Elevation Changes Between Two Surfaces

Skyveyor1

Hello, 

I am trying to compare SRTM data to a user created surface. The user created surface is georeferenced with survey grade coordinates. I use SRTM data to fly a constant altitude above the terrain. I want to determine how accurate the SRTM data is in my area. I tried using compare two layers, which is close to what I want, but not quite. I'd like to see the elevation difference between the two surfaces. 

Any help is appreciated. 

Thanks, 

Skyveyor

946

Skyveyor1

Thank you.