A rapid topographic mapping method based on GPS

Abstract

The present application relates to topographic mapping technical field, specifically to a kind of topographic mapping method based on GPS, comprising the following steps: using flight equipment with GPS module carries aerial camera along preset flight path, records flight path information, and periodically takes aerial image;Aerial image is associated with aerial camera GPS coordinate;Read aerial image and establish ground object model, obtain ground object model set;According to aerial image and corresponding aerial camera GPS coordinate, obtain the three-dimensional coordinate information of each ground object model in ground object model set;According to the three-dimensional coordinate information of ground object model, establish topographic model, and the topographic model is used as topographic mapping result.The beneficial technical effects of the present application: aerial image is obtained by aerial photography, and the acquisition efficiency of aerial image is extremely high, aerial image is associated with GPS coordinate information, and the establishment of ground object model is used to realize the establishment of topographic model, so as to quickly complete the mapping of terrain.

Description

Technical Field

[0001] This invention relates to the field of topographic mapping technology, and specifically to a GPS-based rapid topographic mapping method. Background Technology

[0002] With the development of big data and artificial intelligence technologies, highly intelligent applications based on big data have begun to gain attention across various industries and have experienced rapid development. Examples include road planning, power grid optimization, and intelligent fire monitoring. Leveraging big data technology, these applications can utilize vast amounts of surveying data to produce more comprehensive and scientific planning results, ultimately achieving significant social benefits. All these applications require the support of topographic surveying data. However, existing surveying methods for topographic surveying are inefficient and cannot meet the ever-increasing demand for topographic data. Therefore, it is necessary to research new topographic surveying technologies. Aerial photography refers to taking pictures of the Earth's surface from the air to obtain a bird's-eye view, also known as an aerial photograph. Aerial cameras can be controlled by photographers, or they can be used automatically or remotely. While aerial photography can quickly obtain images of the surface of a region, it cannot obtain topographic surveying results.

[0003] Existing technology discloses a method for measuring cadastral topography in surveying engineering, including: preliminary data preparation, working map preparation, development of survey work plan, review of cadastral data for the work area, collection of current status maps of the land to be measured, and analysis of basic engineering geological elements and adverse and special geological conditions. This technical solution uses drones to acquire aerial photographs of the cadastral topography to be surveyed, processes them, marks them at designated points, and then calculates distances using distance calculation formulas, eliminating the need for manual on-site surveying of raw data. While this technical solution can obtain topographic distance data, it cannot build a topographic model and therefore cannot meet the relevant topographic data requirements. Summary of the Invention

[0004] The technical problem this invention aims to solve is the current lack of a rapid method for obtaining topographic mapping data. This invention proposes a GPS-based rapid topographic mapping method that can quickly establish topographic data using aerial photography equipment.

[0005] To solve the above technical problems, the present invention adopts the following technical solution: a GPS-based rapid terrain mapping method, comprising the following steps:

[0006] The flight equipment with GPS module carries a drone camera and flies along a preset route to record route information and periodically take aerial images.

[0007] Associate aerial images with the GPS coordinates of the aerial camera;

[0008] Read aerial images and build ground landmark models to obtain a set of ground landmark models;

[0009] Based on the aerial images and the corresponding GPS coordinates of the aerial cameras, obtain the three-dimensional coordinate information of each ground object model in the ground object model set;

[0010] A terrain model is established based on the three-dimensional coordinate information of the ground landmark model, and the terrain model serves as the terrain mapping result.

[0011] Preferably, the route information includes multiple waypoints, the coordinates of the waypoints, the timestamp of arrival at the waypoints, and the flight speed at the waypoints. The multiple waypoints are connected in sequence to form a preset route, and the aerial images are associated with the shooting timestamp and the GPS coordinates of the flight equipment at the time of shooting.

[0012] Preferred methods for associating aerial images with the GPS coordinates of the aerial camera include:

[0013] The relative coordinates of the aerial camera and the positioning point of the flight equipment are obtained. The GPS coordinates of the flight equipment are then superimposed on the relative coordinates to obtain the GPS coordinates of the aerial camera.

