In order to get proper measurements I'm trying to do a projection from the 3d points to the 2d camera plane proceeding like this:
- First I'm doing the Camera calibration using opencv and a chessboard, I'm taking a few chessboard shots in different angles and applying the function initUndistortRectifyMap, I´ll have the distortion coefficients, intrinsic and extrinsic parameters.
- With the intrinsic parameters and the coefficients I'll apply lens correction.
- The extrinsic parameters of the previous step are for each chessboard position and I assume that they won't be valid for my particular application, so I'm placing a chessboard in the above marked area as "Measurement Plane" and running again the initUndistortRectifyMap function which this time it's giving me, I think, correct extrinsic parameters of the ROI.
- Once I've got the "correct" intrinsic and extrinsic parameters I´m applying the camera matrix to calculate the 2d points (u,v) projection:
My questions are:
Is it the correct way to proceed for this application?
The camera system only reads X,Y pixel points each time, but to perform a 2d projection seems like I'll need the Z, how could I have this last coordinate of the 3d point?