Drone and cart GPR compared for river ice and bathymetry profiling

The challenge

Ice jams on rivers can cause floods, and flood models need ice thickness data. Walking on river ice with equipment is risky, and ice jams are unstable. The team wanted to know if airborne GPR could give reliable ice thickness and reach areas where a cart survey would be unsafe.

Snow depth also matters. On test day the snow was shallow, about 5–10 cm, so the cart worked well. With much deeper snow, the drone would avoid the need to clear paths. Flying close to the ice needed constant watching: an operator walked alongside so the drone did not drift into trees on the banks.

The solution

The team surveyed matching lines across the river two ways:

• Drone GPR. A DJI M300 RTK carried SPH Engineering's 500 MHz GPR integrated system on low passes at 0.75 m and 1.0 m above the ice. RTK kept the paths repeatable and covered the full river width.
• Cart GPR. The same antenna on a hand-pulled buggy, in direct contact with the ice, as a baseline.

For reference, 25 holes were drilled with GNSS position and water depth recorded at each. A shallow-water ice profiler installed before freeze-up also logged ice thickness and water level at one point all winter.

Data processing

Drone flight paths were split into profiles in GeoHammer Pro, then both datasets were processed in Prism and Geolitix with the same steps: time-dependent gain, GPS interpolation, bandpass and horizontal filters, and background removal. Average ice thickness from the boreholes was used to calibrate the radar velocity, and the ice-water boundary was picked trace by trace. Grids were then mapped in QGIS over an orthophoto.

The results

• Ice thickness was largely consistent between drone and cart data.
• Ice was thicker near the banks, where water flows more slowly.
• Cart data is generally more reliable because the antenna touches the surface, but the drone was faster and safer and still gave dependable results.
• The GPR data was detailed enough to also produce a riverbed depth grid in Geolitix.

SPH Engineering recommends drilling several boreholes for either method, so the radar can be calibrated against known ice thickness.

Where this applies in India

The same drone-plus-cart approach suits shallow freshwater and ice work where access is risky:

• frozen lakes and rivers in high-altitude regions;
• glacier, snow and hydrology research at universities and institutes;
• shallow riverbed and canal profiling where boats are impractical;
• flood-risk studies that need repeatable cross-sections.

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

The equipment, available from HobiTech

Ground penetrating radar	SPH Engineering 500 MHz GPR integrated system. Our current 500 MHz drone GPR is the RadSys Zond Aero 500.
Cart	The same antenna was pulled on a buggy. See our GPR cart for terrestrial surveys for Zond GPR systems.
Onboard computer	Not named in the case study. We supply SPH Engineering drone GPR systems with SkyHub by SPH Engineering and the SkyHub GPR software.
Drone	DJI M300 RTK was used in this project. Ask us for current compatible drones.
Processing	GeoHammer Pro, Prism, Geolitix and QGIS

Case study by SPH Engineering, published August 2025. This page summarises it in our own words; the research was carried out by Université de Sherbrooke, not by HobiTech. Read the original case study on SPH Engineering ↗