[0014] Preferred methods for establishing ground landmark models include:

[0015] Create a region template;

[0016] Use region templates to identify regions in aerial images;

[0017] Create a ground landmark model for each region.

[0018] As a preferred method, the methods for establishing ground landmark models in each region include:

[0019] Establish ground landmark model elements for each region;

[0020] Extract color blocks from each aerial image and obtain the boundary lines of the color blocks;

[0021] Read two aerial images in which the boundary line appears, and calculate the three-dimensional coordinates of at least two points on the boundary line;

[0022] Preserve the boundary lines that extend vertically or horizontally to obtain the preserved boundary lines in each aerial image;

[0023] Merge identical preserved boundary lines from different aerial images, and group the merged preserved boundary lines according to region;

[0024] After rotating and scaling the ground landmark model elements of the corresponding area, they are matched with the preserved boundary lines. If the match is successful, the ground landmark model is established based on the orientation and size of the rotated and scaled ground landmark model elements.

[0025] Preferred methods for merging and preserving boundary lines include:

[0026] Merge collinear boundary lines;

[0027] Merge mutually parallel boundary lines that are less than a preset threshold;

[0028] Merge intersecting boundary lines with an angle less than a preset threshold.

[0029] Preferably, the area templates include road area templates, building area templates, plaza area templates, and green area templates. The road area templates include road color ranges and road surface feature matching sets. The road surface feature sets include pedestrian crossing matching templates, traffic light matching templates, and road shape matching templates. Color regions that conform to the road color ranges are extracted from the aerial image to obtain the envelope region of the color regions. Within the envelope region, the road surface feature matching set is used to match local regions of the envelope region. If a local region matches any matching template in the road surface feature matching set, the envelope region is determined to be a road region.

[0030] The plaza area template includes a plaza shape matching template. Color blocks are extracted from the aerial image, and color blocks with pixel areas smaller than a preset threshold are removed to obtain the envelope of the remaining color blocks. If the envelope can be matched with the plaza shape matching template after rotation and perspective distortion, the area enclosed by the envelope is determined to be the plaza area. The green area template records the color range of the green area. Color areas in the aerial image that match the color range of the green area are extracted, and areas with pixel areas smaller than a preset threshold are removed. The remaining area is taken as the green area. The building area template includes several building outline matching templates. Color block edges are extracted from the aerial image. The building outline matching template is rotated, scaled, and perspective distorted, and then matched with the color block edges. If the match is successful, the color block edges are determined to be building edges. A polygonal area composed of polylines is used to enclose all building edges, and the polygonal area is regarded as the building area.

[0031] Preferred methods for establishing ground landmark model elements include:

[0032] A road model element is established, which includes the road cross-sectional shape and the extension curve. After the extension curve is matched with the center line of the road area in the aerial image, the road cross-section extends along the extension curve to form a road model.

[0033] A columnar building model element is established, which includes several preset base shapes and column heights. The base shape matches the base shape of the building in the aerial image, and the column height matches the height of the building in the aerial image. The base shape extends along the vertical line to reach the column height, thus forming a columnar building model.

[0034] An irregular building model element is established, which includes several envelope curves. The envelope curves are located on a vertical plane. After the several envelope curves match the vertical cross-sectional shape of the irregular building, an irregular building model is formed.

[0035] A square model element is established, which includes a polygonal outline. After the polygonal outline is matched with the square area in the aerial image, it is stretched to a preset thickness along the vertical direction to form a square model.

[0036] Preferred methods for obtaining the three-dimensional coordinate information of ground landmark models include:

[0037] Select the landmark points of the ground landmark model;

[0038] Read two aerial images that both show the same landmark point;

[0039] The three-dimensional coordinates of the object point are calculated based on the pixel position of the object point in the two aerial images and the camera coordinates corresponding to the aerial images.

[0040] The three-dimensional coordinate information of the ground object model is obtained from the object points.

