GPR Surveying and Terrain Following

Hi,

I’m looking for a solution for flight planning and using basemaps for terrain following. Are such applications possible with Pixhawk?

I also want to fly very low as I’ll using a GPR attachment which will require this. Is there a lower limit on altitude in the App?

Also, do I need to purchase a hardware unit for the drone to make all of this possible?

Looking forward to a response.

Best,

Niall