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Negative DSM Values

Hi there,

I did a drone flight using 30 RTK surveyed GCP’s in order to generate an accurate DSM to be compared against survey data. I set and surveyed 30 GCP’s with high accuracy RTK-GPS, but every time I generate a DSM, the resulting elevation values (ft) are negative and I cannot figure out why. I have tried just about every setting including using using the default Geoid setting, using the height above ellipsoid, and also arbitrary for veritical coordinate system. Reading forum posts and my own trial and error seem to point to using arbitrary as the best results but I still can’t get the correct values. Has anyone else experienced this or know of a solution?

Thank you,
Matt

Hi Matt,

Welcome to the Pix4D Community!
We would need more details to provide assistance in the most efficient way. Could you please send us the quality report? If you do not feel comfortable sharing your quality report in the Pix4D Community, feel free to open a support ticket (choose Personal Support) in the following link: Pix4D Support.
Other Pix4D Community members can still reply in this thread.

Cheers

hello, i have the same problem. What can i do?. Thanks you!

Hi @nicolaspaz,

Welcome to the Pix4D Community.

Is it possible that the elevations are negative? Where is the project located? What are the elevation values in the GCPs you are importing and what is the vertical reference for the GCPs?

You can share your GCPs and your quality report here. If you don’t want to share these files in this public thread and if you have a license eligible for Personal Support, I suggest you open a support ticket choosing Personal Support in the following link: Pix4D Support.

You can also watch this page in order to be notified once a reply is posted.

Cheers.