Constrained camera altitude but not horizontal position

[Mycobiont]

I have a project with no GPS camera positions, but I do have good 3D GCP positions.  The project is for underwater topography and there is a lot of noise in the tie points due to light ripples on the ground surface.  Modeling camera positions is going ok, but I often have camera positions modeled too high or too low.  All camera positions were taken from just below the surface of the water, so I do know the altitude +/- about 20 cm.  It would be great to specify the camera Z-values and an associated accuracy without needing to specify X and Y.

[Alexey Pasumansky]

Hello Mycobiont,

You can use approximate X and Y values on input and define separate accuracy for XY coordinates (like hundreds or thousands of meters) and high accuracy on Z.

[Mycobiont]

Wow! That was not very obvious, but didn't take too long to figure out.  I'm on version 1.6.5 and only saw the single edit box for camera accuracy in the Reference Settings and the single column in the Cameras table within the Reference pane.  So I had not realized this was possible. 

For others, this is what I did to implement Alexey's suggestion.  First "Export Reference" for Cameras.  My project had some of the cameras well aligned with coordinates based on GCPs, so I included the "Save estimated values".  Saved that and opened it as a spreadsheet. I calculated average values for cameras with estimated X, Y, and Z values.  I used the average X and Y for cameras that had no estimated values and the average Z for *all* cameras.  Then added 3 more columns for the accuracy of X, Y, and Z.  For cameras with X and Y positions, I figured 3 meters is reasonable accuracy for my project; 200 m for cameras that are using the averaged X and Y values.  Then I set 0.5 for the Z accuracy of all cameras.  Back to MetaShape, Import Reference, set the columns for Label, X, Y, and Z, then checked the box for "Accuracy" and set the columns for X, Y, and Z accuracy.

The result was that the Reference table for Cameras now has values like "3/0.5" in the accuracy column. 

[Alexey Pasumansky]

Hello Mycobiont,

Does it give you the desired orientation of the model?