Terrain correction method determination device, terrain correction method determination method, and program

Abstract

Provided is a terrain correction method determination device that, on the basis of the planar distance between a reference point and an evaluation object point, classifies terrain information on a spot between the reference point and the evaluation object point in accordance with the planar distance to the reference point, classifies the spot into a plurality of groups and determines, for each group, a terrain correction method on the basis of the terrain type of the group, and further determines a terrain correction method for the entire group when the terrain type of the group includes a plurality of specific terrain types.

Description

Terrain correction method determination device, terrain correction method determination method and program

[0001] The present invention relates to a terrain correction method determination device, a terrain correction method determination method, and a program.

[0002] In wireless communications, when creating a received power level map or the like, an equation is used to estimate radio wave propagation characteristics, including terrain correction. Non-Patent Document 1 explains propagation characteristics in irregular terrain such as hilly terrain, isolated mountains, multiple mountains, sloping terrain, and mixed land-sea propagation paths. Non-Patent Document 2 explains the Okumura-Hata equation, which is a propagation characteristic estimation equation.

[0003] Patent No. 5845198

[0004] Edited by Yoshihisa Okumura and Masaaki Shinji: "Fundamentals of Mobile Communications", edited by the Institute of Electronics, Information and Communication Engineers (1986 / 10 / 01), published by Coronasha, A5 size, pp. 47-53, ISBN: 978-4-88552-065-5, https: / / www.coronasha.co.jp / np / isbn / 9784885520655 / 2.6 Land Mobile Propagation 2.6.3 Propagation Characteristics in Irregular Terrain Antenna and Propagation Research Committee (A.P.) Okumura-Hata Formula https: / / www.ieice.org / cs / ap / misc / denpan-db / prop_model_db / model_list / okumura-hata-formula /

[0005] There are terrains having different types of irregular terrain characteristics as described in Non-Patent Document 1. A terrain correction method for terrains having different types of irregular terrain characteristics is not clearly disclosed in prior art documents such as Patent Document 1 and Non-Patent Documents 1 and 2. The present invention aims to determine an appropriate terrain correction method for terrains having multiple irregular terrain characteristics.

[0006] One aspect of the present invention is a terrain correction method determination device that classifies terrain information of points between a reference point and an evaluation point according to their planar distance from the reference point, divides the points into multiple groups, determines a terrain correction method for each group based on the terrain type of the group, and if the terrain type of the group includes multiple specific terrain types, further determines a terrain correction method for the entire group.

[0007] The terrain correction method determination device, terrain correction method determination method, and program of the present invention can determine an appropriate terrain correction method for terrain having a plurality of irregular terrain characteristics.

[0008] FIG. 1 is a diagram showing a terrain correction method determination device according to the present embodiment; FIG. 2 is a terrain profile created based on the planar distance from a reference point and the altitude included in the terrain information; FIG. 3 is an example showing terrain information for each point; FIG. 4 is a diagram showing points determined to be inflection points or water surfaces extracted by a terrain information analysis unit; FIG. 5 is a flowchart showing a method for extracting points that are undulation peaks or valley points; FIG. 6 is a flowchart showing an example of a method for extracting points that are undulation peaks or valley points; FIG. 7 is a flowchart showing the operation of the terrain correction method determination device; FIG. 8 is a flowchart showing a method for determining terrain type; FIG. 9 is a flowchart showing a method for calculating a correction value K using the land-sea mixed passage correction method; ＳＲ / d,d ＳＴ / d), the planar distance d between the reference point and the evaluation point, and the correction value K in the land-sea mixed passage correction ｓ This is a graph showing the relationship between H and d when H=200m. １ , d ２ , K. ｉｍ ΣH and K ｍｍ 10 is a graph showing the relationship between the terrain undulation height Δh and the hill correction value K ｈ 10 is a graph showing the relationship between the terrain undulation height Δh and the hill fine correction value K ｈｆ 10 is a graph showing the relationship between the planar distance d between the reference point and the evaluation point and the inclination angle θ between the reference point and the evaluation point. ｍ and the slope correction value K ｓｐ10 is a graph showing the relationship between the correction value calculated by each terrain correction method and the correction value calculated by each terrain correction method.

[0009] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing a terrain correction method determination device 1 according to this embodiment. The terrain correction method determination device 1 includes a terrain information acquisition unit 11, a terrain information analysis unit 12, a terrain type determination unit 13, a terrain correction method determination unit 14, and an output unit 15. The terrain information acquisition unit 11 acquires terrain information. The terrain information is information about each point between a predetermined reference point and an evaluation point to be evaluated. The reference point is the location of a base station.

[0010] The topographical information includes information on the planar distance from a reference point to each point. The planar distance is the distance between two points when altitude is ignored, and is the straight-line distance between two points on a flat map. The planar distance is a value calculated, for example, based on the latitude and longitude of the two points.

[0011] The topographical information includes elevation information for each point. The topographical information includes location information for each point (e.g., longitude and latitude for each point). The topographical information includes land use type information for each point. The land use type information is, for example, land use subdivision mesh data provided by the Ministry of Land, Infrastructure, Transport and Tourism, and indicates, for example, whether the land use type is river land, lakes, marshes, or seawater.

