Color coded elevation map

I am trying to understand what is the vertical datum used in the elevation maps. When the color code shows -5.8 feet, from what point is that measured?

Luis Martinez September 02, 2015 17:59

Official comment

Luis,
DJI's cameras record the altitude relative to the takeoff point. If you are flying at 100 m, it records that value in the EXIF geotags and that is all Maps Made Easy has to go on without there being additional information provided in either the basemap or manual GCP workflows. If you take a picture on the ground before or after taking off, you can upload this image with the rest of your pictures. We will detect that this is the ground image, look the elevation of this point up with USGS and add that as an offset to the processed result. This is why it is important not to take off from the top of a building or in a hole at a construction site, the USGS elevation lookup value won't match. Our Map Pilot app automatically records this image when it lands after a successful mission.

Tudor September 02, 2015 19:03

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5 comments

ok, If I didn't take a photo on the ground before take off, then the color code graph is not correct?

Luis Martinez September 02, 2015 19:09 0 votes

If you don't have that offset image included at the time of upload, all just made with DJI cameras will be a relative elevation map only. The color code is right, you just have to refer to the elevation legend at the bottom. The elevation values are also available in the DJI with 32-bit float precision.

Tudor September 02, 2015 19:20 0 votes

Perhaps I asked the wrong question...when the elevation legend at the bottom showsa color to be -5.8 feet, what is the zero datum if I did not take a picture on the ground before or after taking off?

Luis Martinez September 02, 2015 21:41 0 votes

Luis,
Yes. Without having anywhere to tie the elevation to, the elevation map is just a relative one and sometimes the numbers go negative depending on where the takeoff point was in relation to the rest of the terrain.

Tudor September 03, 2015 18:35 0 votes