Flying Low

We have talked about the potential need to fly from a higher elevation to a lower elevation using Pixhawk Auto mode.  I have seen the terrain following and absolute altitude discussions but never could I find a discussion on making an auto mission using negative altitudes.  Well that changed today:

I setup two flights starting at 10 m and descending to -10 m at the end of the grid.  It work perfectly!!!  The only changes I made were were to set the Alt Warning in the wp list window to -15 m.  I was losing telemetry (3DR radio) connection on the return legs and I should have raised the antenna.  

Now we need to combine this with a laser altitude unit....