Radar terminal satellite map drawing method

Abstract

The invention belongs to the field of satellite map drawing methods, and particularly relates to a radar terminal satellite map drawing method. The method comprises the following steps: positioning a radar through a positioning device to obtain the longitude and latitude of a radar station center and the range and screen size of a radar terminal display interface; accessing the satellite map resource data packet of the corresponding level by the configuration file; confirming the longitude and latitude of the center point of the target display interface of the radar terminal; calculating the index of the tile where the center point is located, and obtaining the map tile where the center point is located from the database; and displaying according to the measuring range of the display area and the proportional scale of the tile. According to the invention, the surrounding environment of the radar target can be timely and effectively displayed, and further position confirmation of the radar target and acquisition of other information are facilitated.

Description

Technical Field

[0001] The invention belongs to the field of satellite map drawing methods, and particularly relates to a radar terminal satellite map drawing method. Background Art

[0002] In the process of developing anti-no-seepage radar, in order to improve the probability of target detection, the false alarm rate is often high, resulting in a large amount of clutter in the final detection results. Since the map of traditional large radars only has boundary lines, and the boundary range is large, for anti-no-seepage radars with a range of only a few kilometers or more than ten kilometers and an altitude of less than one kilometer, the surrounding environment is relatively complex, and it is impossible to accurately give the specific geographical information of the location where the clutter appears. Therefore, in order to facilitate the analysis of clutter characteristics during the development of anti-no-seepage radars, the radar final display interface needs to display the surrounding geographical environment, and satellite maps can clearly mark the surrounding buildings, mountains, roads and other environments, which is convenient for radars to analyze echo data characteristics. Summary of the invention

[0003] In view of the shortcomings of the background technology, the present invention performs a series of operations such as splicing, cropping, and scaling on map tile data of Mercator projection rules to obtain a map image that can be displayed on the display interface of the radar terminal.

[0004] The technical solution of the present invention is: a method for drawing a radar terminal satellite map, characterized in that it comprises the following steps:

[0005] Step 1: The radar is positioned through the positioning device. When the radar terminal is operated for display and control, the longitude and latitude of the radar station center and the range and screen size of the radar terminal display interface are obtained;

[0006] Step 2: Confirm the scale of pixels and distances through the range and screen size of the radar terminal display interface, select the appropriate offline map tile level through the interface scale MPD (meter per pixel) and the fixed scale GSD (ground sampling distance) of each level of map tiles, and access the satellite map resource data package of the corresponding level through the configuration file;

[0007] Step 3: confirm the longitude and latitude of the center point of the target display interface of the radar terminal through the proportional relationship between pixels and distance and the longitude and latitude of the center of the radar station;

[0008] Step 4: Access the database of offline satellite map tile resources, use the longitude and latitude of the center point of the target display interface of the radar terminal, calculate the tile index of the center point through the conversion relationship between the longitude and latitude of the Mercator projection and the satellite map index, and obtain the map tile of the center point from the database;

[0009] Step 5: Obtain the satellite map tile resources required for the entire interface through the range of the radar terminal target display interface and the fixed scales of different levels of map tiles, stitch the acquired satellite map tile resources in sequence, and crop and scale the stitched image resources accordingly, and finally obtain image resources that meet the requirements of the radar terminal for display.

[0010] The beneficial effect of the present invention is that after testing, the time spent on data transmission in the whole process is very short, generally less than 0.1 milliseconds, and there is no significant change before modularization. The present invention is suitable for the terminal transformation of the current anti-no radar, and is also suitable for the terminal design of a new anti-no radar. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a flow chart of the present invention.

[0012] Figure 2 Dynamically configure file maps for offline maps.

[0013] Figure 3 Radar terminal station centroid longitude and latitude configuration diagram

[0014] Figure 4 Store database tables for offline maps.

[0015] Figure 5 Displays the effect image for the radar terminal. DETAILED DESCRIPTION

[0016] Glossary:

[0017] Satellite map data package: The carrier of satellite map data package is satellite map tile data. For the world map which is a plane after Mercator projection, the world map is divided into map units of 256×256 pixels by cutting at different map resolutions (pixel size of the entire world map). Each map unit is called a map tile, which has the following characteristics:

[0018] a. Has a unique tile level (Level) and tile coordinate row and column number (row, column);

[0019] b. The resolution of each tile is 256×256;

[0020] c. The tiles of a certain tile level map are composed of 4 tiles cut from the tiles of the lower level, forming a tile pyramid, generally 0-18 levels, with level 0 being a whole world map;

[0021] d. The higher the tile level, the more tiles make up the world map, and the more detailed the map can be displayed.

[0022] The tiles are stored using the MBTiles specification and accessed via an SQLite database, which can reduce the resource space occupied by satellite maps. As Figure 4 shown, zoom_level is the tile level, tile_column is the row number, tile_row is the column number, and tile_data is the corresponding satellite map image data.

