第三节地图（Third section map）.docVIP

第三节地图（Third section map） A series of horizontal curves are formed. If these horizontal curves are projected onto a standard horizontal surface and scaled down in a certain proportion, the contour map of the contour can be reflected on the drawings, which can reflect the height of the ground. The contour elevation is from sea level to measure the. The starting point of terrain elevation in China is unified with the the Yellow Sea standard origin of Qingdao. Since the above sea level, a contour line can be set at a certain height difference, and the elevation difference between the two adjacent contour lines is called equal distance. The choice of height distance is determined by the scale of topographic map and the features of terrain fluctuation. Generally speaking, the larger the scale and the smaller the distance, the more detailed the topographic representation can be. In contour maps, contour lines must be marked with elevation. The features of relief are represented by a series of contour lines marked by elevation. The contour of intensive, and the ground slope steep; sparse contour, gentle slope on the ground. If the contour interval is very uniform, that even if the height of slope; sparse contour, downward gradually intensive, that relief under the steep slope; if the contour of the high dense, downward slope steep thinning, that slowly. 7. there are so many kinds of maps that they can be classified according to many signs. According to the size of the scale to divide, there are three types: (1) large scale maps (1, 100000, and 1 + 100000); (2) middle scale map (less than 1: 100000 to greater than 1: 1000000); (3) small scale maps (1 and 1000000 and less than 1. 1000000). On a map of the same size, large scale maps can only reflect small spatial extent, while small scale maps can reflect larger spatial extent. According to the map of the space (region) range, can be divided into world map, hemisphere map, mainland map, ocean map, continents map, national map