Negative obstacles (e.g. potholes) in particular are trouble for line-of-sight flight time sensing modalities like laser & radar. The lower the sensor is mounte

Negative obstacles (e.g. potholes) in particular are trouble for line-of-sight flight time sensing modalities like laser & radar. The lower the sensor is mounted on the vehicle, the longer (in direction of travel) the hole has to be before you get a sufficiently large difference to notice between returns from the same beam in subsequent time-steps. This is of course worsened further by increasing vehicle speed. It is somewhat mitigated by having multiple beams, i.e. the Velodyne laser scanner has 64, but even still only a few are hitting the obstacle and surrounds at any one time. Some of the more interesting research in this area uses infrared to detect the change in heat of a shadowed hole versus flat ground. Of course, that only works when there's sunshine to provide the heat source. P.S. Google people reading this (Urmson, Ferguson, etc), please consider this my annual reminder of the awesomeness of your Google Sydney office and the large quantities of autonomous field robotics engineers training and working within walking distance of it, for wages that could be doubled without your budgets even noticing...