I have to find the camera position using several images from a football field. Using these images I can find the homography that transforms the points in the 3D model (in meters) into the points in the image (pixels). Each picture can have a different focal lengths, hence the camera intrinsics can change. I'm using OpenCV in C++.
I've found solutions for similar problems but either you already have the camera calibrated, with a fixed focal length (in this case you only need one image) or you don't have the camera calibrated but you consider that its intrinsic doesn't change (in this case you need at least 3 images).
Is there anyway to find the camera position in the 3D model without knowing anything besides the homographies (with different focal lengths)?