[0041] Preferred methods for calculating the three-dimensional coordinates of the object point include:

[0042] Establish the field of view of the aerial camera on the sea level, denoted as the reference field of view, and obtain the relative coordinates of each point within the reference field of view relative to the aerial camera;

[0043] Obtain the pixel position of the target point in the aerial image, and then the coordinates of the corresponding mapped point on the reference view area;

[0044] The object point lies on the line connecting the camera coordinates and the mapping point;

[0045] Two aerial images will yield the coordinates of the two lines connecting the target point, and the coordinates of the intersection of the two lines will be the three-dimensional coordinates of the target point.

[0046] As a preferred method, the methods for selecting landmark points of the ground landmark model include:

[0047] Mark the boundary of the ground object model element, and set a number of preset object points on the object boundary;

[0048] Based on the orientation of the boundary matching in the meta-region of the ground object model, the object boundary and preset object point in the visible state are obtained, and the preset object point in the visible state is used as the selected object point on the ground object model.

[0049] Obtain the boundary of the target point in the aerial image;

[0050] Two navigation points are selected on the flight path. The distance between the two navigation points is less than a preset upper threshold and greater than a preset lower threshold, so that aerial images from two angles can be selected to find the boundary corresponding to the object boundary in both aerial images.

[0051] The aerial images corresponding to the two angles are selected as the two aerial images.

[0052] Preferably, the method for annotating the boundary of the ground landmark model element includes:

[0053] Label all vertices of the ground object model element, and the lines connecting the vertices serve as the boundaries of the ground object model.

[0054] As a preferred method, the method for obtaining the three-dimensional coordinate information of the ground landmark model based on the three-dimensional coordinates of the landmark points includes:

[0055] Substitute the three-dimensional coordinates of the landmark points into the rotated and scaled ground landmark model to obtain the endpoint coordinate information of the landmark boundary of the ground landmark model. The endpoint coordinate information of all landmark boundaries constitutes the three-dimensional coordinate information of the ground landmark model.

[0056] The beneficial technical effects of this invention include: obtaining aerial images through aerial photography, which has extremely high acquisition efficiency; the aerial images are associated with GPS coordinate information; and the establishment of a terrain model by using a ground landmark model, thereby quickly completing terrain mapping; the terrain model can be established through the ground landmark model, facilitating the use of various applications based on the terrain model; and the efficiency and accuracy of ground landmark model establishment can be improved by dividing the area before establishing the ground landmark model.

[0057] Other features and advantages of the present invention will be disclosed in detail in the following detailed description and accompanying drawings. Attached Figure Description

[0058] The invention will be further described below with reference to the accompanying drawings:

[0059] Figure 1 This is a schematic diagram of the rapid terrain mapping method according to an embodiment of the present invention.

[0060] Figure 2 This is a schematic diagram of the method for establishing a ground landmark model according to an embodiment of the present invention.

[0061] Figure 3 This is a schematic diagram of the method for establishing a ground landmark model in a region according to an embodiment of the present invention.

[0062] Figure 4 This is a schematic diagram of the process for the method of preserving boundary lines in an embodiment of the present invention.

[0063] Figure 5 This is a schematic diagram of the method for establishing a ground landmark model in an embodiment of the present invention.

[0064] Figure 6 This is a schematic diagram of road area matching according to an embodiment of the present invention.

[0065] Figure 7 This is a schematic diagram of region matching in an embodiment of the present invention.

[0066] Figure 8 This is a schematic diagram of a columnar building model according to an embodiment of the present invention.

[0067] Figure 9 This is a schematic diagram of the method for obtaining three-dimensional coordinate information of a ground landmark model according to an embodiment of the present invention.

[0068] Figure 10 This is a schematic diagram of the method for calculating the three-dimensional coordinates of a landmark point according to an embodiment of the present invention.

[0069] Figure 11 This is a schematic diagram of the reference viewing area in an embodiment of the present invention.

[0070] Figure 12 This is a schematic diagram of the mapping points in an embodiment of the present invention.

