A method for mapping a radar terminal satellite

Abstract

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

Description

Technical Field

[0001] This invention belongs to the field of satellite map drawing methods, and specifically relates to a method for drawing satellite maps for radar terminals. Background Technology

[0002] In the development of anti-clutter radar, in order to improve the probability of target detection, the false alarm rate is often relatively high, resulting in a large amount of clutter in the final detection results. Since traditional large radar maps only have boundary lines and the boundary range is relatively large, for anti-clutter radar with an effective range of only a few kilometers or tens of kilometers and an altitude of less than one kilometer, it is impossible to accurately provide the specific geographical information of the clutter location in the complex surrounding environment. Therefore, in order to facilitate the analysis of clutter characteristics during the development of anti-clutter radar, the radar final display interface needs to display the surrounding geographical environment. Satellite maps can clearly mark the surrounding buildings, mountains, roads, and other environmental features, which facilitates the analysis of echo data characteristics by the radar. Summary of the Invention

[0003] To address the shortcomings of the prior art, this invention employs a series of operations, such as stitching, cropping, and scaling, of map tile data following the Mercator projection rules to obtain a map image that can be displayed on the radar terminal's display interface.

[0004] The technical solution of this invention is: a method for drawing satellite maps of a radar terminal, characterized by comprising the following steps:

[0005] Step 1: The radar uses positioning equipment to locate itself. When the radar terminal performs display and control operations, it obtains the latitude and longitude of the radar station center, as well as the range and screen size of the radar terminal display interface.

[0006] Step 2: Confirm the pixel-to-distance scale by checking the range and screen size of the radar terminal display interface. Select the appropriate offline map tile level by comparing the interface scale MPD (meter per pixel) with the fixed scale GSD (Ground Sampling Distance) of each map tile level, and access the corresponding satellite map resource data package through the configuration file.

[0007] Step 3: Confirm the latitude and longitude of the center point of the radar terminal target display interface by using the ratio of pixels to distance and the latitude and longitude of the radar station center;

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

[0009] Step 5: Using the range of the radar terminal target display interface and the fixed scale of different levels of map tiles, obtain the satellite map tile resources required for the entire interface. Stitch the obtained satellite map tile resources in sequence, and then crop and scale the stitched image resources accordingly to finally obtain image resources that can be displayed on the radar terminal.

[0010] The beneficial effects of this invention are: Testing shows that the data transmission time during the entire process is extremely short, generally less than 0.1 milliseconds, and there is no significant change compared to before modularization. This invention is applicable to the modification of existing anti-radar terminals and also to the design of new anti-radar terminals. Attached Figure Description

[0011] Figure 1 This is a flowchart of the present invention.

[0012] Figure 2 This is a dynamic configuration file diagram for offline maps.

[0013] Figure 3 Radar terminal station center latitude and longitude configuration map

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

[0015] Figure 5 This is a display effect diagram for the radar terminal. Detailed Implementation

[0016] Definitions:

[0017] Satellite map data packets: The carrier of satellite map data packets is satellite map tile data. For a world map projected as a plane by the Mercator projection, at different map resolutions (the pixel size of the entire world map), the world map is divided into map units of 256×256 pixels by a segmentation method. Each map unit is called a map tile, and its characteristics are:

[0018] a. It has a unique tile level and tile coordinate row and column number;

[0019] b. Each tile has a resolution of 256×256;

[0020] c. A certain level of map tiles is composed of four tiles cut from each of the lower-level tiles, forming a tile pyramid, generally ranging from 0 to 18 levels, with level 0 being a complete 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 (unit: meter, taking the width of the radar terminal display interface as the display range) and 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, generally 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 image is required, a larger value can be taken for f, which is generally applicable to radar terminals with a smaller detection range. A smaller value can be taken for f, which is generally applicable to radar terminals with a larger detection range. f can be modified through a configuration file to select the appropriate offline map tile level and access 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's display screen is the radar station's center point. However, the center point of the radar terminal's target display screen may be offset. Therefore, it is necessary to calculate the latitude and longitude of the display screen's center point using the radar station's center point's coordinates. Using the pixel-to-distance scale (MPD), the radar station's center coordinates (Radar(x1,y1), the screen center coordinates (Center(x2,y2), and the radar station's center coordinates (lon1,lat1), the latitude and longitude (lon2,lat2) of the radar terminal's target display screen's center point are determined. The calculation formula is as follows:

[0030]

[0031] Step 4: Access the database of offline satellite map tile resources. Using the latitude and longitude of the center point of the radar terminal's target display interface, calculate the row and column number of the tile index where the center point is located through the conversion relationship between the Mercator projection's mid-latitude and longitude and the satellite map index. Then, retrieve the map tile containing the radar terminal's display center point from the database, such as... Figure 4 The tile shown requires a layer, row number, and column number as an index. The layer is obtained in step two, and the row number is confirmed through longitude. The conversion formula is as follows:

[0032]

[0033] Column numbers are determined by latitude, and the conversion formula is as follows:

[0034]

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

[0036] Step 5: Using the radar terminal target display interface's range and the fixed scale of different map tile levels, obtain the satellite map tile resources required for the entire interface. Based on the central tile, and according to the display area's range and tile scale (the tile scale is a fixed scale GSD inherent to the map resources), simply calculate the required number of tiles. The specific calculation formula is as follows:

[0037]

[0038] `rng_width` represents the horizontal range of the screen display, `rng_high` represents the vertical range, `size_width` is the width of a single tile, `size_high` is the height of a tile, `row_num` is the required number of tile rows, and `col_num` is the required number of tile columns. The row and column numbers of the horizontal and vertical tiles are then obtained directly according to an increasing / decreasing pattern. The acquired satellite map tile resources are stitched together sequentially. The stitched map image uses a `QImage` class object as the storage medium, and the stitched image is cropped according to the range and scaled according to the screen size of the radar terminal display area. The image is then transmitted using a `QImage` class object, and finally, the radar terminal receives the image resources for display. Figure 5 The circles in the image represent the distance scale coils for displaying the target, the straight lines represent the azimuth scale lines, the cone shape in the center represents the antenna scan lines, and the background is the final map image displayed.

