Photoscan ignoring my very accruate GCP, and assigning it significant error

[dellagiu]

I have a project (attached) where PhotoScan appears to completely ignore my only ground control point (GCP). I would like to "force" PhotoScan to keep the error low at this point. This GCP is highly accurate. I do not understand why PhotoScan is ignoring this point.

I have triple checked that all of the following information is correct, although there is little documentation about appropriate units, etc., for PhotoScan's Ground Control options:
- Latitude and Longitude of every camera (in degrees)
- Altitude of the camera (in meters) defined with respect to the surface of the planet
- Latitude and Longitude of my single GCP (in degrees) which is highly accurate
- Altitude of the GCP (in meters) defined with respect to the surface of the planet,  which is highly accurate.
- Focal length of each camera (mm)
- Pixel size (mm)
- Planetary coordination system (.prj file in WKT format) for Mercury

As you can see, when I incorporate my GCP into the bundle adjustment, PhotoScan Pro think's it is wrong and assigns it a HUGE error. My assigned value is 1832 m but PhotoScan believes it is 353250 m, that is roughly incorrect by a factor of 200!

This cannot be correct. Despite this, I am getting a very low re-projection error (<0.2 px).

What is going wrong here? Are these errors arising from the fact that I am using a different planetary coordinate system?

[Alexey Pasumansky]

Hello dellagiu,

Actually I have not so much experience working with other planets, but at the moment can suggest to specify different weights for camera and marker accuracy in the Reference pane settings dialog.
Also are you confident in the coordinates of the last camera in the list? It seems to be hundreds of kilometers away from others.

[dellagiu]

Hi Alexey,

Thank you for that advice! Yes, I am highly confident in the camera positions. I used your advice and changed the weights the in the Reference pane settings dialog, and now seem to have low errors and good results (attached).

Unfortunately, now the problem is that when I try to build the point cloud I get the following error: "Cannot build dense cloud".

Before, I was able to build the dense cloud and got beautiful results--but the elevation was wrong and I had huge errors. Now I am getting small errors, but no results...do you have an idea of what is the problem?

I am also attaching the coordinate system I am using, for reference.

[Alexey Pasumansky]

Hello dellagiu,

I think that just the bounding box now doesn't contain the area of interest. Try to use Reset Region command from Tools menu and then build dense cloud.

[dellagiu]

Thank you Alexey -- I'm not sure what the problem was, but I upgraded to the most recent version of Photoscan and now I am getting good solutions.