[0023] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0024] As Figure 1 shown, the specific implementation steps of the present invention are as follows:

[0025] Step 1: The radar is positioned through a positioning device. As Figure 2 shown, set the longitude and latitude of the radar station center. When performing display and control operations on the radar terminal, obtain the longitude and latitude of the center of the display area of the radar terminal and the range rng (in meters, taking the width of the radar terminal display interface as the display range) and the screen size (width, high) of the radar terminal display interface;

[0026] Step 2: Confirm the scale MPD of pixels to distance through the range and screen size of the radar terminal display interface. The calculation formula is:

[0027]

[0028] After obtaining the scale MPD (meter per pixel) of the interface and the fixed scale GSD (ground sampling distance) of each level of the map tiles, as Figure 3 shown, calculate the satellite map tile level. Here, i is the currently selected level, usually initialized to the maximum level Max of the data packet. First, determine whether i is greater than Min. If it is greater than Min, continue; otherwise, level = Min. Then, determine whether MPD > GSD[i] holds. If it does not hold, i is decremented. If it holds, continue to determine whether MPD * 2 < f * GSD[i] + GSD[i + 1] holds. If it does not hold, level = i. When it holds, if i + 1 > Max, then level = i; otherwise, level = i + 1. Here, f is a user-defined weight, generally between 1 and 2, and can be selected according to the user's visual experience. If a clearer map画面 is required, a larger value can be taken for f, which is generally applicable to radar terminals with a smaller detection range. If a smaller value is taken for f, it is generally applicable to radar terminals with a larger detection range. f can be modified through a configuration file, thereby selecting the appropriate offline map tile level and accessing the satellite map resource data packet of the corresponding level through the configuration file. In this step, the map resources use the MBTiles specification as the data storage rule, and the generated offline map data packet has strong portability and can effectively improve the disk space utilization rate.

[0029] Step 3: Normally, the center of the radar terminal display interface is the center of the radar station. However, the center of the radar terminal target display interface may be offset. In this case, the latitude and longitude of the center of the display interface must be calculated using the latitude and longitude of the center of the radar station. The latitude and longitude (lon2, lat2) of the center of the radar terminal target display interface can be determined using the pixel-to-distance scale MPD, the radar station center coordinates Radar (x1, y1), the screen center coordinates Center (x2, y2), and the longitude and latitude (lon1, lat1). The calculation formula is:

[0030]

[0031] Step 4: Access the database of offline satellite map tile resources, use the longitude and latitude of the center point of the radar terminal target display interface, calculate the tile index row and column number of the center point through the conversion relationship between the longitude and latitude of the Mercator projection and the satellite map index, and obtain the map tile where the radar terminal displays the center point from the database, such as Figure 4 The tiles shown require level, row number, column number, etc. as indexes. The level is obtained by step 2, and the row number is confirmed by longitude. The conversion formula is:

[0032]

[0033] The column number is confirmed by latitude, and the conversion formula is:

[0034]

[0035] Where lon is longitude, lat is latitude, level is the tile map level, row is the integer downward as the row number, and col is the integer downward as the column number;

[0036] Step 5: Obtain the satellite map tile resources required for the entire interface through the range of the radar terminal target display interface and the fixed scales of different levels of map tiles. Based on the center tile, according to the range of the display area and the scale of the tile, the scale of the tile is the fixed scale GSD of the map resource. You only need to calculate the number of tiles required. The specific calculation formula is:

[0037]

[0038] rng_width is the horizontal scale displayed on the screen, rng_high is the vertical scale displayed on the screen, size_width is the width of a single tile, size_high is the height of the tile, row_num is the required number of tile rows, clo_num is the required number of tile columns, and then the row and column numbers of the horizontal and vertical tiles are directly obtained according to the increasing and decreasing rules. The obtained satellite map tile resources are spliced ​​in sequence, and the spliced ​​map image uses the QImage class object as the storage carrier, and the spliced ​​image is cropped accordingly according to the scale, scaled according to the screen size of the radar terminal display area, and the image is transmitted using the QImage class object. Finally, the radar terminal obtains the image resource for display as shown below: Figure 5 The circle in the figure is the distance scale coil that displays the target, the straight line is the azimuth scale line, the cone shape in the center is the antenna scanning line, and the background is the final map image displayed.

[0039] In the present invention, the map resources need to be downloaded from the Internet in advance as offline resources. The satellite map tiles are of a fixed size. After splicing, the original fixed scale GSD needs to be scaled to the scale MPD of the radar terminal display interface, which is more convenient for map image display.

[0040] The MBTiles specification used in the present invention to store offline map resources improves disk utilization. Offline map resources make it unnecessary to connect to the Internet for drawing maps, which is conducive to meeting the localization requirements and confidentiality requirements of radar terminals. In addition, the radar can be specially customized according to the location where the radar performs the task. High-level map data packets only need to select maps within a small range, which is more conducive to the storage of data packets.

