If the GCP analysis report shows few or no detected targets, the cause is usually one of three things: the targets are too small in the images, the target pattern is not the supported black and white checkerboard, or the images lack camera intrinsics.
Targets too small
Check the target size and the flight altitude before you process. A target that covers only a few pixels is not found, and a very low or 0% recall in the report points to this. Existing images cannot be repaired afterwards: fly again lower, or with larger targets, or process without GCPs.
Unsupported target pattern
Automatic detection needs the black and white checkerboard pattern. Replacing GCP coordinates does not help if the pattern is not supported.
Missing camera intrinsics
If the processing report shows Camera Intrinsics are 0,0, the images lack usable camera metadata. This was seen with DJI M4T and Terra imagery. Do not change the GCP file: the problem is in the image metadata, not in the CSV or the coordinate units.
Processing without GCPs
Processing can finish without GCP referencing. Then the accuracy depends on RTK or PPK of the images. In one case a vertical offset of about 20 cm remained. Tell your client about the limit.
Success is two different things
A processed model does not mean the GCPs were used. Read the GCP analysis report to see whether they were.
What to send to Sodex Support
- Project, data model name, and the time
- The GCP analysis report
- Image source (camera, app), and flight altitude
- Target size and pattern
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