What's the difference between digital line drawing (DLG) and topographic map?

1. Topographic map refers to the projection of the topography, geographical position and shape of the surface relief on the horizontal plane. Specifically, the ground features and landforms on the ground are horizontally projected (projected to the horizontal plane along the vertical line) and drawn on the drawings according to a certain proportion. This map is called topographic map, and its essence is projection map.

2. Digital line drawing (DLG): It is a vector data set of all map elements basically consistent with the existing line drawing, which keeps the spatial relationship and related attribute information among the elements and takes numbers as attributes.

Second, the application is different.

1, 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.

Topographic map is a common map made in accordance with unified specifications. It shows the basic geographical elements such as residential areas, roads, water systems, borders, soil quality, vegetation and so on in detail on the surface, and uses contour lines to represent the ground fluctuation. ?

2. DLG is applied to land use planning and control; Address selection of shopping malls, factories and transportation hubs; Urban construction management; Agroclimatic regionalization; Environmental engineering, air pollution monitoring; Road traffic construction and management. Monitoring and evaluating natural disasters, war disasters and other disasters; Changes in natural resources, human resources and landforms; People's livelihood industries (medical care, public utilities, services, etc.). ).

Third, drawing methods are different.

1. When drawing a topographic map with a piece of white paper fixed on the drawing board, the drawing board should be oriented first, 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 the surveying and mapping results required by the unified and standardized coordinate exhibition points should be included in the unified national basic topographic map; 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.

2. Digital line drawing (DLG) adopts digital photogrammetry and three-dimensional tracking stereo mapping. At present, the domestic digital photogrammetry software VirtuoZo system and JX-4C DPW system all have corresponding vector graph systems, with high accuracy. Among them, VirtuoZo system has workstation version and NT version, while JX-4C DPW system has only one NT version.

Analysis or computer-aided digital mapping. This method is to obtain DLG data by mapping aerial photos and high-resolution satellite photos on an analytical plotter or simulator. In this way, it is necessary to use graphic processing software such as GIS or CAD to edit the obtained data and finally produce the result data.

Scan the existing topographic map and vectorize its elements through human-computer interaction. At present, vectorization software, GIS and CAD software commonly used at home and abroad use vectorization function to vectorize scanned images and then transmit them to corresponding systems.

On the newly produced digital orthophoto map, the elements of the manual tracking framework are digitized. Screen tracking: You can use CAD or GIS and VirtuoZo software to insert the orthophoto map into the workspace according to a certain proportion, and then collect the corresponding elements on the map.

Baidu encyclopedia-topographic map

Baidu Encyclopedia-Digital Line Drawing