[0071] Among them: 10, road area; 11, road model; 20, aerial image; 30, green area; 40, building area; 41, boundary line; 50, columnar building model element; 51, deformed columnar building model element; 60, columnar building model; 70, aerial camera; 80, reference view area; 81, mapping point. Detailed Implementation

[0072] The technical solutions of the embodiments of the present invention will be explained and described below with reference to the accompanying drawings. However, the following embodiments are only preferred embodiments of the present invention and not all of them. Other embodiments obtained by those skilled in the art based on the embodiments in the implementation methods without creative effort are all within the protection scope of the present invention.

[0073] In the following description, terms such as “inner,” “outer,” “upper,” “lower,” “left,” and “right” are used only to facilitate the description of embodiments and simplify the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0074] Before introducing the technical solution of this embodiment, the application background of this embodiment will be introduced.

[0075] Topographic surveying refers to the work of mapping topographic features. It involves determining the projection positions and elevations of ground features and terrain within a specific area onto a horizontal plane, reducing them to a certain scale, and then drawing them into a topographic map using symbols and annotations. Topographic surveying primarily employs aerial photogrammetry methods, including control surveying and detail surveying. Depending on the instruments used, detail surveying is mainly divided into plane table mapping, combined plane table and theodolite mapping, and theodolite mapping. The main purpose of topographic surveying is to ensure the timeliness of topographic maps and the updating requirements of basic geographic information data, thereby meeting the needs of urban planning, construction, and management, and better providing surveying services and support to all sectors of society. With the development of big data and artificial intelligence technologies, a large number of highly intelligent management systems are being applied in public service sectors, such as power grid planning, road construction planning, and fire dispatching. With the support of sufficient data, artificial intelligence technologies enable more scientific and efficient planning activities. These public services frequently require the use of three-dimensional topographic data of the relevant areas. Traditional topographic mapping methods are not only costly and inefficient, but also generate non-electronic data that cannot be directly applied to artificial intelligence technologies. Clearly, they cannot provide the topographic data required. Therefore, this embodiment proposes a GPS-based rapid topographic mapping method. Please refer to the appendix. Figure 1 This includes the following steps:

[0076] Step A01) Use a flight device with a GPS module to carry an aerial camera 70 to fly along a preset route, record route information, and periodically take aerial images 20.

[0077] Step A02) Associate the aerial image 20 with the GPS coordinates of the aerial camera 70;

[0078] Step A03) Read the aerial image 20 and build a ground landmark model to obtain a set of ground landmark models;

[0079] Step A04) Based on the aerial image 20 and the corresponding GPS coordinates of the aerial camera 70, obtain the three-dimensional coordinate information of each ground object model in the ground object model set;

[0080] Step A05) Establish a terrain model based on the three-dimensional coordinate information of the ground landmark model. The terrain model serves as the terrain mapping result.

[0081] The flight path information includes multiple waypoints, their coordinates, arrival timestamps, and flight speeds at each waypoint. These waypoints are connected sequentially to form a pre-defined flight path. Aerial image 20 is associated with a capture timestamp and the GPS coordinates of the flight equipment at the time of capture. This flight path information is recorded by the aircraft during flight. After all landmark models are established, a pre-defined terrain model is used to fill in the areas not covered by the landmark models, completing the modeling of the entire terrain. Any point on the blank terrain is selected, and its 3D coordinates are calculated to obtain the ground elevation. The terrain model has a pre-defined thickness; by adapting the upper surface of the terrain model to the elevation, a terrain model matching aerial image 20 is obtained.

[0082] The method for associating aerial image 20 with the GPS coordinates of aerial camera 70 includes: obtaining the relative coordinates of aerial camera 70 and the positioning point of the flight equipment; superimposing the relative coordinates on the GPS coordinates of the flight equipment to obtain the GPS coordinates of aerial camera 70. The positioning point of the aerial device is usually the positioning point of the GPS module.

[0083] Please see the appendix Figure 2 Methods for establishing ground landmark models include:

[0084] Step B01) Create a region template;

[0085] Step B02) Use region templates to identify regions in aerial image 20;

[0086] Step B03) Establish a ground landmark model for each area.