[0012] Figure 2 shows a terrain profile created based on the planar distance and altitude from a reference point included in the terrain information. The terrain profile shown in Figure 2 is a terrain profile between the reference point and an evaluation point located 10,000 m from the reference point.

[0013] 3 shows an example of topographical information for each point, which is associated with the planar distance from the reference point, altitude, location information, and land use type information for each point.

[0014] The topographical information analysis unit 12 analyzes the topographical information and determines that, among all points between the reference point and the evaluation point, points whose land use type is related to water (rivers, lakes, marshes, and sea areas) are water surfaces.

[0015] The topographic information analysis unit 12 extracts points that are, for example, undulation peaks or valleys. FIG. 5 is a flowchart showing a method for extracting points that are undulation peaks or valleys. The topographic information analysis unit 12 calculates the difference in elevation and the slope between adjacent points (step S121). The topographic information analysis unit 12 extracts points where the slope changes from positive to negative as inflection points (step S122). The topographic information analysis unit 12 extracts points where the slope changes from positive to negative as undulation peaks, and points where the slope changes from negative to positive as valleys (step S123). Points where the slope changes from positive to zero or from zero to positive include points where the slope changes from negative to zero or from zero to positive.

[0016] Note that if the slope changes from positive to 0 and then changes from 0 to positive, the topographic information analysis unit 12 does not need to extract those two points as inflection points. Also, if the slope changes from negative to 0 and then changes from 0 to negative, the topographic information analysis unit 12 does not need to extract those two points as inflection points.

[0017] When two adjacent points are both extracted as inflection points, and the absolute value of the slope between those two points is equal to or less than a predetermined value, the topographic information analysis unit 12 may exclude those two inflection points from the inflection points to be extracted. This is because when the absolute value of the slope between two points is equal to or less than a predetermined value, the two inflection points can be considered to be points located midway along an upslope or downslope. When the difference in height between an adjacent undulation vertex is equal to or less than a predetermined value, the topographic information analysis unit 12 may exclude that undulation vertex from the undulation vertices to be extracted. When the difference in height between an adjacent valley point is equal to or less than a predetermined value, the topographic information analysis unit 12 may exclude that valley point from the valley points to be extracted. When the difference in height between an adjacent undulation vertex and valley point is equal to or less than a predetermined value, the undulation vertex and valley point may be excluded from the undulation vertices and valley points to be extracted.

[0018] FIG. 6 is a flowchart showing an example of a method for extracting points that are ridge peaks or valleys. The topographic information analysis unit 12 calculates the difference in elevation and the slope between adjacent points (step S121a). The topographic information analysis unit 12 extracts points where the slope changes from positive to negative as inflection points (step S122a). The topographic information analysis unit 12 excludes adjacent inflection points whose elevation difference is equal to or less than a predetermined value (step S123a). The topographic information analysis unit 12 excludes, from the remaining inflection points, inflection points where the slopes of adjacent inflection points are the same (step S124a). The topographic information analysis unit 12 calculates the slopes of adjacent inflection points among the remaining inflection points, and extracts points where the slope changes from positive to negative as inflection points (step S125a). The topographical information analysis unit 12 extracts points where the slope changes from positive to negative as undulation peaks, and extracts points where the slope changes from negative to positive as valleys.

[0019] 6, it is not necessary to repeat the same processing step, that is, the extraction operation, many times, and therefore it is possible to extract inflection points with fewer processing times.

[0020] The topographical information analysis unit 12 calculates the slope angle between the reference point and the evaluation target point, and the slope angle between the reference point and the inflection point.

[0021] FIG. 4 is a diagram showing inflection points extracted by the topographical information analysis unit 12 and points determined to be water surfaces.

[0022] The terrain type determination unit 13 determines the type of terrain based on the analysis results by the terrain information analysis unit 12. The method for determining the type of terrain will be described later. When the planar distance between the reference point and the evaluation point is equal to or greater than a predetermined distance, the terrain type determination unit 13 divides the section between the reference point and the evaluation point, groups the points included in each section, and determines the type of terrain for each group based on the terrain information of the points included in each group. The predetermined distance for determining the length of the section is, for example, twice the minimum distance for which the type of terrain can be determined. For example, when the predetermined distance for determining the length of the section is 5 km and the planar distance between the reference point and the evaluation point is 12 km, the terrain type determination unit 13 divides the section into two sections with a planar distance of 6 km. The section between the reference point and the evaluation point may be divided into three or more sections in a similar manner depending on the length of the planar distance between the reference point and the evaluation point, and the sections may be classified into three or more groups, including a third group and a fourth group.

[0023] The terrain correction method determination unit 14 determines a terrain correction method based on the terrain correction method determined by the terrain type determination unit 13. The method for determining the terrain correction method will be described later.

[0024] The output unit 15 outputs the terrain correction method determined by the terrain correction method determination unit 14 to the correction value calculation device 2 .

