit 21 repeats such processing until the area vertex does not enter the mesh of the sea area, identifies the area vertex whose land use data is other than the sea area, and sets the coordinates area_data[hoko].ido, keido of the moved area vertex.

[0262] The broadcast area correction unit 21 proceeds from step S3006 and outputs the coordinates area_data[hoko].ido, keido of the moved area vertex to the broadcast area drawing unit 20 as the broadcast area information after correction (step S3007).

[0263] As described above, according to the broadcast area calculation device 1-2 of the second embodiment, the broadcast area correction unit 21 reads the land use data at the position of the coordinates area_data[hoko].ido, keido of the area vertex from which the protrusion and indentation of the area vertex have been eliminated and so on from the land use data storage unit 15. Then, when the land use data is sea area, the broadcast area correction unit 21 moves the area vertex toward the transmission point so that the land use data of the area vertex becomes other than the sea area, and re-corrects the coordinates area_data[hoko].ido, keido of the area vertex.

[0264] As a result, the same effects as those of the first embodiment are achieved. In addition, since a broadcast area that does not include the sea area is set, areas where no people live can be excluded from the broadcast area.

[0265] Incidentally, the broadcast area correction unit 21 may read the land reflection coefficient at the positions of the corrected area vertex coordinates area_data[hoko].ido, keido from the land reflection coefficient storage unit 14, and determine whether the positions of the corrected area vertex coordinates area_data[hoko].ido, keido are sea areas based on the land reflection coefficient. When the broadcast area correction unit 21 determines that the positions of the corrected area vertex coordinates area_data[hoko].ido, keido are sea areas, the area vertices are moved to the transmitter side so that the area vertices do not enter the mesh of the sea area, thereby re-correcting the area vertex coordinates area_data[hoko].ido, keido.

[0266] 〔Third Embodiment〕 Next, the broadcast area calculation device of the third embodiment will be described. The broadcast area calculation device of the third embodiment is characterized in that, in the broadcast area calculation device 1-1 of the first embodiment, when calculating the broadcast area, the area of the mesh where the land use data indicates the sea area is excluded from the processing target.

[0267] According to the third embodiment, since the area of the mesh indicating the sea area is excluded from the processing target, the broadcast area can be calculated at high speed, and since a broadcast area that does not include the sea area is set, areas where no people live can be excluded from the broadcast area.

[0268] FIG. 31 is a block diagram showing a configuration example of the broadcast area calculation device of the third embodiment. This broadcast area calculation device 1-3 includes a required electric field input unit 10, a constant storage unit 11, a transmitter point information storage unit 12, a terrain height data storage unit 13, a land reflection coefficient storage unit 14, a land use data storage unit 15, a land reflection coefficient calculation unit 16, a broadcast area calculation unit 22, a broadcast area information storage unit 18, a broadcast area correction unit 19, and a broadcast area drawing unit 20.

[0269] When comparing the broadcast area calculation device 1-1 of Example 1 shown in FIG. 1 with the broadcast area calculation device 1-3 of Example 3, the broadcast area calculation device 1-3 is different from the broadcast area calculation device 1-1 in that it includes a broadcast area calculation unit 22 different from the broadcast area calculation unit 17 provided in the broadcast area calculation device 1-1. Both broadcast area calculation devices 1-1 and 1-3 have the same constituent parts except for the broadcast area calculation units 17 and 22. In FIG. 31, the parts common to FIG. 1 are denoted by the same reference numerals as in FIG. 1, and detailed descriptions thereof are omitted.

[0270] Similar to the broadcast area calculation unit 17 shown in FIG. 1, when the broadcast area calculation unit 22 receives a start instruction from the required electric field input unit 10, it starts the broadcast area calculation process. The broadcast area calculation unit 22 uses the required electric fields syoyou_e, syoyou_e2, the number of steps in the angular direction hoko_step, the transmission point information, the terrain height data for each mesh of a predetermined size, the land reflection coefficient, etc., and excludes the areas of the meshes where the land use data indicates a sea area from the processing targets, and calculates the electric field E in the horizontal 360-degree direction with respect to the transmission point, etc., to calculate the broadcast area where the electric field E at the reception point satisfies the required electric field min_se, thereby obtaining the area vertex coordinates area_data[hoko].ido, keido.

