nDSM、CHM、DTM、DEM、DSM, Shear constantly 、 But it's clear
at present , Around the theme of terrain products , Mapping 、 Geographic Information 、 Forestry and ecology 、 geological 、 Civil engineering and other fields are common DTM、DEM、DSM、nDSM、CHM、DCM And other English abbreviations . These abbreviated English professional terms are often confused , Even some professionals have mixed use , Many Xiaobai users are confused . So , This tweet especially arranges the above related concepts , To clear up the source .

1、 Digital terrain model （DTM）

2、 Digital elevation model (DEM)

3、 Digital surface model (DSM)

chart 1 DSM And DEM、nDSM Schematic diagram of connection and difference

4、 Normalized digital surface model (nDSM)

Normalized digital surface model (normalized Digital Surface Model, abbreviation nDSM) It is an elevation model that reflects the vertical height from the ground to the ground .

In order to eliminate the influence of topographic relief on feature extraction , The extraction of laser points of ground objects is often in nDSM In the . airborne LIDAR After filtering the point cloud data , The regular grid is interpolated from the selected ground points DEM, then DEM Resampled from the original point cloud data DSM Subtract from , To generate nDSM. chart 1（b） by nDSM Generation diagram of .

in addition , at present nDSM The forms of expression are becoming more and more diverse . In addition to reflecting the height information of features , Currently available nDSM It also integrates semantic information , Pictured 2（a） Shown ; yes , we have nDSM It can fuse the height and semantic information of ground objects at the same time ）, Pictured 2（b） Shown .

（a） Fusion of semantic information nDSM

（a） At the same time, it integrates semantics and ground object height information nDSM

chart 2 A new method combining the height and semantic attributes of ground objects nDSM

5、 Canopy height model （CHM）

Canopy height model of vegetation （Canopy Height Model,CHM） It is a surface model expressing the height of vegetation from the ground , Usually based on digital surface model DSM And digital elevation model DEM, adopt CHM = DSM–DEM, Generate CHM. in addition , In the field of forestry and Ecology ,DSM It is also commonly referred to as DCM（Digital Canopy Model）.

Generally speaking ,nDSM And CHM It is the specific appellation of the same product in different industries . To be specific , In the field of Surveying and mapping nDSM Essentially equivalent to Forestry 、 Ecological field CHM.