Analysis of in-transit range projection errors

1. If the ground is folded along the waypoint ray, there may be more than one surface point that lies along the ray. We could check for there being more than one possible range point along the ray in our current FOV, but this check is not reliable, since we might fail to get range data for the actual waypoint due to stereo matching limitations, or because the actual waypoint is not in our FOV at all.
2. If the ground is folded along our line of sight, then we might judge an intervening obstacle as being sufficiently close to the waypoint ray. Our ability to discriminate this case depends on the accuracy of the relative position estimate between the waypoint base and our current location.