[0025] FIG. 7 is a flowchart showing the operation of the terrain correction method determination device 1. The terrain information acquisition unit 11 acquires terrain information (step S11). The terrain information analysis unit 12 analyzes the terrain information (step S12). When the planar distance between the reference point and the evaluation point is shorter than a predetermined distance (step S13: YES), the terrain type determination unit 13 determines the type of terrain based on the analysis results between the reference point and the evaluation point (step S14). When the planar distance between the reference point and the evaluation point is equal to or greater than a predetermined distance (step S13: NO), the terrain type determination unit 13 divides the section between the reference point and the evaluation point and separates the points included in each section into groups (step S15). The terrain type determination unit 13 determines the type of terrain for each group (step S16). When the terrain type determination unit 13 divides the section between the reference point and the evaluation point if the distance is equal to or greater than twice the minimum distance at which the type of terrain can be determined, all of the divided sections can be set as sections with planar distances at which the type of terrain can be determined.

[0026] The terrain correction method determination unit 14 determines a terrain correction method based on the type of terrain (step S17). The output unit 15 outputs the terrain correction method to the correction value calculation device 2 (step S18). Note that the operations do not necessarily have to be performed in this order, and the terrain correction method determination device 1 may analyze terrain information as necessary when determining the type of terrain.

[0027] The correction value calculation device 2 calculates a correction value K based on the terrain correction method determined by the terrain correction method determination device 1. The correction value calculation device 2 outputs the calculated correction value K. The calculation method of the correction value K, which differs depending on the terrain correction method, will be described later. The correction value K is a value added to the propagation loss L in the Okumura-Hata formula described in Non-Patent Document 2. In the Okumura-Hata formula, the received power P Ｒ is calculated using formula (1).

[0028] In formula (1), P Ｔ is the transmission power, G Ｔ is the transmit antenna gain, L Ｆ is the power supply loss, G Ｒis the receiving antenna gain, and L is the propagation loss. L is usually calculated by equation (2).

[0029] In equation (2), f is the frequency, h ｂ is the antenna height at the reference point, d is the distance between the transmitter and receiver, h ｍ is the antenna height at the evaluation point, α(h ｍ ) is the height characteristic of the evaluation point. ｍ ) is calculated by equation (3) when the location is a small or medium-sized city, by equation (4) when the location is a large city and the frequency f is 200 MHz or less, and by equation (5) when the location is a large city and the frequency f is 400 MHz or more.

[0030] In addition, when the location is a suburban area or an open area, the correction shown in Equation (6) and Equation (7) is performed, and the propagation loss in the suburban area L ｐｓ , propagation loss in open areas L ｐｏ Calculate.

[0031] The correction value calculation device 2 may be realized as the same device as the terrain correction method determination device 1. Furthermore, the correction value calculation device 2 may refer to the terrain information or the analysis results of the terrain information as necessary when calculating the correction value.

[0032] When the interval between the reference point and the evaluation point is divided and the points included in each interval are divided into multiple groups, the correction value calculation device 2 calculates the relationship between the transmission power and the reception power using the two most distant points in each interval as the reference point and the evaluation point.The correction value calculation device 2 then calculates the reception power at the final evaluation point based on the relationship between the transmission power and the reception power in each interval.

[0033] A specific example of the calculation method will be described below. The group of sections closest to the reference point is called the first group. First, the transmission power P Ｔ１ and received power P Ｒ１The relationship between the first and second groups is calculated using equation (1). Ｔ２ and received power P Ｒ２ The relationship between the transmission power P Ｔ２ is the received power P in the first group Ｒ１ This calculation is repeated up to the last group to calculate the final received power. In other words, the correction value K calculated for each section and the propagation loss L are used to calculate the amount of power attenuated in each section, and the final received power is calculated. Note that the received power P Ｒ１ and transmission power P Ｔ２ For each receiving antenna gain G Ｒ１ and the transmitting antenna gain G Ｔ２ Therefore, the received power P Ｒ１ and transmission power P Ｔ２ (In a group divided into three or more sections, the transmission power of the first group and the reception power of the last group are all excepted) must be treated as the field strength, and the above calculations must be performed using true values.

[0034] The method by which the terrain type determination unit 13 determines the type of terrain will be described below. When the ratio of points that are water surface to all points between the reference point and the evaluation point is equal to or greater than a certain level, the terrain type determination unit 13 determines the type of terrain to be a land-sea mixed passage, a mountainous area above water surface, or a multi-water surface slope. Mountainous areas above water surface and a multi-water surface slope will be described later. Hereinafter, the ratio of points that are water surface to all points between the reference point and the evaluation point is equal to or greater than a certain level, which is defined as condition C1. Condition C1 means, for example, that the ratio of points that are water surface to all points between the reference point and the evaluation point is 40% or more. The ratio of points that are water surface to all points between the reference point and the evaluation point being equal to or greater than a certain level is defined as the number C of points that are determined to be water surface. ｄｓ The number of all points in C ｄａ Ratio to (C ｄｓ / C ｄａ ) is above a certain level.

