Edge's depth map precision


The depth map ( depth_map/image ) precision us quite good at the center of the image (~1cm @ 1m with a 128 nb disparity). However on the edges, I have an error ~30cm with the same characteristics. (which corresponds to a disparity error of ~20px). is this a calibration problem ? Or something else ?

What is the camera resolution corresponding to the camera calibration files stored in the slamdunk ?