Mapping subsurface layers in a protected reserve with drone GPR

The challenge

Holtingerveld is a protected reserve of heathland, sandy soils and water-retaining layers. In some areas a quad-towed GPR was not allowed because the ground is fragile, and dense vegetation blocked contact with the ground. Carrying antennas by hand gave poor data because their height and angle kept changing. The team also had to show that drone data would match the established ground method.

The solution

In accessible areas, Medusa Explorations used a 300 MHz ground-coupled Zond 12 towed behind a quad. In restricted areas, it flew SPH Engineering's GPR integrated system with a 300 MHz Zond Aero LF antenna under the drone. A radar altimeter gave True Terrain Following, SkyHub held the drone at about 1.5 m above ground, and UgCS was used to plan lines that follow the terrain.

Batteries were swapped mid-survey and the mission resumed from the last waypoint without a break in the data.

The results

• The drone data showed the target layer, interpreted as boulder clay, at depths of up to about 4 m.
• Smaller layers, possibly peat or silt, were also visible.
• The drone data lost a little detail against ground GPR, but not enough to affect interpretation. The profiles were highly comparable.
• Terrain following stayed reliable, and could be paused and resumed within a flight.

Medusa Explorations reported excellent results and sees potential in reserves, peatlands and farmland. For future work it is considering a spotter drone to watch for people or wildlife near the survey area.

Where this applies in India

• wetlands, forests and eco-sensitive zones where vehicles are not allowed;
• farmland with standing crops, where ground equipment causes damage;
• mapping clay, peat or silt layers ahead of canal, embankment or road works;
• geology and soil research where soft or uneven ground stops a cart.

SPH Engineering's GPR training is also available through HobiTech.

The equipment, available from HobiTech

Ground penetrating radar	RadSys Zond Aero LF
Onboard computer	SkyHub by SPH Engineering with the SkyHub GPR software and True Terrain Following (radar altimeter)
Flight planning	UgCS - Drone Flight Planning Software
Ground-based GPR	A 300 MHz Zond 12 towed by a quad was used for comparison. Ask us about ground GPR options.
Drone	The drone model is not named in the case study. Ask us for current compatible drones.

Case study by SPH Engineering, published May 2025. This page summarises it in our own words; the survey was carried out by Medusa Explorations, not by HobiTech. Read the original case study on SPH Engineering ↗