[0271] The broadcast area calculation unit 22 stores the area vertex coordinates area_data[hoko].ido, keido in the broadcast area information storage unit 18 as broadcast area information.

[0272] Specifically, for each target direction hoko, the broadcast area calculation unit 22 reads out the land use data for each mesh including the profile point from the land use data storage unit 15 for each profile point between the transmission point and the virtual reception point corresponding to the maximum distance kyori.

[0273] When executing the profile calculation in step S903 of process 1b shown in FIG. 9, the maximum point setting unit 31 of the broadcast area calculation unit 22 determines whether the land use data is a sea area for each profile point.

[0274] When the maximum point setting unit 31 determines that the land use data of the profile point is not a sea area, it calculates the electric field E of the profile point. On the other hand, when the maximum point setting unit 31 determines that the land use data of the profile point is a sea area, it skips the profile point without calculating the electric field E of the profile point and proceeds to the processing of the next profile point.

[0275] The maximum point setting unit 31 and the farthest point setting unit 32 exclude from the processing target the profile points for which it is determined that the land use data is a sea area and the electric field E is not calculated.

[0276] That is, when setting the designated point in step S1001 of process 1c shown in FIG. 10, the maximum point setting unit 31 does not set as the designated point the profile points for which it is determined that the land use data is a sea area and the electric field E is not calculated. That is, for the profile points for which it is determined that the land use data is a sea area and the electric field E is not calculated, the processes of steps S1002 and S1003 are not performed.

[0277] Also, in process 1d shown in FIG. 11, the maximum point setting unit 31 excludes from the processing targets of steps S1102 to S1104 the profile points for which it is determined that the land use data is a sea area and the electric field E is not calculated.

[0278] Also, in process 2a shown in FIG. 13, process 2b shown in FIG. 14, and process 2c shown in FIG. 15, the farthest point setting unit 32 excludes from the processing targets of steps S1301, S1401, and S1502 the profile points for which it is determined that the land use data is a sea area and the electric field E is not calculated (the processing is performed so that the maximum width max1 etc. do not include the profile points). As a result, there will be no profile points in the maximum widths max1, max2, max3 for which the land use data is a sea area, and no profile points for which the land use data is a sea area will be set as the farthest points max_p and min_p.

[0279] Further, when setting the profile points in step S1603 shown in FIG. 16, the farthest point setting unit 32 does not set the profile points for which it is determined that the land use data is a sea area and the electric field E could not be calculated. That is, for the profile points for which it is determined that the land use data is a sea area and the electric field E could not be calculated, the processes in steps S1604 to S1607 of the profile points are not performed (the processes are performed so as not to include the profile points in the maximum width dspan and the width A). As a result, there will be no profile points in the maximum width dspan and the width A for which the land use data is a sea area, and no profile points for which the land use data is a sea area will be set in the area vertex coordinates area_data[hoko].ido, keido.

[0280] As described above, according to the broadcast area calculation device 1-3 of the third embodiment, the broadcast area calculation unit 22 reads the land use data of the profile points from the land use data storage unit 15, and calculates the electric field E for each profile point while excluding the area of the mesh indicating the sea area from the processing target, thereby obtaining the area vertex coordinates area_data[hoko].ido, keido. In this case, the broadcast area calculation unit 22 calculates the electric field E for the profile points where the land use data is not a sea area between the transmission point and the virtual reception point, and does not calculate the electric field E for the profile points where the land use data is a sea area.

[0281] As a result, since the area of the mesh indicating the sea area is excluded from the processing target, the broadcast area can be calculated at a higher speed. In addition, since a broadcast area not including the sea area is set, an area where no one lives can be excluded from the broadcast area.

[0282] Further, the broadcast area calculation unit 22 may read the land reflection coefficient of each profile point from the land reflection coefficient storage unit 14 and determine whether the profile point is a sea area based on the land reflection coefficient. When the broadcast area calculation unit 22 determines that the profile point is a sea area, it performs the same processing as when it is determined that the above-mentioned land use data is a sea area. When it is determined that the profile point is not a sea area, it performs the same processing as when it is determined that the above-mentioned land use data is not a sea area.

