The Meaning of GCP's moving from coords after processing pt cloud?

[jmaeding]

I've been using metashape for a few years now (was PS), and ran into somthing I need to understand.
I'm a civil that flies a phantom 4 pro, and has GCP points on the ground.
I use the USGS workflow I have posted here before, and generally get super good clean results.
I had a run though, where after processing the control points show quite a bit above the ground.
It occurred to me to uncheck the markers and I realized there is a "real" location, and "compiled" one - wow.
If I uncheck the markers, they show at coords I gave them and are right on the ground.
Now I am wondering what to think of this. Why would the results be essentially correct, yet the markers moved vertically after processing?
I know unchecking makes them check points. Does a large difference (more than 1 foot) between original and final location indicate anything is bad?

I'm literally facing my boss and client, wondering if I should use the data or discard and refly.
thanks

[Alexey Pasumansky]

Hello jmaeding,

If the onboard GPS is not RTK, then 1 foot error could be just related to the low accuracy GPS.

However, another possible reason of the problem is the altitude information recorded by DJI - it could be written over the sea level or over the take off point, while by default Metashape expects the height above ellipsoid.

[dpitman]

Hi jmaeding,

If your drone uses a consumer gps, are you using the step of giving greater accuracy weight to the markers over the cameras as recommended in the OLD official tutorial (screenshot attached)?

Note, this seems like a critical step, but is missing in the new official tutorial and I asked if it is not longer officially recommended but received no reply. https://www.agisoft.com/forum/index.php?topic=12551.0