What is an electronic map

Usually the maps we see are based on paper, cloth, or other objects of real size, and the map content is drawn or printed on these carriers. The electronic map is stored on the computer's hard disk, floppy disk, optical disk or tape and other media. The map content is represented by numbers. These numbers need to be displayed, read, retrieved and analyzed by special computer software. The amount of information that can be represented on the electronic map is much greater than that of ordinary maps. For example, highways are marked with lines on the ordinary map to indicate their location. Different symbols such as the shape, width, and color of the lines indicate the grade and other information of the highway. On the electronic map, the location is represented by a series of X and Y coordinates, and the grade and other information of the highway are represented by the attributes of the line, such as '1' for expressway, '2' for national highway, etc., line drawing on the electronic map There can be many attributes, such as highway grade, name, pavement material, starting and ending point name, road width, length, traffic flow, etc. can be recorded as a road attribute, which can describe the road more comprehensively, these are common The simple symbols of the map cannot be represented.

Electronic maps can be very convenient for any form of element combination and splicing of the contents of ordinary maps to form a new map. The electronic map can be output on any scale and in any range. It is very easy to modify and shorten the time for drawing. It can be easily combined with other information sources such as satellite images and aerial photos to generate new types of pictures. You can use the information recorded on the digital map to derive new data, such as the contour lines on the map to represent the geomorphic form, but it is difficult for non-professionals to understand. The contour lines and elevation points of the electronic map can be used to generate a digital elevation model to undulate the surface. Represented in digital form, it can intuitively and three-dimensionally represent topography. This is that the ordinary topographic map can not achieve the performance effect.

The National Surveying and Mapping Bureau has nationwide electronic maps of 1: 4 million, 1: 1 million, and 1: 250,000. In the future, it will also produce 1: 50,000 electronic maps. These are important components of the national basic geographic information system. They are other Carrier of professional information management and analysis of various departments. Various provinces and cities surveying and mapping and urban planning departments have produced a large number of large-scale electronic maps, such as 1: 5000, 1: 2000, 1: 1000, etc., which can be used in many departments such as urban planning and construction, transportation, tourism, car navigation and so on. All these digital maps turn the daily work of various departments from a large number of original maps to a pre-computer operation, which is scientific, accurate and intuitive, and greatly improves efficiency.

There are many types of electronic maps, such as topographic maps, raster topographic maps, remote sensing image maps, elevation model maps, various thematic maps, and so on.