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How to draw elevation projection map of foundation pit

Foundation pit elevation projection, specific steps:

Step 1: Cut the terrain surface with a set of equally spaced horizontal planes to obtain a set of horizontal intersecting lines, which are called contour lines.

Step 2: project onto the horizontal projection plane (datum plane) and mark their respective elevations to obtain elevation projection map, also known as topographic map.

Step 3: The height of the section above the datum is called elevation or elevation, and the unit is m..