[0035] The terrain type determination unit 13 determines the terrain type to be mountainous when condition C1 is not satisfied, the elevation difference between the reference point and the maximum elevation point is equal to or greater than a predetermined value, and the planar distance between the maximum elevation point and the peak of the mountain is equal to or less than a certain value. The maximum elevation point is the point with the highest elevation of all points between the reference point and the evaluation point. Hereinafter, condition C2 refers to the elevation difference between the reference point and the maximum elevation point being equal to or greater than a predetermined value, and the planar distance between the maximum elevation point and the peak of the mountain being equal to or less than a certain value. Condition C2, for example, refers to the elevation difference between the reference point and the maximum elevation point being equal to or greater than 110 m, and the planar distance between the maximum elevation point and the peak of the mountain being equal to or less than a certain value.

[0036] The terrain type determination unit 13 calculates the planar distance between the maximum elevation point and the mountain peak from the information on the maximum elevation point and the latitude and longitude, and the list information on the latitude and longitude of the mountain peak, and determines the shortest planar distance l ｍｔ is equal to or less than a certain value, it is determined that the planar distance between the maximum elevation point and the summit of the mountain is equal to or less than a certain value.

[0037] When conditions C1 and C2 are not met and the number of vertices of the terrain is equal to or greater than a predetermined number, the terrain type determination unit 13 determines the terrain type to be hilly. Hereinafter, the fact that the terrain has a predetermined number of vertices is referred to as condition C3.

[0038] If the conditions C1, C2, and C3 are not satisfied, the terrain type determination unit 13 determines that the angle θ ｍ The angle θ between the reference point and the inflection point ｊ and θ ｍ When the maximum value of the difference ratio is equal to or greater than a predetermined value, the type of terrain is determined to be a sloped terrain. ｍ Angle θ ｊ and θ ｍ The condition C4 is that the maximum value of the ratio of the difference between the values ​​is equal to or greater than a predetermined value. The condition C4 is expressed by the following equation (8).

[0039] R ＴＨ is a predetermined value, for example, 10%.

[0040] If conditions C1, C2, C3, and C4 are not satisfied, the terrain type determination unit 13 determines the terrain type as unclassified. If the terrain type is unclassified, the correction value calculation device 2 calculates the correction value K=0.

[0041] The terrain type determination unit 13 determines the terrain type to be mountainous above water when both conditions C1 and C2 are met. The terrain type determination unit 13 determines the terrain type to be sloped water surface when both conditions C1 and C4 are met.

[0042] 8 is a flowchart showing a terrain type determination method. If condition C1 is satisfied (step S131: YES), the terrain type determination unit 13 determines whether condition C2 is satisfied (step S131-a). If condition C2 is satisfied (step S131-a: YES), the terrain type determination unit 13 determines the terrain type to be mountainous above water (step S132-a). If condition C2 is not satisfied (step S131-a: NO), the terrain type determination unit 13 determines whether condition C4 is satisfied (step S131-b). If condition C4 is satisfied (step S131-b: YES), the terrain type determination unit 13 determines the terrain type to be a multi-water slope (step S132-b). If condition C4 is not satisfied (step S131-b: NO), the terrain type determination unit 13 determines the terrain type to be a land-sea mixed passage (step S132). If condition C1 is not met (step S131: NO) but condition C2 is met (step S133: YES), the terrain type determination unit 13 determines the terrain type to be mountainous (step S134). If condition C2 is not met (step S133: NO) but condition C3 is met (step S135: YES), the terrain type determination unit 13 determines the terrain type to be hilly (step S136). If condition C3 is not met (step S135: NO) but condition C4 is met (step S137: YES), the terrain type determination unit 13 determines the terrain type to be sloping terrain (step S138). If condition C4 is not met (step S137: NO), the correction method is determined to be unclassified (step S139).

[0043] As described above, the flowchart showing the terrain type determination method shown in FIG. 8 classifies terrain based on given terrain information into the following types: above-water mountain, multi-surface slope, land-sea mixed passage, mountain, hilly terrain, sloped terrain, and unclassified. It is also possible to exclude both the above-water mountain processing (steps S131-a and S131-b) and the multi-surface slope processing (steps S132-a and S132-b) from the flowchart and classify the terrain into land-sea mixed passage, mountain, hilly terrain, sloped terrain, and unclassified. Alternatively, a flowchart excluding either above-water mountain or multi-surface slope may be used. This is because both types of terrain are particularly rare, and excluding these types of terrain in most cases (steps S131-a and S131-b) allows for more accurate and somewhat faster terrain classification.

[0044] The terrain type determination unit 13 may determine the terrain type as unclassified when conditions C1 and C2 are not satisfied and the planar distance between the reference point and the evaluation point is equal to or less than a predetermined value. More specifically, the terrain type determination unit 13 may determine the terrain type as unclassified when conditions C1 and C2 are not satisfied and the planar distance between the reference point and the evaluation point is equal to or less than 5 km. The hilly terrain correction is based on the assumption that the planar distance between the reference point and the evaluation point is relatively short (10 km or less), but if the planar distance is even shorter, such as less than 5 km, it falls outside the range in which the hilly terrain correction can be applied (the distance d between the reference point and the evaluation point in the graph showing the hilly terrain correction value in FIG. 13 is 0.05). ＭＲ In addition, the correction value calculated when the terrain is slope terrain correction takes a small value when the planar distance between the reference point and the evaluation point is short (in the graph showing slope terrain correction in Figure 15, when the distance d between the reference point and the evaluation point is < 5 km, the value is on a curve with a smaller slope than the dashed curve where d < 10 km, and the slope terrain correction value K ｓｐ (The difference is only about 1 to 2 dB.) Therefore, when the planar distance between the reference point and the evaluation point is equal to or less than a predetermined value, the type of terrain is determined to be unclassified, thereby reducing the amount of calculation.

