Photogrammetry is a two-dimensional imaging technique that can be used to create elevation models, but it is unable to penetrate dense forests or scrubland.
Lidar, on the other hand, does not actually see through vegetation. This process involves the LiDAR unit sending out a pulse that is then reflected back when it collides with the vegetation. The unit is then programmed in such a way that when the first beam returns, it meets the second beam that has just been sent out from the scanner.
In summary, aerial Lidar alone cannot capture information about stems and branches, while LIDAR SLAM (simultaneous location and mapping) lacks the ability to generate dense point clouds near the treetops (the two methods work together). Barry Gregg is an expert in Lidar data engineering and chief pilot of unmanned aerial vehicles with over 10 years of experience in the utility engineering industry.