Hi, I would like to know what is the priority of the alignment for GCP and distance constraint versus the position prior hardness and orientation hardness? and is the position prior hardness and orientation hardness relative? setting it 0.7:0.3 = 7:3?
The reason is I have a project with 5 GCP, 5 CP, also with distance constraint. The images are taken by drone with GPS but not in good quality (no RTK).
The alignment is considered successful given 2530 out of 2783 are aligned in single component. However the model is rotated and incorrectly scaled and shifted giving a very large error in GCP (more than 80 meter) and error in distance constraint. I configured 0.36meter but the result is 0.013.
My control point prior settings are using default.
I wonder why the GCP and distance constraint are not given higher priority to follow during alignment.
Hello,
in that cases (as you have the drone data with no good quality) it is better to turn off the camera priors and use the GCP information for the georeferencing.
The reason we asked for that is to understand what should be the correct value assigned in the weight. right now the alignment give quite random result to project with less accurate image position. Sometime it seems doesn’t follow the distance constraint defined at all. So we would like to know how’s the priority of the GCP constraint and distance constraint weight against the orientation constraint and position. From the data if we ignore camera priors, then orientation data are not used as well. However I think the orientation from drone would still be quite accurate even though the position is not.
There is no a “correct” value, as each measurement could be different.
The camera priors have the higher priority as the constraints (but I not not aware on the values for those), so if the camera prior poses are not so precise, the constraints could be different to the original one. But you can try to set its accuracy to 0.
It really differ on the case and it is basically the playing with the values.
The best option is to avoid using camera priors at all. With properly measured GCPs the orientation of the model will be proper.
As you think, that the camera orientation is right, then you can set the accuracy to lower values and the hardness to bigger and opposite for position accuracy in the Alignment settings:
