What’s the difference between a DTM, DSM, and DTM? Several People have different Views on this so I am posting definitions from Keith Cunningham, Which I agree with.
DSM – Essentially the full point cloud, with ground, structures, and vegetation. (cheapest)
DEM – Bare Earth with structures and vegetation removed
DTM – DEM with thinned ground points (mass points) and breaklines. (most expensive)
WiLDER LiDAR Blog 
Thanks for codifying these terms!
It seems everyone has their own ideas about what these terms translate to. It can be difficult to have a discussion and can quickly become a debate about terminology.
I am going to update this section from The DEM Manual second addition but you are correct on the debate.
Great post! I would also add nDSM (Normalized Digital Surface Model), which is the height of features relative to the ground, or the DEM subtracted from the DSM. Some people use the term “canopy model,” but I really disagree with this as the nDSM includes buildings, power lines, etc.
Its nice to read your post jaralath then if we would want to extract the plant height so we have to minus DTM from DSM? or any other method??
Shakir,
Can you clarify what you are asking? if you take the buildings and man made features out of you data and compare the Ground (DTM) to the vegetation ( maybe DSM) you can get plant height.