[0283] As described above, the present invention has been described with reference to Examples 1 to 3. However, the present invention is not limited to Examples 1 to 3, and various modifications can be made without departing from the technical idea thereof.

[0284] For example, in Examples 1 to 3 described above, the broadcast area calculation devices 1-1 and 1-3 are provided with a broadcast area correction unit 19, and the broadcast area calculation device 1-2 is provided with a broadcast area correction unit 21. The broadcast area correction units 19 and 21 read and correct the broadcast area information from the broadcast area information storage unit 18, and output the corrected broadcast area information to the broadcast area drawing unit 20.

[0285] On the other hand, the broadcast area calculation devices 1-1 and 1-3 may not be provided with the broadcast area correction unit 19, and the broadcast area calculation device 1-2 may not be provided with the broadcast area correction unit 21. In this case, the broadcast area drawing unit 20 reads the broadcast area information from the broadcast area information storage unit 18, generates a display signal, and outputs it to the display device 2. Thereby, the circuit scale and the processing load can be reduced.

[0286] Further, for example, in Examples 1 to 3 described above, the maximum point setting unit 31 of the broadcast area calculation units 17 and 22 calculates the maximum distance kyori from the maximum distance kyori2 in the process 1a shown in FIG. 8, and in the processes 1b shown in FIG. 9 and 1c shown in FIG. 10, etc., each process is performed based on the virtual reception point corresponding to the maximum distance kyori.

[0287] In contrast, the maximum point setting unit 31 may perform each process based on the virtual reception point corresponding to the maximum distance kyori2, using the maximum distance kyori2 instead of the maximum distance kyori. In this case, it is not necessary for the maximum point setting unit 31 to calculate the maximum distance kyori. Thereby, the processing load can be reduced and the processing speed can be increased.

[0288] Also, for example, in the above-described first to third embodiments, the maximum point setting unit 31 of the broadcast area calculation units 17 and 22 performs the process 1d shown in FIG. 11, but it is not necessary to perform the process 1d. In this case, the farthest point setting unit 32 performs the processes 2a to 2d using the electric field E for which the averaging process by the process 1d is not performed.

[0289] Also, for example, in the second embodiment, the broadcast area correction unit 21 of the broadcast area calculation device 1-2 corrects the broadcast area information using the land use data for each mesh so that the broadcast area does not include a sea area. The present invention is not limited to limiting the classification of the land use data to be excluded from the broadcast area to a sea area, and the broadcast area information may be corrected so as not to include areas of classifications other than the sea area, or the broadcast area information may be corrected so as not to include areas of a plurality of classifications such as a sea area or areas of a plurality of classifications other than the sea area.

[0290] Also, for example, in the third embodiment, the broadcast area calculation unit 22 of the broadcast area calculation device 1-3 excludes the area of the mesh in which the land use data indicates a sea area from the processing target when calculating the broadcast area. The present invention is not limited to limiting the land use data to be excluded from the processing target to a sea area, and areas of classifications other than the sea area may be excluded from the processing target, or areas of a plurality of classifications such as a sea area or a plurality of classifications other than the sea area may be excluded from the processing target.

[0291] As for the hardware configuration of the broadcast area calculation devices 1-1 to 1-3 according to the first to third embodiments of the present invention, a normal computer can be used. The broadcast area calculation devices 1-1 to 1-3 are configured by a computer including a CPU, a volatile storage medium such as a RAM, a non-volatile storage medium such as a ROM, and an interface.

[0292] Each function of the required electric field input unit 10, constant storage unit 11, transmission point information storage unit 12, terrain height data storage unit 13, land reflection coefficient storage unit 14, land use data storage unit 15, land reflection coefficient calculation unit 16, broadcast area calculation unit 17, broadcast area information storage unit 18, broadcast area correction unit 19, and broadcast area drawing unit 20 provided in the broadcast area calculation device 1-1 is realized by causing the CPU to execute a program describing these functions.

[0293] Also, each function of the required electric field input unit 10, constant storage unit 11, transmission point information storage unit 12, terrain height data storage unit 13, land reflection coefficient storage unit 14, land use data storage unit 15, land reflection coefficient calculation unit 16, broadcast area calculation unit 17, broadcast area information storage unit 18, broadcast area correction unit 21, and broadcast area drawing unit 20 provided in the broadcast area calculation device 1-2 is realized by causing the CPU to execute a program describing these functions.

