I am generating an orthophoto and DSM from imagery collected with no camera GPS location and very few ground controls. X,Y Ground control is derived from 0.1 m orthoimagery from a few months ago, and Z ground control is from 2-year-old 1 meter Lidar DEM.
In Ground Control Settings:
/Camera accuracy - is this for camera position? Does this setting matter if I haven't specified GPS locations for camera? I have left at default 10 meter for now. When/why would I change this?
/Marker accuracy - I estimated 0.25 meter since my imagery and the orthoimagery have similar (~0.1 m) resolution. Does this value represent my certainty that I picked the right pixel for my markers?
/Projection accuracy - this is at 0.1 pixels. What does it mean? when would I change this?
Finally, if I change these values (and if not), do I want to optimize photo alignment after I add GCPs?
If I understand the manual and the process in PhotoScan Pro correctly, I think that I want to accurately constrain my error, optimize photo alignment, then produce the orthophoto and DSM. I want to see if I can use the imagery to measure volumes of eroded sediment (from a dam removal project), so I am very concerned about accuracy and will be comparing to Lidar that will be flown in a couple weeks. I think that some explanation and clarification could save me hours of trying different settings.
The imagery is of a river, so the three GCPs that I have defined are oriented mostly linearly (see screenshot). I have considered adding a fourth, but I have poorer quality coverage (fewer photos, more noisy surface) further from the river.
I am using ground features like road centerlines and centers of manhole covers and boulders as control, and I am trying to understand the proper settings for measurement accuracy in the ground control settings. Also trying to determine whether I want/need to recalibrate camera positions.