[0045] If the conditions C1, C2, and C3 are not satisfied, the terrain type determination unit 13 determines that the slope angle θ ｍ If the slope angle θ is within a predetermined range, the terrain type may be determined to be unclassified. In addition, in determining condition C3, the reference point may be changed to limit the terrain information to be investigated to a range with a shorter planar distance from the evaluation target point. The value in the predetermined range is a range in which the terrain is determined to be not inclined. ｍ If the value is within a predetermined range, a valid correction value cannot be calculated using slope terrain correction. Therefore, the amount of calculation can be reduced by determining the terrain correction method as non-classification.

[0046] The above describes a method for determining the type of terrain based on points between a reference point and an evaluation target point. However, when points are divided into groups, a similar calculation is performed with the reference point being the point in the group with the shortest planar distance from the reference point (hereinafter referred to as the reference point side point), and the evaluation target point being the point in the group with the shortest planar distance from the evaluation target point (hereinafter referred to as the evaluation target point side point), to determine the type of terrain including the grouped points.

[0047] The method for determining the terrain correction method based on the type of terrain will be described below. The terrain correction method determination unit 14 determines the terrain correction method for each group based on the type of terrain. If the terrain type of a group is a land-sea mixed passage, the terrain correction method determination unit 14 determines the terrain correction method for the group to be land-sea mixed passage correction. If the terrain type of a group is mountainous, the terrain correction method determination unit 14 determines the terrain correction method for the group to be mountain correction. If the terrain type of a group is hilly, the terrain correction method determination unit 14 determines the terrain correction method for the group to be hilly correction. If the terrain type of a group is sloped terrain, the terrain correction method determination unit 14 determines the terrain correction method for the group to be sloped terrain correction. If the terrain type of a group is unclassified, the terrain correction method determination unit 14 determines the terrain correction method for the group to be no correction. If the terrain type of a group is above-water mountain, the terrain correction method determination unit 14 determines the terrain correction method for the group to be above-water mountain correction. If the type of terrain of a group is a multi-water surface slope, the terrain correction method determination unit 14 determines that the terrain correction method for the group is multi-water surface slope correction.

[0048] A water-surface mountain is a terrain where land-sea mixed passages and mountainous terrain coexist. For example, a water-surface mountain is a terrain where high islands and sea exist together. An example of a water-surface mountain is Halong Bay in Vietnam.

[0049] A multi-water slope is a terrain where land and sea intermingle and slope terrain coexist. For example, a multi-water slope is a terrain where ponds are connected in a terraced rice field pattern. An example of a multi-water slope is Jinshapudi in the Huanglong Scenic Area in China.

[0050] The following describes how to calculate the correction value K, which differs depending on the terrain correction method. Note that correction values ​​calculated using different methods may be distinguished by adding a suffix to the correction value K. For example, if the correction value for land-sea mixed passage correction is K, ｓBelow, in the land-sea mixed passage correction method, mountain correction method, hilly terrain correction method, and slope terrain correction method, a method for calculating correction values ​​based on points between the reference point and the evaluation target point will be described when points are not divided into groups, but when points are divided into groups, similar calculations are performed with the reference point as the reference point side point and the evaluation target point as the evaluation target point side point to calculate correction values ​​for the grouped points.

[0051] 9 is a flowchart showing a method for calculating the correction value K by the land-sea mixed passage correction method. The correction value calculation device 2 determines the correction coefficient P based on the position of the water surface and the total planar distance (step S141). The correction value calculation device 2 calculates the number C of points determined to be water surfaces. ｄｓ The number of all points in C ｄａ If the number of points C determined to be the water surface is less than half of the number of points C determined to be the water surface and the position of the water surface is closer to the reference point, the correction coefficient P is calculated as 0. ｄｓ The number of all points in C ｄａ If the number of points C determined to be the water surface is less than half of the number of points C determined to be the water surface and the position of the water surface is closer to the evaluation target point, the correction coefficient P is calculated as 1. ｄｓ The number of all points in C ｄａ If the number of the errors is equal to or greater than half, the correction coefficient P is calculated by the formula (9).

[0052] In formula (9), L ｃ is the distance from the reference point to the point determined to be the water surface where the cumulative distribution is at the 50th percentile. ｃ is the distance from the reference point to the midpoint among the points determined to be the water surface. ｓｔ is the distance between the points. ｓｔ ×C ｄｓ is the distance to the water surface. d is the planar distance between the reference point and the evaluation point.

