hughk t1_iuefikk wrote
How do they penetrate the tree cover? Isn't there going to be a lot of reflection from leaves? I know tree cover is normally Farr from 100% but it must still must be quite a challenge.
Northern_Chap t1_iueo0cg wrote
The algorithms can determine differences in height returns from the thousands of readings and determine the difference between ground and canopy.
Most returns may find canopy in this scenario, but when there are sporadic but consistent drops in heights it can determine if it is an outlier/error or part of the ground etc.
mistoplus t1_iuempwf wrote
You are right, most of the measurements correspond to the forest canopy. However, the latest lidar sensors use very high frequencies and shifting angles, so some laser beams do get to the ground. The resulting point clouds are then classified by applying different algorithms (High vegetation, low vegetation, ground, etc.) and you can apply filters to create a surface from assumed ground points only. It's not perfect, but still very very good.
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