[0087] By establishing a region template and matching the region in the aerial image 20 with the region template, a landmark model can be established within the region, which can improve the efficiency and accuracy of establishing the landmark model.

[0088] The regional templates used in this embodiment include a road region 10 template, a building region 40 template, a plaza region template, and a green area 30 template. The road region 10 template includes a road color range and a road surface feature matching set. The road surface feature set includes a pedestrian crossing matching template, a traffic light matching template, and a road shape matching template. Color regions that conform to the road color range are extracted from the aerial image 20 to obtain the envelope region of the color region. Within the envelope region, the road surface feature matching set is used to match local regions of the envelope region. If a local region matches any matching template in the road surface feature matching set, the envelope region is determined to be the road region 10. The plaza region template includes a plaza shape matching template. Color blocks are extracted from the aerial image 20, and color blocks with a pixel area smaller than a preset threshold are removed. The envelope of the remaining color blocks is obtained. If the envelope can be matched with the square shape matching template after rotation and perspective deformation, the area enclosed by the envelope is determined to be the square area. The green area 30 template records the color range of the green area 30. The color areas in the aerial image 20 that match the color range of the green area 30 are extracted. Areas with pixel areas smaller than a preset threshold are removed, and the remaining area is taken as the green area 30. The building area 40 template includes several building outline matching templates. The color block edges in the aerial image 20 are extracted. The building outline matching template is rotated, scaled, and perspective deformed, and then matched with the color block edges. If the match is successful, the color block edges are determined to be building edges. All building edges are enclosed by a polygonal area formed by polylines. The polygonal area is regarded as the building area 40.

[0089] Please see the appendix Figure 3 Methods for establishing ground landmark models for each region include:

[0090] Step C01) Establish ground landmark model elements for each region;

[0091] Step C02) Extract color blocks from each aerial image 20 to obtain the boundary lines 41 of the color blocks;

[0092] Step C03) Read two aerial images 20 that both appear on the boundary line 41, and calculate the three-dimensional coordinates of at least two points on the boundary line 41;

[0093] Step C04) Retain the boundary line 41 extending in the vertical or horizontal direction to obtain the retained boundary line 41 in each aerial image 20;

[0094] Step C05) Merge the same preserved boundary lines 41 in different aerial images 20, and group the merged preserved boundary lines 41 according to region;

[0095] Step C06) After rotating and scaling the ground landmark model elements in the corresponding area, match them with the reserved boundary line 41. If the match is successful, establish the ground landmark model with the orientation and size of the rotated and scaled ground landmark model elements.

[0096] The boundary lines 41 of the color blocks are extracted from the aerial image 20. The extraction of the boundary lines 41 of the color blocks is a prior art in this field and will not be described in detail here. After obtaining the boundary lines 41, the boundary lines 41 are matched with the ground object model elements to obtain a ground object model that matches the aerial image 20.

[0097] Please see the appendix Figure 4 The method for fusing and preserving boundary lines 41 includes: step D01) fusing collinear preserved boundary lines 41; step D02) fusing mutually parallel preserved boundary lines 41 with a distance less than a preset threshold; and step D03) fusing intersecting preserved boundary lines 41 with an angle less than a preset threshold. The same boundary line 41 appears in multiple aerial images 20. When calculating the coordinate information of the boundary line 41, there may be slight differences, which could cause the same boundary line 41 to be considered as two boundary lines 41. Therefore, the method provided in this embodiment is needed to fuse the boundary lines 41.

[0098] Please see the appendix Figure 5 Methods for establishing ground landmark model elements include:

[0099] Step E01) Establish a road model 11 element. The road model 11 element includes the road cross-sectional shape and the extension curve. After the extension curve is matched with the center line of the road area 10 in the aerial image 20, the road cross-section extends along the extension curve to form the road model 11.

