We have conducted an aerial survey of about 21 000 Ha using an Ebee drone, with flight hights varying between 300m & 400m ASL. We allocated about 1200 GCPs roughly at 400m x 400m (some areas were not accessible).
The data was processed with Pix4d v.3.2.10 and v.3.2.4.
The following problems were identified on the data:
• Resulting DTM elevations do not match GCP elevations in all areas. GCPs were used as a framework to check the replication of the drone survey data.
• DTM elevations for the GCPs were determined using the “apply elevations from terrain layers to selected features” in Global Mapper
• Ridges created where different areas are merged
• Misalignment where 2 or more projects are merged
• When selected, GCP value changes instantly (Image below)
• DTM has wrong values along low-lying areas (water), please advise on what can be done to compensate for the wrong values
Please advise on the way forward to fixing these problems.
Thank you and Kind Regards