Massive Error on GPS

Hi Everyone,

Processed a job recently with high precision GCP’s, however when I Import the Point Cloud into AutoCAD it seems not insert where it should be. I went through the details in the report and I believe the GPS error is causing this problem.

Are there any known fixes for this issue or settings that can be changed in the processing to fix this. My guess is that the GPS coordinates on on some of the images where incorrect.

Any help is greatly appreciated.


Try to see your 2D map in WebODM result, then activate cameras layer.

Click one blue point randomly, see image’s name. You can also download camera shots and open it with QGIS to see that coordinate.

Then, please see that original image in GIMP to see EXIF metadata coordinate. It was same and correct?


This is highly unusual…

Do you remember this survey well? What was your preflight like? How many days since your sUAS was last powered on and flown? How long did you let it sit to acquire satellite lock?

This almost looks like it started collecting data before the GPS almanac was fully downloaded…

Thank you for the quick replies,

It been less than a week since our last flight. We do about 1-2 flights a week and have never had an issue until now.

This flight was on the 17/02. I did not encounter an GPS errors that I know of, but I use pix4d it did not give me any warnings before and during the flight. The GPS rover had around 20-30 satellites and was checked against permanent survey controls points in the area and residuals were within 10-20mm.

On the day the drone flew the grid perfectly and didn’t fly off anywhere strange, could this be due to errors in the gcp file? I had 15 GCP’s 2 were destroyed on the day and could not be used. I removed them from the file and used 13, however the final report only shows 8 that were used.

here are some screen shots from webodm:

Thanks for your help.

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Could you try to mask the area where your destroyed gcps are? Maybe the software interferes with the unused gcps

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I believe I have discovered what this issue was. Some left over images from a previous flight seem to have been uploaded into the project.

I have restarted the process and should find out in a couple of hours.

Thanks for all the help.


Aha! Yeah: that’d do it.

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