The disparity dzx depends on the height to the object which is of interest. Disparity dzy depends on camera alignment and camera synchronization. In a calibrated system this disparity should be zero, which means that the search area in the right image can be limited. Disparity (dx,dy) is the measurement of
traveled distance.
Images with different heights in the same matching window are expected in a field environment. Stereo matching of a region will average the heights over that region. The same region is then used for matching distance, as shown in Fig. 4. This means that the height is the same for both matches. Therefore is the distance traveled is height independent.
From (1) the height can be calculated as: