title: How to improve accuracy of camera extrinsics calibration
body: <p>I have a multi-camera system where the field of views are mostly non-overlapping. I have been researching on methods to calibrate the camera extrinsics and the first thing I'm going to try is to take a picture of a chessboard at a known location and use <a href="https://docs.opencv.org/4.5.2/d9/d0c/group__calib3d.html#ga549c2075fac14829ff4a58bc931c033d" rel="nofollow noreferrer">solvePnP</a> from OpenCV to find the extrinsic rotation and translation vectors for each camera separately (following the method described in the answer <a href="https://stackoverflow.com/questions/55220229/extrinsic-matrix-computation-with-opencv">here</a>).</p>
  <p>My problem is, this method uses only one measurement and as every measurement it is prone to errors. I assume that by taking multiple measurements, either by changing the position or the orientation of the chessboard, the accuracy can be improved. But what would be the best way to combine the rotation and translation obtained from the different measurements? A simple average?</p>
  <p>In theory I would think that an option could be using solvePnP on all the points at the same time. Since I am calculating extrinsics the camera can't be moved so I would have to change to position and/or orientation of the board for each picture and measure the 3D points positions as accurately as possible each time.</p>
  <p>I'm also wondering if using two chessboards in the same picture would be a possible solution, even if OpenCV doesn't seem to support multiple chessboard detection.</p>
  <p>Is there a better way to measure extrinsics or anything that I'm missing?</p>