We usually use contour maps for field work. Of course, if a professional gravity magnetic map or theodolite or GPS is more useful than a contour map, but it is used by professionals, we do not need to be able to obtain it.
Contour map is to connect the points with the same surface height into a circle and project it directly to the plane to form a horizontal curve. The loops with different heights will not match, unless the surface shows cliffs or cliffs to make the lines appear too dense and overlapping. The flat and open slopes of the outlet line are quite wide, and its baseline is based on the average sea level of the sea level. There are marking instructions at the bottom of each map to make it convenient for users to use. There are scales, figure numbers, map join tables, legends, and orientation angles.
The scale is the symbol that must be marked on the map. It is the proportional correlation that shows the actual distance between the surface and the distance between the maps. For example, a map with one hundred thousandths shows a centimeter, that is, a map with an actual distance of one kilometer and one ten thousandth of a map. It represents one centimeter, that is, the actual distance is five hundred meters. For the accuracy of maps and actual distances with different scale ratios, the accuracy of the map with small scale is higher. Scale and Actual Distance Conversion Table Map Scale Field Distance (meters) Map Distance (cm) 1:25,0001,00041: 50,0001,00021: 100,0001,0001
The map number is a number that represents the name of the map. Different scales of maps are coded in the respective systems, and it is based on latitude and longitude so that each map can be closely linked.
The azimuth declination angle is the angle that positive north (earth north pole), magnetic north (magnetic needle shows north), and grid north (map indicates north) are deviated from each other. At the same time, the year-by-year magnetic variable value is attached to the figure below. We can use the north arrow to indicate our position and then map the map so we can quickly know where we are and where we are going and where we are going.
The legend is to explain the meaning of various symbols on the map. Generally, the symbols that the climber pays attention to are triangle points, wall collapses, rivers, lakes and slopes.
Contour maps and terrain analysis
First, the type of contour
A detailed view of the contour map will show that there are two types of lines: the thickness and the fineness of the line drawn on the map. This is convenient for users to read and design. The thick line measures the curve and indicates the altitude, and the distance between the curves is 0.2 centimeters. The first curve, which is between the metering curves, has the function of facilitating analysis of the terrain. There are four head curves between each two meter curves, so the distance unit between each line is 0.04 cm, and the interval between the contours of the map Actual Distance Units Contours Actual Distance Scale Gauge Curve 1 : 50,000 100 Meters 20 Meters 1: 25,050,050 Meters 10 Meters 1: 10,000 25 Meters 5 Meters
Second, the blind spot of the contour
The higher the scale, the poorer the precision is because the actual distance between the contours is too wide and the terrain in this space cannot be clearly identified and the blind spots appear. Take the map of 50,000th of an example as an example, the distance between each curve is The actual distance is 20 meters (equivalent to the height of the seven-story building).
Third, slope
The slope contour contour map is one of the most easily recognizable features of the terrain. We can understand the slope of each peak by observing the map roughly. For example, the narrower the distance between the curves, the steeper the slope, the wider the curve spacing, the slower the gradient. The uniform spacing of the curves indicates that the section is equal slope, if the spacing above is less than the spacing below, it means that the section is a concave slope, and vice versa.
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