What you need for that is a LIDAR with &quot;first and last&quot;.  You want both the first return and the last return.  Dust, rain, snow, and fog will produce noisy early returns, and solid terrain will produce the last return.  You can also range-gate, ignoring returns out to a certain distance, and move the range gate in and out until you sense something solid.<p>LIDAR can be used to see through fog, snow, and dust to a limited extent.[1][2][3] Better than human vision or cameras.<p>[1] <a href="http:&#x2F;&#x2F;viodi.com&#x2F;2015&#x2F;02&#x2F;17&#x2F;better-eyesight-than-humans-the-advent-of-low-cost-lidar&#x2F;" rel="nofollow">http:&#x2F;&#x2F;viodi.com&#x2F;2015&#x2F;02&#x2F;17&#x2F;better-eyesight-than-humans-the-...</a> 
[2] <a href="http:&#x2F;&#x2F;mil-embedded.com&#x2F;articles&#x2F;case-helicopter-pilots-clear-line-sight-brownouts&#x2F;" rel="nofollow">http:&#x2F;&#x2F;mil-embedded.com&#x2F;articles&#x2F;case-helicopter-pilots-clea...</a>
[3] <a href="http:&#x2F;&#x2F;www.laseroptronix.se&#x2F;gated&#x2F;Rangegatedcameras.pdf" rel="nofollow">http:&#x2F;&#x2F;www.laseroptronix.se&#x2F;gated&#x2F;Rangegatedcameras.pdf</a>