[0100] Step E02) Establish a columnar building model element 50. The columnar building model element 50 includes several preset base shapes and column heights. The base shape matches the building base shape in the aerial image 20, and the column height matches the building height in the aerial image 20. The base shape extends along the vertical line to reach the column height, thus forming a columnar building model 60.

[0101] Step E03) Establish irregular building model elements. The irregular building model elements include several envelope curves. The envelope curves are located on the vertical plane. After several envelope curves match the vertical cross-sectional shape of the irregular building, they form an irregular building model.

[0102] Step E04) Establish a square model element. The square model element includes a polygonal outline. After the polygonal outline is matched with the square area in the aerial image 20, it is stretched with a preset thickness along the vertical direction to form a square model.

[0103] Please see the appendix Figure 6By extracting a preset road color range from the aerial image 20, the shape of the road can be obtained. Then, by stretching along a preset extension thickness, a three-dimensional road model 11 can be obtained. The preset extension thickness is a constant value, selected according to local road construction standards or the average road thickness within the region. Please refer to the appendix. Figure 7 This is a schematic diagram of the region division results. By dividing the aerial image 20 into multiple regions, the types of ground attachments in each region are reduced. This allows for the rapid creation of landmark models and improves the accuracy of the landmark model creation.

[0104] Please see the appendix Figure 8 This refers to the process of matching the object model element with the aerial image 20. The boundaries of color patches are extracted from the aerial image 20. Boundary extraction of color patches is a prior art technique and will not be elaborated upon here. After obtaining the boundaries, the corresponding object model element is selected. Figure 7 Select columnar building model element 50. Modify the bottom shape of columnar building model element 50 to match the boundary, and then scale and rotate columnar building model element 50 to obtain deformed columnar building model element 51. Then align the deformed columnar building model element 51 with the boundary position in aerial image 20 to obtain columnar building model 60.

[0105] Please see the appendix Figure 9 Methods for obtaining the three-dimensional coordinate information of ground landmark models include:

[0106] Step F01) Select the landmark point of the ground landmark model;

[0107] Step F02) Read two aerial images 20 that both show the same landmark point;

[0108] Step F03) Calculate the three-dimensional coordinates of the object point based on the pixel position of the object point in the two aerial images 20 and the camera coordinates corresponding to the aerial images 20;

[0109] Step F04) Obtain the three-dimensional coordinate information of the ground object model based on the object points.

[0110] The method for selecting landmark points of the ground landmark model includes: marking the landmark boundaries of the ground landmark model elements and setting several preset landmark points on the landmark boundaries; obtaining the landmark boundaries and preset landmark points in the visible state according to the orientation of the boundary matching in the region of the ground landmark model elements, and using the preset landmark points in the visible state as the selected landmark points on the ground landmark model; obtaining the boundary corresponding to the landmark boundary in the aerial image 20; selecting two navigation points on the flight path, the distance between the two navigation points being less than a preset upper threshold and greater than a preset lower threshold, so that the aerial images 20 selected from two angles can find the boundary corresponding to the landmark boundary in both aerial images 20; and using the aerial images 20 corresponding to the two angles as the two selected aerial images 20.

[0111] The method for labeling the boundary of a ground object model element includes: labeling all vertices of the ground object model element, and using the lines connecting the vertices as the boundary of the ground object model.

[0112] Please see the appendix Figure 10 Methods for calculating the three-dimensional coordinates of a landmark point include:

[0113] Step G01) Establish the view area of ​​the aerial camera 70 on the sea level, denoted as the reference view area 80, and obtain the relative coordinates of each point in the reference view area 80 relative to the aerial camera 70.

[0114] Step G02) Obtain the pixel position of the target point in the aerial image 20, and then the coordinates of the corresponding mapping point 81 on the reference view area 80;

[0115] Step G03) The object point is located on the line connecting the camera coordinates and the mapping point 81;

[0116] Step G04) The two aerial images 20 will obtain the coordinate information of the two lines connecting the object point. The coordinates of the intersection of the two lines are the three-dimensional coordinates of the object point.

