What is the difference between DEM, DSM and DTM?

A DEM is a 'bare earth' elevation model, unmodified from its original data source (such as lidar, ifsar, or an autocorrelated photogrammetric surface) which is supposedly free of vegetation, buildings, and other 'non ground' objects.

 

A DSM is an elevation model that includes the tops of buildings, trees, powerlines, and any other objects. Commonly this is seen as a canopy model and only 'sees' ground where there is nothing else overtop of it.
(A DTM(is effectively a DEM that has been augmented by elements such as breaklines and observationsother than the original data to correct for artifacts produced by using only the original data. This is often done by using photogrammetrically derived linework introduced into a DEM surface. An example is hydro-flattening commonly seen in elevation models done to FEMA specificationsdigital surface models)is effectively a DEM that has been augmented by elements such as breaklines and observations other than the original data to correct for artifacts produced by using only the original data. This is often done by using photogrammetrically derived linework introduced into a DEM surface. An example is hydro-flattening commonly seen in elevation models done to FEMA specifications
DTM(digital terrain models): bare-earth representation with irregular spaces between points (non-raster).
DEM(Digital elevation models): gridded raster representation of the DTM.

 

DEM是指真實地球的數值高程模型，所謂"真實"指地球表面的自然地形起伏，以原始數據源進行儲存，未進行任何修改，所以也不包括地表上的植物、人工建築物及其他非自然地貌的起伏物體。
DSM是另一種數值高程模型，與DEM不同之處在於它允許包含人工建築物、植物、樹木甚至電線杆等物體的頂部。(請查看左示意圖)
而DTM可以視作一種強化後的DEM，它強化了地形的輪廓線，並且透過航照照片進行校正。