[0039] In this invention, map resources need to be downloaded offline from the Internet in advance. Satellite map tiles are of a fixed size. After stitching, the original fixed scale GSD needs to be scaled to the scale MPD of the radar terminal display interface, which makes it easier to display map images.

[0040] The MBTiles specification used in this invention improves disk utilization by storing offline map resources. Offline map resources also eliminate the need for an internet connection for map creation, which is beneficial for meeting the requirements of domestic radar terminal production and security. Furthermore, it can be customized according to the location where the radar performs its mission. High-level map data packages only need to select a small area of ​​the map, which is more conducive to data package storage.

[0041] This invention only requires calculating the row and column numbers of the tile at the center position once. The other required tiles can be obtained directly by subtracting the row number from the left and adding the column number from the top and adding the column number from the bottom, saving a lot of calculation time.

[0042] The output of this invention uses the QImage class in Qt as the carrier for storing and transmitting image data. The QImage class uses a contiguous memory space that varies with the size of the stored information, provided by the Qt standard library. Images use this class as the storage carrier, and operations such as cropping and scaling can be performed directly on the images. This standard library can be used on any operating system. Regardless of the operating system the radar terminal needs to run on, as long as the system supports the Qt software development platform, this requirement can be met through the QImage class.

[0043] Ideally, each trigger of step one in this invention should trigger a series of actions from step two to step five, ensuring that map data can be updated in real time when functions such as eccentricity, zooming, and roaming are performed on the radar terminal display interface. However, the interface display updates independently to prevent frequent triggering of step two and map update lag.

[0044] This invention is modular, using a combination of UDP Socket communication and the QImage class to achieve local communication between the map loading module and the radar terminal. This allows the two modules to be independent yet flexibly and quickly exchange data, achieving the goal of modularizing map functionality. The two inter-process communication methods chosen in this invention are universally applicable across multiple platforms and systems, offering strong compatibility and resistance to abnormal conditions (such as memory overflows) caused by other programs. Testing shows that the data transmission time during the entire process is extremely short, generally less than 0.1 milliseconds, with no significant change compared to before modularization. This invention is applicable to the modification of existing anti-radar terminals and also to the design of new anti-radar terminals.

Claims

1. A method of mapping a radar terminal satellite map, characterized by: The method comprises the following steps: Step 1: the radar is positioned by a positioning device to obtain the longitude and latitude of the radar station center and the range and screen size of the radar terminal display interface; Step 2: the scale of pixels to distance MPD is confirmed through the range and screen size of the radar terminal display interface, the fixed scale GSD of each level of the map tile is selected through the scale MPD of the interface and the fixed scale GSD of each level of the map tile, the satellite map resource data packet of the corresponding level is accessed through the configuration file; The specific process of selecting the offline map tile level is as follows: i is the current selected level, firstly, it is judged whether i is greater than Min, if yes, the process continues, otherwise, level = Min, then it is judged whether MPD > GSD[i] is established, if not, i is decreased, if yes, it is judged whether MPD*2 < f*GSD[i] + GSD[i+1] is established, if not, level = i, if yes, if i+1 > Max, then level = i, otherwise, level = i+1; f is a weight coefficient; Step 3: the longitude and latitude of the center point of the radar terminal target display interface are confirmed through the scale relationship of pixels to distance and the longitude and latitude of the radar station center; The calculation formula is as follows: Wherein, the radar station center coordinate Radar(x1, y1), the screen center coordinate Center(x2, y2), the longitude and latitude of the radar station center (lon1, lat1), the longitude and latitude of the center point of the radar terminal target display interface (lon2, lat2); Step 4: the database of the offline satellite map tile resource is accessed, the tile index where the center point is located is calculated through the conversion relationship between the central longitude and latitude of the Mercator projection and the satellite map index by using the longitude and latitude of the center point of the radar terminal target display interface, and the map tile where the center point is located is obtained from the database; The row number conversion formula is as follows: The column number conversion formula is as follows: Wherein, lon is the longitude, lat is the latitude, level is the tile map level, row is the row number, and col is the column number; Step 5: the satellite map tile resource required by the entire interface is obtained through the range of the radar terminal target display interface and the fixed scale of different levels of the map tile, the center tile is taken as the basis, the required tile quantity is calculated according to the range of the display area and the scale of the tile, and the specific calculation formula is as follows: The specific calculation formula is as follows: The weight coefficient f is between 1 and 2.

2. The method of claim 1, wherein: The pixel-to-distance scale MPD is calculated as:

3. The method of claim 1, wherein: ​ 4. The method of claim 1, wherein: The map picture spliced in sequence from the satellite map tile resources uses a QImage class object as a storage carrier, the spliced picture is cropped according to the range, is scaled according to the screen size of the radar terminal display area, and the picture is transmitted using the QImage class object.

5. The method of claim 1, wherein: The map resource in step two uses the MBTiles specification as a data storage rule.

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