Hi folks, a complete novice here so I apologise if this question is basic. I have UAV photos of a dense woodland canopy and I plan to use the DTM and DSM produced in Pix4DMapper to create a Canopy Height Model (CHM) to use in further works. It is my understanding that the DTM and DSM produced in PIX4D is based on the photogrammetric point cloud that is also produced. Can anyone suggest any ways in which to improve the point cloud in order to produce a better quality DSM and DTM? Further to this, I am aware that the point cloud itself can be exported to create a DSM and DTM in other programmes- is it worth doing this to create a better quality DTM/DSM?
HI Scarlet,
First, PIX4Dmapper can generate both the DSM and DTM. There is no need to do this in a thrid party program.
More importantly, heavy vegetation is notoriously difficult to map. It has a complex geometry that can move in the wind. The result is that it can be difficult to generate a sufficient amount of common keypoints between images.
There are two solutions: First, keep your overlap very high. Perhaps in the 80-90% range. This will help. Secondly, it can be beneficial to drop your image scale to 1/2 or lower under step 1. This tends to negate the effects of the vegetation.
Can you tell me why dropping the image scale helps?