How is the terrain drawn?

Topographic mapping adopts manual mapping photography, aerial photography mapping and space remote sensing mapping.

Firstly, the sketchpad should be oriented, which can be oriented according to the geodetic control points measured in advance as the starting direction; In simple drawing, compass can also be used for orientation.

After the drawing board is oriented, it is necessary to determine the position of the drawing point on the map, and there are unified and standardized coordinate points to be included in the national unified basic topographic map for surveying and mapping; But for small-area surveying and mapping, we can assume the independent origin of the plane rectangular coordinate system, and then we can begin to measure the plane coordinate position of any other point on the ground by measuring the azimuth and distance.

As for the elevation of points, height system has laid out many leveling points with uniform elevation datum for use throughout the country, and generally, it can continuously measure the mapping area by leveling. Therefore, the point and elevation of any point can be determined at the same time by using the method of trigonometric leveling in surveying and mapping.

Geomorphology can reflect its height and morphological changes through contour lines; Features of houses, roads and rivers. Can be represented by lines formed by their transformation feature points; There are many special landforms and features and special legend symbols to represent them.

Therefore, the work of mapping topographic map is actually to measure and represent the characteristic points of all landforms and features on the ground. Of course, topographic maps of different scales also have a problem of feature point selection and comprehensive complexity.

With the development and progress of surveying and mapping science and technology, a lot of heavy surveying and mapping work of modern topographic maps has also changed from traditional field white paper mapping to indoor aerial photography mapping and space remote sensing mapping, and gradually moved towards full digital and automatic mapping.

Extended data:

Because the area of surveying and mapping is relatively small, it can accurately and in detail represent natural geographical elements such as topography, hydrology, soil and vegetation, as well as social and economic elements such as residential areas, traffic lines, boundary lines and engineering buildings.

According to topographic survey or aerial photography data, the error and projection deformation are very small. Topographic map is an indispensable tool in economic construction, national defense construction and scientific research; It is also the basic data for compiling various small-scale general maps, thematic maps and atlases. Topographic maps with different scales have different specific uses.

Ordinary maps made according to unified specifications show the basic geographical elements of the surface in detail, such as residential areas, roads, water systems, borders, soil and vegetation. , and use contour lines to represent the ground undulation.

References:

Baidu encyclopedia-topographic map