[0053] The correction value calculation device 2 is L ｃ -L ｓｔ ×C ｄｓ If / 2 is 0 or less, the correction coefficient P is calculated as 0, and L ｃ -L ｓｔ ×C ｄｓ / 2 is greater than 0, and L ｃ +L ｓｔ ×C ｄｓ If / 2 is equal to or greater than d, the correction coefficient P is calculated as 1, and L ｃ -L ｓｔ ×C ｄｓ / 2 is greater than 0, and L ｃ +L ｓｔ ×C ｄｓ When / 2 is smaller than d, the correction coefficient P can be calculated by the formula (9) in the same manner as the above method.

[0054] Thereafter, the correction value calculation device 2 calculates a correction value K based on the planar distance between the reference point and the evaluation point, the ratio of the points determined to be the water surface to all points, and the correction coefficient P (step S142). ｄｓ / C ｄａ ), the planar distance d between the reference point and the evaluation point, and the correction value K for the land-sea mixed passage correction ｓ 1 is a graph showing the relationship between the correction value calculation device 2 and C ｄｓ / C ｄａ , d, K ｓ The relationship between ｄｓ / C ｄａ , d, the correction value K in the land-sea mixed passage correction ｓ Calculate.

[0055] The correction value calculation device 2 calculates the correction value K using a graph (graph indicated by b) showing the correction value when the water surface is on the reference point side, a graph (graph indicated by a) showing the correction value when the water surface is on the evaluation target point side, and a graph (hereinafter referred to as the intermediate value graph) showing the intermediate value between the graphs indicated by a and b. ｓ When the correction coefficient P is 0.5 or less, the correction value calculation device 2 calculates the correction value K using the graph indicated by b and the intermediate value graph. ｓ Specifically, the correction value calculation device 2 calculates a given C ｄｓ / C ｄａ , d, the correction value K ｂ and the correction value K shown in the intermediate value graph ｍｉｄ Based on this, the correction value K ｓ Calculate.

[0056] When the correction coefficient P is greater than 0.5, the correction value calculation device 2 calculates the correction value K using the graph indicated by a and the intermediate value graph. ｓ Specifically, the correction value calculation device 2 calculates a given C ｄｓ / C ｄａ , d, the correction value K ａ and the correction value K shown in the intermediate value graph ｍｉｄ Based on this, the correction value K is calculated using equation (11). ｓ Calculate.

[0057] Using the graph, the correction value K ｓ The correction value calculation device 2 calculates the correction value K using the calculation formula shown in the graph. ｓ Although only two graphs that change depending on the change in d are shown in FIG. 10, the correction value calculation device 2 calculates the difference between d and C in the calculation formula shown in the graph. ｄｓ / C ｄａ Using the approximate formula for the correction value K ｓ Hereinafter, the calculation method of the correction value for mountain correction, hilly land correction, and slope terrain correction will be described using graphs. The correction value calculation device 2 calculates the value of d in the calculation formula shown in the graph and d ２ , ΣH, Δh, θ ｍ The correction value K may be calculated using an approximation formula for each combination of the above.

[0058] The correction value calculation device 2 determines whether the terrain correction method is isolated mountain correction or multiple mountain correction in the mountain correction method. Isolated mountain correction is correction when there is only one mountain, and multiple mountain correction is correction when there are two or more mountains. The correction value calculation device 2 calculates all slope angles between the reference point and the ridge peaks and evaluation target points. Then, it extracts the point with the largest slope angle from among the ridge peaks and evaluation target points, and calculates all slope angles between the ridge peaks and evaluation target points using the extracted point as the new reference point. This process is repeated until the extracted point becomes the evaluation target point. If there is one extracted point other than the evaluation target point, the terrain correction method is isolated mountain correction. If there are two or more extracted points other than the evaluation target point, the terrain correction method is multiple mountain correction.

[0059] In the case of isolated mountain correction, the correction value calculation device 2 calculates the distance d between the reference point and the extracted point. １ , the distance d between the extracted point and the evaluation point ２ , and the elevation H of the extracted points excluding the evaluation target points, the isolated mountain correction value K ｉｍ Figure 11 shows the d when H = 200 m. １ , d ２ , K. ｉｍ For example, the correction value calculation device 2 calculates the value of d when H=200 m. １ , d ２ , K. ｉｍ A graph showing the relationship between １ , d ２ From the value of K ｉｍ Calculate K ｉｍ By multiplying this by a correction coefficient α = 0.07√H based on the altitude H, the isolated mountain correction value K at the desired altitude is obtained. ｉｍ can be calculated.

[0060] In the case of multiple mountain correction, the correction value calculation device 2 calculates a multiple mountain correction value K based on the sum ΣH of the elevations of the extracted points excluding the evaluation target point. ｍｍ Calculate the following equation. ｍｍ 1 is a graph showing the relationship between ΣH and K. ｍｍ Based on the graph showing the relationship between ｍｍ Calculate.

[0061] When the terrain correction method is hilly terrain correction, the correction value calculation device 2 calculates a high representative value and a low representative value from the height data of each point. The high representative value and the low representative value are quantiles, and for example, the high representative value is the 90th percentile of the height of each point, and the low representative value is the 10th percentile of the height of each point.

