[GRASSLIST:5048] difficulties with i.ortho.photo

[Guillaume Criloux]

Hello,

I am using i.ortho.photo to ortho-rectify aerial images of Mayotte (Comoros Archipelago).
The associated man pages are not very clear about a few points.

When i register a camera, what is this "point of symmetry" that i have to locate on the photo ? What is the origin and direction of X and Y on the photo ?

When i must enter fiducial and reseau marks, where is the origin ? is it the same as the point of symmetry that i talked about above or is the point of symmetry the new origin ?

Well, if someone has experience in using i.ortho.photo and explain me a bit, i'd be very grateful.

Thanks in advance,

Guillaume Criloux.