Hi Photoscan community,

I am hoping to get help in wrapping my head around a problem I am experiencing.

I was given truncated coords for my GCPs, I converted these into standard UTM to assist in pinning the GCPs within Photoscan.

After pinning the targets, instead of importing the truncated target coords back in, I optimized the sparse point surface based on my converted UTM coords... This is where I am lost. The optimized surface based off the UTM coords has an average error of 2cm. When I import the truncated coords back in, the error sits around 30cm...

I screwed up further by going ahead and building the dense point surface before importing the truncated coords and finding out about the error... Worse yet, I have spent a day filtering this Dense point surface that took 2 days to process.

I am assuming that I will need to go back and optimize the sparse point surface based on the truncated coords to correct this then rebuild the dense point surface and then start filtering again.

My question to the community is, Where does this error come from? when going back and forth between truncated and non-truncated coords, isn't the model just shifting in x/y space? the elevations are unchanged between the two coord systems... Photoscan is telling me that the error is in the elevation values however... Why is error being introduced in elevation from a simple x/y shift?

If anyone can help me wrap my head around this it would be greatly appreciated.

Thanks