[0062] The correction value calculation device 2 calculates the terrain undulation height Δh, which is the difference between the high representative value and the low representative value, and calculates the terrain undulation height Δh and the hill correction value K ｈ and the terrain undulation height Δh, the hill correction value K ｈ FIG. 13 shows the relationship between the terrain undulation height Δh and the hill correction value K ｈ 10 is a graph showing the relationship between

[0063] Thereafter, if the height of the evaluation point is greater than the high representative value, that is, if the evaluation point is at the top, the correction value calculation device 2 calculates the terrain undulation height Δh and the hill fine correction value K ｈｆ and the terrain undulation height Δh, the hill fine correction value K ｈｆ Calculate the hill correction value K ｈ If the evaluation point is smaller than the low representative value, that is, if the evaluation point is in a valley, the correction value calculation device 2 adds the terrain undulation height Δh and the hill fine correction value K ｈｆ and the terrain undulation height Δh, the hill fine correction value K ｈｆ Calculate the hill correction value K ｈ FIG. 14 shows the relationship between the terrain relief height Δh and the hill fine correction value K ｈｆ 10 is a graph showing the relationship between the correction value K and the correction value calculation device 2.

[0064] When the terrain correction method is slope terrain correction, the correction value calculation device 2 calculates the planar distance d between the reference point and the evaluation target point and the slope angle θ between the reference point and the evaluation target point. ｍ and the slope correction value K ｓｐ Using the equation showing the relationship between the planar distance d between the base station and the evaluation point and the tilt angle θ between the reference point and the evaluation point, ｍ From the slope terrain correction value K ｓｐ 15 shows the planar distance d between the reference point and the evaluation point and the inclination angle θ between the reference point and the evaluation point. ｍ and the slope correction value K ｓｐ 15 is a graph showing the relationship between the tilt angle θm on the horizontal axis and the tilt angle θm in milliradians (mr).

[0065] When the terrain correction method is the above-water mountain correction, the correction value calculation device 2 calculates the correction value K. The correction value calculation device 2 calculates the correction value K by taking into account, for example, the ratio of points determined to be on the water surface to all points, the ratio of points determined to be on the water surface among points in a group determined to be a land-sea mixed passage, the maximum elevation point, the number N of islands located on a straight line from the reference point to the evaluation point, and other factors. island A correction value K is calculated based on the number of islands located on the straight line from the reference point to the evaluation point that have an altitude exceeding a predetermined value (for example, 200 m).

[0066] When the terrain correction method is multi-water surface inclination correction, the correction value calculation device 2 calculates the correction value K. For example, the correction value calculation device 2 calculates the correction value K based on the ratio of points determined to be water surfaces to all points, the ratio of points determined to be water surfaces among points in a group determined to be a land-sea mixed passage, the inclination angle θ between the reference point and the evaluation target point, and the correction value K. ｍ , the planar distance d between the reference point and the evaluation point, and the number of steps of the water surface connected in a stepped manner N stairs , the difference in water level Δh steps The correction value K is calculated based on the above.

[0067] In the embodiment described above, the terrain correction method determination device 1 determines the terrain correction method to be above-water mountain correction or multi-water surface slope correction, but this is not limited to this. When any two or more of conditions C1 to C4 are satisfied, the terrain type determination unit 13 can determine the terrain type as a specific type other than land-sea mixed passage, mountain, hilly terrain, sloping terrain, or unclassified. Furthermore, the terrain type determination unit 13 may change the order in which conditions C1 to C4 are determined depending on the type of terrain other than land-sea mixed passage, mountain, hilly terrain, sloping terrain, or unclassified.

[0068] In the embodiment described above, the terrain correction method determination device 1 determined the type of terrain in the order of conditions C1, C2, C3, and C4. For example, when the terrain is determined to be hilly or sloping terrain, it may actually be a land-sea mixed passage or mountainous. In the embodiment described above, the terrain correction method determination device 1 determines whether the type of terrain is a land-sea mixed passage or mountainous before determining whether the type of terrain is hilly or sloping terrain, thereby preventing the type of terrain from being determined to be hilly or sloping terrain when it is actually a land-sea mixed passage or mountainous.

[0069] The terrain correction method determination device 1 may determine the type of terrain by changing the order of conditions C1, C2, C3, and C4. The terrain correction method determination device 1 may determine the type of terrain by giving priority to the correction value calculated by the terrain correction method with the largest absolute value. FIG. 16 is a diagram showing the possible correction values ​​calculated by each terrain correction method. The possible correction values, in descending order of absolute value, are multiple mountain correction, hilly terrain correction, isolated mountain correction, fine hilly correction, land-sea mixed passage correction, and slope terrain correction. The terrain correction method determination device 1 may determine the type of terrain in the order of conditions C2, C3, C1, and C4. In other words, the terrain correction method determination device 1 may determine the type of terrain in the order of whether the terrain type is mountainous, hilly, land-sea mixed passage, or slope terrain.

