7 地形图测绘（7 topographic mapping）.docVIP

7 地形图测绘（7 topographic mapping） scale The ratio of the actual horizontal length of any line on the map to the corresponding line on the ground is called scale. Digital scale A digital scale is usually represented by a fraction of 1 and an integer of an denominator. 1:M = D: D = 1: (D/d) 1/1000 1:2000 M is called a scale denominator. The larger the denominator, the smaller the division value, the smaller the scale. Linear scale Draw a line scale on the map by scaling down the field horizontal distance. A scale represented by a line of length and a numeral note called a linear scale. Classification and size of scales 1, 5001,, 10001, 20001, 5000 large scale topographic maps 1, 10 thousand and 1, 25 thousand, 1,, 50 thousand and 1, 100 thousand, medium scale, topographic map 1, 200 thousand and 1, 500 thousand and 1, 1 million, small scale maps The size of a scale, that is, the magnitude of a scale. The larger the scale of the map, the more detailed the objects and landforms it represents The higher the point accuracy, but the smaller the surface area represented by a map, And the workload of Surveying and mapping will increase exponentially. Scale accuracy Significance According to the amount of distance precision of mapping scale selection On the map, the ground horizontal length of the 0.5m should be indicated, which should be used at this time A scale of not less than 0.1mm/500mm=1/5000. Determine the distance accuracy according to the scale The scale of mapping is 1/5000, and the field distance accuracy needs to be 0.1mm * 5000=0.5m, and the high precision will not be expressed. Topographic map schema The topographic map is the ground features and landforms formulated by the State Bureau of Surveying and mapping Symbolic name. Three types of schema symbols: I. symbols of objects 1. proportional symbols - large in outline and scaled down; 2. non proportional symbols - small outline, important, expressed by special symbols; 3. semi proportional notation - also known