One of the great things that we can do on our drones is activate captions, which if the captured video is played on an app like VLC or Drone Viewer is can show altitude as the flight progresses. However it's displayed in MSL rather than AGL, so if you want to know what the AGL is you have to know the MSL from where you launch and do some subtraction. That's all well and good, and the MSL from launch point can be found in Google Earth Pro. But what if you wanted to know right there and then as you launch? Is there an app for the phone or a way to easily determine the MSL where you might be standing at any given moment?