How to build DEM

Jun 30, 2023

There are many ways to build DEM, classified from the way of data acquisition:

1) Measure directly from the ground. The instruments involved include components such as horizontal guide rails, styli, stylus holders, and relative elevation measurement boards. High-end instruments such as GPS, total station, and field measurement can also be used;

2) According to aerial or aerospace images, it is obtained through photogrammetry, such as three-dimensional coordinate instrument observation and aerothree encryption method, analytical mapping, digital photogrammetry, etc.;

3) Acquisition from the existing topographic map, such as grid reading method, digitizer hand-held tracking and scanner semi-automatic acquisition and then generate DEM through interpolation.

There are many DEM interpolation methods, mainly including overall interpolation, block interpolation and point-by-point interpolation:

1) The fitting model of overall interpolation is established by the observation values of all sampling points in the study area;

2) Block interpolation is to divide the reference space into several blocks of the same size, and use different functions for each block;

3) Point-by-point interpolation is centered on the point to be inserted, defining a local function to fit the surrounding data points. The range of data points changes with the position to be inserted, so it is also called moving fitting method.