[0070] There are other correction methods in addition to the above-described terrain correction methods: multiple mountain correction, hilly terrain correction, isolated mountain correction, fine hill correction, land-sea mixed passage correction, and slope terrain correction. The terrain correction method determination device 1 may be configured to determine a new terrain type and a new correction method. In this case, the order in which the new terrain type is determined can be set so as not to make an erroneous determination of the characteristics of each terrain, or can be set in descending order of the absolute value of the possible correction values.

[0071] One embodiment of the present invention has been described in detail above with reference to the drawings, but the specific configuration is not limited to that described above, and various design changes and the like are possible within the scope that does not deviate from the gist of the present invention.

[0072] In this embodiment, the correction value calculation device 2 uses the Okumura-Hata formula as the propagation characteristic estimation formula, but is not limited to this. For example, the correction value calculation device 2 may calculate the received power by performing correction based on the correction value K on another propagation characteristic estimation formula.

[0073] The terrain correction method determination device 1 and the correction value calculation device 2 in the above-described embodiment may be implemented in part or in whole by a computer. In this case, a program for implementing this function may be recorded on a computer-readable recording medium, and the program may be loaded into a computer system and executed. Note that the term "computer system" as used herein includes an operating system (OS) and peripheral hardware. Furthermore, the term "computer-readable recording medium" refers to portable media such as flexible disks, optical magnetic disks, ROMs, and CD-ROMs, as well as storage devices such as hard disks built into computer systems. Furthermore, the term "computer-readable recording medium" may also include media that dynamically store programs for a short period of time, such as communication lines used when transmitting programs via networks such as the Internet or telephone lines, or media that store programs for a fixed period of time, such as volatile memory within a computer system that serves as a server or client. The program may also be designed to implement some of the above-described functions, or may be capable of implementing the above-described functions in combination with programs already stored in the computer system. Furthermore, part or all of the terrain correction method determination device 1 and the correction value calculation device 2 may be realized using a programmable logic device such as an FPGA (Field Programmable Gate Array).

[0074] 1 Terrain correction method determination device, 11 Terrain information acquisition unit, 12 Terrain information analysis unit, 13 Terrain type determination unit, 14 Terrain correction method determination unit, 15 Output unit, 2 Correction value calculation device

Claims

1. A terrain correction method determination device which classifies terrain information of points between a reference point and an evaluation point according to their planar distance from the reference point, based on the planar distance between the reference point and the evaluation point, and divides the points into a plurality of groups; determines a terrain correction method for each group based on the terrain type of the group; and if the terrain type of the group includes a specific plurality of terrain types, further determines a terrain correction method for the entire group.

2. Based on information on points between the reference point and the evaluation point, determine the type of terrain for each group as either a land-sea mixed passage, mountain, hilly area, sloping terrain, or unclassified; for each group, determine the type of terrain to be the land-sea mixed passage when the ratio of the number of points determined to be water surface to the total number of points is equal to or greater than a certain level; determine the type of terrain to be mountainous when the difference in elevation between the reference point side point, which is the point with the shortest planar distance from the reference point, and the maximum elevation point, which is the highest among all of the points, is equal to or greater than a certain level, and the planar distances between the maximum elevation point and the summit of the mountain are all equal to or less than a certain level; determine the type of terrain to be hilly when the number of points that are undulating peaks among all of the points is equal to or greater than a certain level; determine the type of terrain to be sloping terrain when the maximum value of the ratio of the difference between the angle between the reference point side point and an inflection point among all of the points and the first angle, which is the angle between the reference point side point and the evaluation point side point, which is the point with the shortest planar distance between the reference point side point and the evaluation point, is equal to or greater than a certain level; The terrain correction method determination device according to claim 1 , wherein when the type of terrain is not determined to be any of the land-sea mixed passage, the mountain, the hilly area, and the sloping terrain, the type of terrain is determined to be the unclassified type.

3. The terrain correction method determination device according to claim 2, wherein when the types of terrain include a group of the land-sea mixed passage and a group of the mountains, the overall correction method is determined to be above-water mountain correction.

4. The terrain correction method determination device according to claim 2, wherein when the types of terrain include a group of the land-sea mixed passage and a group of the sloping terrain, the overall correction method is determined to be multi-water surface slope correction.

5. The terrain correction method determination device of claim 2, further comprising the steps of: determining the terrain correction method for each group as land-sea mixed passage correction when the type of the terrain is a land-sea mixed passage; determining the terrain correction method as mountain correction when the type of the terrain is not the land-sea mixed passage but is mountainous; determining the terrain correction method as hilly terrain correction when the type of the terrain is not the mountainous but is hilly; determining the terrain correction method as slope terrain correction when the type of the terrain is not the hilly but is sloping terrain; and determining no correction when the type of the terrain is not the sloping terrain.

6. A method for determining a terrain correction method, comprising: classifying terrain information of points between a reference point and an evaluation point according to their planar distance from the reference point, dividing the points into a plurality of groups, determining a terrain correction method for each group based on the terrain type of the group; and determining a terrain correction method for the entire group when the terrain type of the group includes a specific plurality of terrain types.

7. A program for causing a computer to execute the terrain correction method determining method according to claim 6.

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