[0117] Please see the appendix Figure 11When aerial camera 70 is shooting directly downwards at an altitude H, the position of the field of view on the horizontal plane is only related to the position of aerial camera 70. By determining the three-dimensional coordinates of aerial camera 70 and combining them with its field of view, the three-dimensional coordinate information of the reference field of view 80 can be determined. The ground image captured by aerial camera 70 is aerial image 20, which has a certain altitude. The extension line connecting any pixel point on aerial image 20 to aerial camera 70 intersects the reference field of view 80, and the intersection point is denoted as mapping point 81. The coordinates of mapping point 81 can be uniquely determined by the pixel position of the corresponding pixel point in aerial image 20. Based on mapping point 81 and the position of aerial camera 70, an analytical expression for a straight line can be established in the geodetic coordinate system. The landmark point lies on this straight line.

[0118] Please see the appendix Figure 12 Then, by reading another aerial image (image 20), the analytical expression of another straight line can be obtained, and the landmark point also lies on this line. Solving for the coordinates of the intersection of the two lines yields the three-dimensional coordinates of the landmark point. By selecting several preset landmark points on the landmark model and obtaining their three-dimensional coordinates, the three-dimensional coordinate information of the landmark model can be obtained, thus enabling the complete construction of the landmark model and the completion of terrain mapping.

[0119] The method for obtaining the three-dimensional coordinate information of the ground object model based on the three-dimensional coordinates of the object points includes: substituting the three-dimensional coordinates of the object points into the ground object model after rotation and scaling to obtain the endpoint coordinate information of the object boundary of the ground object model; the endpoint coordinate information of all object boundaries constitutes the three-dimensional coordinate information of the ground object model.

[0120] The beneficial technical effects of this embodiment include: aerial images 20 are obtained through aerial photography, the acquisition efficiency of aerial images 20 is extremely high, aerial images 20 are associated with GPS coordinate information, and a terrain model is established with the help of the established ground landmark model, thereby quickly completing the terrain mapping; a terrain model can be established through the ground landmark model, which facilitates the use of various applications based on the terrain model; by dividing the area before establishing the ground landmark model, the efficiency and accuracy of establishing the ground landmark model can be improved.

[0121] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that the present invention includes, but is not limited to, the contents described in the accompanying drawings and the specific embodiments above. Any modifications that do not depart from the functional and structural principles of the present invention will be included within the scope of the claims.

Claims

1. A rapid terrain mapping method based on GPS, characterized in that, Includes the following steps: The flight equipment with GPS module carries a drone camera and flies along a preset route to record route information and periodically take aerial images. Associate aerial images with the GPS coordinates of the aerial camera; Read aerial images and build ground landmark models to obtain a set of ground landmark models; Based on the aerial images and the corresponding GPS coordinates of the aerial cameras, obtain the three-dimensional coordinate information of each ground object model in the ground object model set; A terrain model is established based on the three-dimensional coordinate information of the ground landmark model, and the terrain model serves as the terrain mapping result. Methods for establishing ground landmark models include: Create a region template; Use region templates to identify regions in aerial images; Establish ground landmark models for each area; Methods for creating ground landmark models for each region include: Establish ground landmark model elements for each region; Extract color blocks from each aerial image and obtain the boundary lines of the color blocks; Read two aerial images in which the boundary line appears, and calculate the three-dimensional coordinates of at least two points on the boundary line; Preserve the boundary lines that extend vertically or horizontally to obtain the preserved boundary lines in each aerial image; Merge identical preserved boundary lines from different aerial images, and group the merged preserved boundary lines according to region; After rotating and scaling the ground landmark model elements in the corresponding area, they are matched with the preserved boundary lines. If the match is successful, the ground landmark model is established based on the orientation and size of the rotated and scaled ground landmark model elements. Methods for establishing ground landmark model elements include: A road model element is established, which includes the road cross-sectional shape and the extension curve. After the extension curve is matched with the center line of the road area in the aerial image, the road cross-section extends along the extension curve to form a road model. A columnar building model element is established, which includes several preset base shapes and column heights. The base shape matches the base shape of the building in the aerial image, and the column height matches the height of the building in the aerial image. The base shape extends along the vertical line to reach the column height, thus forming a columnar building model. An irregular building model element is established, which includes several envelope curves. The envelope curves are located on a vertical plane. After the several envelope curves match the vertical cross-sectional shape of the irregular building, an irregular building model is formed. A square model element is established, which includes a polygonal outline. After the polygonal outline is matched with the square area in the aerial image, it is stretched to a preset thickness along the vertical direction to form a square model.