[0294] Also, each function of the required electric field input unit 10, constant storage unit 11, transmission point information storage unit 12, terrain height data storage unit 13, land reflection coefficient storage unit 14, land use data storage unit 15, land reflection coefficient calculation unit 16, broadcast area calculation unit 22, broadcast area information storage unit 18, broadcast area correction unit 19, and broadcast area drawing unit 20 provided in the broadcast area calculation device 1-3 is realized by causing the CPU to execute a program describing these functions.

[0295] These programs are stored in the storage medium and read by the CPU for execution. Also, these programs can be stored and distributed in storage media such as magnetic disks (floppy (registered trademark) disks, hard disks, etc.), optical disks (CD-ROM, DVD, etc.), semiconductor memories, and can also be transmitted and received via a network.

Explanation of Signs

[0296] 1-1, 1-2, 1-3 Broadcast area calculation device 2 Display device 10 Required electric field input section 11 Constant storage section 12 Transmission point information storage section 13 Terrain height data storage section 14 Land reflection coefficient storage section 15 Land use data storage section 16 Land reflection coefficient calculation section 17, 22 Broadcast area calculation section 18 Broadcast area information storage section 19, 21 Broadcast area correction section 20 Broadcast area drawing section 30 Preprocessing section 31 Maximum point setting section 32 Farthest point setting section syoyou_e, syoyou_e2, min_se Required electric field hoko_step Number of steps in the angular direction stp Number of steps in the distance direction ERP Effective radiated power of the transmission point kyori2, kyori Maximum distance hoko Target direction a_loss, ant_loss(recv_h) Antenna directivity recv_h Virtual receiving point height for calculation send_h Transmission point height j Angle in the vertical direction hantei_kyori Judgment distance p_count Number of profile points p_step Number of steps E electric field max_pt maximum point max1, max2, max3, dspan maximum width max_p, min_p farthest point area_data[direction].latitude, longitude area vertex coordinates (latitude and longitude)

Claims

1. In a broadcast area calculation device that calculates a broadcast area capable of receiving terrestrial digital broadcasts, a broadcast area calculation unit that calculates the latitude and longitude of the area vertex group of the broadcast area that satisfies a predetermined required electric field min_se for each target direction hoko obtained by dividing 360 degrees horizontally at predetermined angles with respect to the transmission point of the broadcast station, and sets them as area vertex coordinates area_data[hoko].ido, keido; The broadcast area calculation unit includes: a preprocessing unit that calculates the maximum distance kyori2 of the reception point by free space propagation based on the effective radiated power ERP of the transmission point, which is the effective radiated power of the radio wave transmitted from the antenna of the broadcast station, and the required electric field min_se; calculates the electric field E for each profile point between the transmission point and the virtual reception point, where the virtual reception point is the reception point corresponding to the maximum distance kyori2 calculated by the preprocessing unit; a maximum point setting unit that determines, for each profile point from the virtual reception point toward the transmission point, whether the electric field E is equal to or greater than the required electric field min_se, and sets the profile point at which the electric field E is first determined to be equal to or greater than the required electric field min_se as the maximum point max_pt; A broadcast area calculation device, characterized in that the maximum point max_pt is set as the area vertex coordinates area_data[hoko].ido, keido.

2. In the broadcast area calculation device according to Claim 1, further comprising a farthest point setting unit that sets the farthest point; The farthest point setting unit includes: calculates the maximum width max1 at which the electric field E becomes equal to or greater than the required electric field min_se from the transmission point toward the maximum point max_pt set by the maximum point setting unit, and sets the profile point closest to the maximum point max_pt at the point of the maximum width max1 as the farthest point max_p; calculates the maximum width max2 at which the electric field E becomes less than the required electric field min_se from the transmission point toward the farthest point max_p, and sets the profile point closest to the farthest point max_p at the point of the maximum width max2 as the farthest point min_p; determines whether the maximum width max2 is wider than a predetermined value, and if it is determined that the maximum width max2 is not wider than the predetermined value, sets the coordinates of the farthest point max_p as the area vertex coordinates area_data[hoko].ido, keido. When it is determined that the maximum width max2 is wider than a predetermined value, the maximum width max3 at which the electric field E is equal to or greater than the required electric field min_se is calculated from the transmission point toward the farthest point min_p, and the profile point closest to the farthest point min_p at the point of the maximum width max3 is reset to the farthest point max_p and set to the area vertex coordinates area_data[hoko].ido, keido. From the farthest point max_p toward the maximum point max_pt, the width at which the electric field E becomes less than the required electric field min_se is sequentially calculated, and the maximum width is set as the maximum width dspan. When the width is larger than the set maximum width dspan, the maximum width dspan is updated. The width A at which the electric field E is equal to or greater than the required electric field min_se is calculated. When the width A exceeds a predetermined multiple of the maximum width dspan, the profile point closest to the maximum point max_pt at the point of the width A is set as the area vertex coordinates area_data[hoko].ido, keido. A broadcast area calculation device characterized by this.

