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Strange elevations on latest map (March 11,18).

the elevation layer shows

elevations -671 -585 -499 -327 -241 -155  -69.6 16.3 102.3 145.2 188.2

what could I have done that would cause below sea level elevations in Texas.


Official comment


Ground Reference images actually were uploaded and were successfully applied. The flight was at 50m and the offset for the area was 246m.  

The elevations were thrown off because there were a few things in the scene that caused some pretty big issues.

The pond had some really hard southern sun reflections in it and the entire area around it that had any picture of the pond were very higher error.

Also, it was a terrain aware flight that was flying pretty low at about 50 meters Then there is a large highly reflective roof building that is at least 20 meters tall in areas. Our data collection guidelines say to fly AT LEAST 4 to 5X as high as the tallest thing the survey area. Being a terrain aware flight the ground was hugged pretty tightly and the aircraft flew pretty close to the top of that structure which caused another very high error area due to the low flight and roof reflections. 

Reflections can be handled or at least made less severe by using a circular polarizing filter. 

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In my post about strange elevations, I was flying a Phantom 4 Pro map settings 80% overlap at 194’ altitude 

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