[0041] The present invention only needs to calculate the row and column numbers of the tiles at the center position once, and other required tiles can be directly obtained by subtracting the row numbers from the left and adding them from the right, and subtracting the column numbers from the top and adding them from the bottom, thus saving a lot of calculation time.

[0042] The output of the present invention uses the QImage class in QT as a carrier for storing and transmitting image data. The QImage class uses a continuous memory space that changes with the size of the stored information, which is provided by the Qt standard library. The picture uses this class as a storage carrier, and operations such as cropping and scaling can be performed directly on the picture. This standard library can be used under any operating system. No matter what operating system the radar terminal needs to run under, as long as the system can support the Qt software development platform, this requirement can be achieved through the QImage class.

[0043] It is best that each triggering of step 1 of the present invention will trigger a series of actions such as steps 2 to 5 to ensure that the map data can be updated in real time when the radar terminal display interface performs functions such as eccentricity, zooming, and roaming, but the interface display is updated independently to prevent frequent triggering of step 2 and map update jams.

[0044] The present invention can be modularized, and the local communication between the map loading module and the radar terminal is realized by combining UDP Socket communication with the QImage class, so that the two are not only two independent modules, but also can flexibly and quickly exchange data, so as to achieve the purpose of modularization of map functions. The two inter-process communication modes selected by the present invention are both universal for multiple platforms and multiple systems, have strong compatibility and are not easily affected by abnormal conditions (such as memory overflow) generated by other programs. After testing, the time spent on data transmission in the whole process is very short, generally less than 0.1 milliseconds, and there is no obvious change before modularization. The present invention is suitable for the terminal transformation of the current anti-radar, and is also suitable for the terminal design of new anti-radar.

Claims

1. A method for drawing a radar terminal satellite map, characterized in that: It includes the following steps: Step 1: The radar is positioned through a positioning device to obtain the longitude and latitude of the radar station center, as well as the range and screen size of the radar terminal display interface; Step 2: Based on the range and screen size of the radar terminal display interface, confirm the scale MPD of pixels to distance. Through the scale MPD of the interface and the fixed scale GSD of each level of the map tiles, select the offline map tile level, and access the satellite map resource data packet of the corresponding level through the configuration file; The specific process of selecting the offline map tile level is as follows: Let i be the currently selected level. First, determine whether i is greater than Min. If it is greater than Min, continue; otherwise, level = Min. Then, determine whether MPD > GSD[i] holds. If it does not hold, i is decremented. If it holds, continue to determine whether MPD * 2 < f * GSD[i] + GSD[i + 1] holds. If it does not hold, level = i. When it holds, if i + 1 > Max, then level = i; Otherwise, level = i + 1; f is the weight coefficient; Step 3: Confirm the longitude and latitude of the center point of the radar terminal target display interface through the proportional relationship between pixels and distance and the longitude and latitude of the radar station center; The calculation formula is where the radar station center coordinates are Radar(x1, y1), the screen center coordinates are Center(x2, y2), the longitude and latitude of the radar station center are (lon1, lat1), and the longitude and latitude of the center point of the radar terminal target display interface are (lon2, lat2); Step 4: Access the database of the offline satellite map tile resources. Using the longitude and latitude of the center point of the radar terminal target display interface, calculate the tile index where the center point is located through the conversion relationship between the central longitude and latitude of the Mercator projection and the satellite map index, and obtain the map tile where the center point is located from the database; The formula for converting the row number is: The formula for converting the column number is: where lon is the longitude, lat is the latitude, level is the tile map level, row is the row number obtained by rounding down, and col is the column number obtained by rounding down; Step 5: Through the range of the radar terminal target display interface and the fixed scales of different levels of the map tiles, obtain the satellite map tile resources required for the entire interface. Based on the central tile, and then according to the range of the display area and the scale of the tiles, the scale of the tiles is the fixed scale GSD provided by the map resources, calculate the required number of tiles. The specific calculation formula is: rng_width is the horizontal range of the screen display, rng_high is the vertical range of the screen display, size_width is the width of a single tile, size_high is the height of the tile, row_num is the number of required tile rows, clo_num is the number of required tile columns. Obtain the row and column numbers of the horizontal and vertical tiles directly according to the increasing and decreasing rules, and splice the obtained satellite map tile resources in sequence.

2. The method for drawing a radar terminal satellite map according to claim 1, characterized in that: The MPD calculation formula for the pixel-to-distance ratio is:

3. The method for drawing a radar terminal satellite map according to claim 1, characterized in that: The weight coefficient f is between 1 and 2.

4. The method for drawing a radar terminal satellite map according to claim 1, characterized in that: The map image after the satellite map tile resources are stitched together in sequence uses the QImage class object as the storage carrier. The stitched image is cropped accordingly according to the range, scaled according to the screen size of the radar terminal display area, and transmitted using the QImage class object.

5. The method for drawing a radar terminal satellite map according to claim 1, characterized in that: The map resources in step 2 use the MBTiles specification as the data storage rule.

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