Who has the information to make a 3D map?

In particular to a method for drawing topographic maps of various scales by using photogrammetry and remote sensing technology, in particular to a method for making three-dimensional visible and measurable topographic maps of urban areas. The invention is realized by the following steps: (1) data acquisition; (2) 3D modeling of urban buildings; (3) three-dimensional map decoration; (4) equidistant projection transformation; (5) blanking the three-dimensional model; (6) rendering the three-dimensional model; (7) carry out plane trimming on that generate three-dimensional effect diagram; (8) The output is graphics. Because the topographic map making method and principle on which the invention is based are basically unchanged, the new three-dimensional urban topographic map is also the natural development and extension of the traditional topographic map; The three-dimensional topographic map of the urban area is three-dimensional, that is, the urban landscape can be observed, and the height of the building can be distinguished by vision; The specific height of urban buildings can be measured, and the measurement accuracy depends on the surveying scale. The invention is suitable for making three-dimensional digital topographic maps with various scales and perspectives.

1. A method for making three-dimensional visible and measurable topographic maps of urban areas, which is characterized by adopting the following steps:

(1) data collection: collect the three-dimensional coordinates of the building frame through vector digital map data and DEM data, and collect the specific height h of each building;

(2) Three-dimensional modeling of urban buildings: according to the collected data of the frame and height ratio of buildings, the frame of each building is moved up by the height ratio h along the Z axis to form the outer contour line and the top surface of the building, and the corresponding points are connected to form the side surface, so as to establish a three-dimensional data link describing the relationship among building objects, surfaces, lines and points;

(3) Three-dimensional map arrangement: according to the given viewing angle α, a three-dimensional data link between the three-dimensional ruler and the map outline is set at the intersection point of the grid inside the map sheet, and the three-dimensional ruler is also set at the four corners of the map sheet, and the three-dimensional data link of the measuring scale is marked;

(4) Isometric projection transformation: for the three-dimensional model of the building, the outline of the building is projected from the space to the plane according to the given viewing angle α, and the mapping relationship between the three-dimensional vertex and the two-dimensional plane of the building is established, and the inflection points of the outline with the same name are connected to form a visual model with stereoscopic effect and measurable building proportion;

(5) Three-dimensional model blanking processing: firstly, drawing the bottom surfaces of all building models; Secondly, according to the distance from the side of all three-dimensional models of the building to the viewpoint, they are sorted from far to near and drawn separately.

③ According to the top-to-surface ratio of all building models, they are sorted from low to high, and drawn in the order from low to high respectively;

(6) 3D model rendering: according to the 3D model of the city and the simulated illumination, each face in the model is colored by mathematical simulation method to generate an image of the 3D model of the city;

(7) The plane completes the generation of three-dimensional renderings: ① The city three-dimensional model image, the surface vector layer and the orthographic image layer are superimposed; ② Add 3D scale and 3D effect examples on the periphery of the map;

(8) Drawing output: according to different requirements, output or store the above drawings.