3. In the broadcast area calculation device according to claim 1 or 2, Furthermore, it is characterized by including a broadcast area correction unit that averages the positions of the area vertex coordinates area_data[hoko].ido, keido of a predetermined number of adjacent ones for each target direction hoko calculated by the broadcast area calculation unit.

4. In the broadcast area calculation device according to any one of claims 1 to 3, The maximum point setting unit, For each of the profile points between the transmission point and the maximum point max_pt, an average value is calculated based on the electric field E of a plurality of consecutive profile points including the profile point, and the average value is set as the electric field E of the profile point. A broadcast area calculation device characterized by this.

5. In the broadcast area calculation device according to any one of claims 1 to 4, The maximum point setting unit, The antenna directivity ant_loss is calculated for each predetermined angle j in the vertical direction of the antenna of the broadcast station, the antenna directivity ant_loss at which the gain of the antenna is maximum is set as the antenna directivity a_loss, and based on the maximum distance kyori2 and the antenna directivity a_loss, the maximum distance kyori is calculated. Using the maximum distance kyori instead of the maximum distance kyori2, setting the reception point corresponding to the maximum distance kyori as the virtual reception point, and setting the maximum point max_pt, a broadcast area calculation device characterized by this.

6. In the broadcast area calculation device according to claim 3, further comprising a land use data storage unit that stores land use data for each mesh of a predetermined size, the broadcast area correction unit, reads out the land use data at the positions of the averaged area vertex coordinates area_data[hoko].ido, keido from the land use data storage unit, and when the land use data is a sea area, moves the positions of the averaged area vertex coordinates area_data[hoko].ido, keido to the transmission point side so that the area vertices indicated by the averaged area vertex coordinates area_data[hoko].ido, keido do not enter the mesh of the sea area, a broadcast area calculation device characterized by this.

7. In the broadcast area calculation device according to any one of claims 1 to 5, further comprising a land use data storage unit that stores land use data for each mesh of a predetermined size, the maximum point setting unit, reads out the land use data of the profile points between the transmission point and the virtual reception point from the land use data storage unit, determines whether the land use data of the profile points is a sea area, calculates the electric field E for the profile points when the land use data is not the sea area, a broadcast area calculation device characterized by this.

8. A computer that configures a broadcast area calculation device that calculates the latitude and longitude of the area vertex group of the broadcast area that satisfies a predetermined required electric field min_se for each target direction hoko obtained by dividing 360 degrees horizontally at predetermined angles with respect to the transmission point of the broadcast station as area vertex coordinates area_data[hoko].ido, keido, a preprocessing unit that calculates the maximum distance kyori2 of the reception point by free space propagation based on the effective radiated power ERP of the transmission point, which is the effective radiated power of the radio wave transmitted from the antenna of the broadcast station, and the required electric field min_se, and calculates the electric field E for each profile point between the transmission point and the virtual reception point using the reception point corresponding to the maximum distance kyori2 calculated by the preprocessing unit as the virtual reception point, For each of the profile points, determine whether the electric field E is greater than or equal to the required electric field min_se from the virtual reception point towards the transmission point, and function as a maximum point setting unit that sets the profile point at which it is first determined that the electric field E is greater than or equal to the required electric field min_se as the maximum point max_pt. A program characterized by setting the maximum point max_pt to the area vertex coordinates area_data[hoko].ido, keido.

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