Hi everyone, first post here been reading a lot and only just now have something to post.
A friend asked me to help him better understand poor drainage on his farm. I flew 2 missions, one with a DJI Phantom 4 Pro and second with a Skydio 2, both using identical planned routes / elevations / overlap / etc in dronedeploy and performed on the same day back to back. Processed both with webodm, each flight containing just under 300 photos, no GCPs, keeping mostly defaults and cutting the workflow a bit short of all products after a few failed attempts. Orthophotos look great, but to solve his problem i must rely on elevation outputs, which seems to have 2 strange issue that i need help understanding.
- both show water features in the correct direction (drop off from higher land down to water), but the maps overall show the opposite shape. the phantom 4 pro is bowled with the middle part of the image being low, and the skydio is a dome with the middle being high.
- the elevations from the skydio generally match (or relatively close) to a LIDAR dem that i found that the county had acquired a decade ago, which has 5m resolution but i think should be fine for general comparison. However, the phantom 4 pro shows negative elevations ranging from -10 to -29m compared to the skydio ranging from 37 to 63m. For reference, the image of the lidar dem is scaled identical to skydio image, 37 to 63 and all 3 using the same colorbar.
Any feedback that can help me understand what is happening would be much appreciated. For a start there are some interesting features that are visible, but if the elevations are totally wrong not only in value, but also in generic shape, then it doesn’t help much.
sorry to scrunch them all into powerpoint… apparently new members are only allowed a single upload.