I am starting to plan the construction of a small plane to do photogrammetry, in special to do 3D mapping and the DSM.
I'm stuck in two questions:
- What is the resolution that you need to do, for example, a topographic map?
I saw some application and people used most of the time 1 to 5 cm of GSD, but is there any technical explanation or rule of thumb for this?
- Is it necessary to have an oblique camera to do 3D mapping or it is enough to have just the one facing downward?
If is necessary, what usually is done? You put two cameras or do the survey two times changing the position with a gimbal?
Thank you a lot!