2. The GPS-based rapid terrain mapping method according to claim 1, characterized in that, The route information includes multiple waypoints, the coordinates of the waypoints, the timestamps of arrival at the waypoints, and the flight speed at the waypoints. Multiple waypoints are connected in sequence to form a preset route. The aerial images are associated with the shooting timestamps and the GPS coordinates of the flight equipment at the time of shooting.

3. The GPS-based rapid terrain mapping method according to claim 2, characterized in that, Methods for associating aerial images with the GPS coordinates of aerial cameras include: The relative coordinates of the aerial camera and the positioning point of the flight equipment are obtained. The GPS coordinates of the flight equipment are then superimposed on the relative coordinates to obtain the GPS coordinates of the aerial camera.

4. The GPS-based rapid terrain mapping method according to claim 1, characterized in that, Methods for merging and preserving boundary lines include: Merge collinear boundary lines; Merge mutually parallel boundary lines that are less than a preset threshold; Merge intersecting boundary lines with an angle less than a preset threshold.

5. The GPS-based rapid terrain mapping method according to claim 1, characterized in that, The area templates include road area templates, building area templates, plaza area templates, and green area templates. The road area templates include road color ranges and road surface feature matching sets. The road surface feature sets include pedestrian crossing matching templates, traffic light matching templates, and road shape matching templates. Color regions that match the road color ranges in the aerial image are extracted to obtain the envelope region of the color regions. Within the envelope region, the road surface feature matching set is used to match local regions of the envelope region. If a local region matches any matching template in the road surface feature matching set, the envelope region is determined to be a road region. The plaza area template includes a plaza shape matching template. Color blocks are extracted from the aerial image, and color blocks with pixel areas smaller than a preset threshold are removed to obtain the envelope of the remaining color blocks. If the envelope can be matched with the plaza shape matching template after rotation and perspective distortion, the area enclosed by the envelope is determined to be the plaza area. The green area template records the color range of the green area. Color areas in the aerial image that match the color range of the green area are extracted, and areas with pixel areas smaller than a preset threshold are removed. The remaining area is taken as the green area. The building area template includes several building outline matching templates. Color block edges are extracted from the aerial image. The building outline matching template is rotated, scaled, and perspective distorted, and then matched with the color block edges. If the match is successful, the color block edges are determined to be building edges. A polygonal area composed of polylines is used to enclose all building edges, and the polygonal area is regarded as the building area.

6. A GPS-based rapid terrain mapping method according to any one of claims 1 to 3, characterized in that, Methods for obtaining the three-dimensional coordinate information of ground landmark models include: Select the landmark points of the ground landmark model; Read two aerial images that both show the same landmark point; The three-dimensional coordinates of the object point are calculated based on the pixel position of the object point in the two aerial images and the camera coordinates corresponding to the aerial images. The three-dimensional coordinate information of the ground object model is obtained from the object points.

7. The GPS-based rapid terrain mapping method according to claim 6, characterized in that, Methods for calculating the three-dimensional coordinates of a landmark point include: Establish the field of view of the aerial camera on the sea level, denoted as the reference field of view, and obtain the relative coordinates of each point within the reference field of view relative to the aerial camera; Obtain the pixel position of the target point in the aerial image, and then the coordinates of the corresponding mapped point on the reference view area; The object point lies on the line connecting the camera coordinates and the mapping point; Two aerial images will yield the coordinates of the two lines connecting the target point, and the coordinates of the intersection of the two lines will be the three-dimensional coordinates of the target point.

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