Case study by SPH Engineering · Bathymetry · Research
Testing a drone echo sounder against a drained pond
Mississippi State University's Delta Research and Extension Center (DREC) flew an SPH Engineering echo sounder drone over a research pond, then drained the pond and scanned its bed with LiDAR. Comparing more than 11,000 depth points showed how accurate the drone data was and which flight settings work best.
The challenge
Depth maps of inland water support sediment tracking, reservoir capacity checks and flood risk models. Shallow water bodies bring their own problems:
- boat surveys are hard and risky in shallow or remote water;
- echo sounders record depth only along the flight lines, so the gaps between lines must be filled during processing;
- drone depth data had not been thoroughly compared with ground-truth measurements;
- there was little testing of how line spacing and sampling interval affect results.
The solution
The team flew a DJI M300 RTK with an SPH Engineering ECT D052S dual-frequency echo sounder (50/200 kHz), planned in UgCS. The drone flew parallel lines 5 m apart with the echo sounder below the water surface. A radar altimeter and SkyHub held a constant height, and the data was watched live in the UgCS Custom Payload Monitor (CPM) application.
After the survey the pond was drained. The exposed bed was scanned with high-resolution LiDAR, and a GNSS rover measured the remaining puddles.
The results
- Full dataset of 11,439 points: RMSE of ±10.2 cm and R² of 72.8%.
- Filtered dataset (95.45% of points, outliers removed): RMSE of ±6.6 cm and R² of 86.6%.
- Most outliers were in the shallowest zones. The system did better in deeper water.
- Of ten interpolation methods tested, Topo to Raster worked best: ±6.3 cm and an 83% match at 5 m line spacing, and ±7.1 cm and 81.5% at 10 m.
- Flight lines and sampling intervals of 5–10 m gave the best balance of quality and effort. Spacing wider than 20 m raised the error and lowered the correlation.
Where this applies in India
The study gives practical flight settings for shallow-water surveys such as:
- irrigation tanks and farm ponds that need sediment and capacity checks;
- small reservoirs and lakes used for water supply;
- shallow water bodies included in flood studies;
- agricultural universities and research institutes validating drone methods.
SPH Engineering's bathymetry training is also available through HobiTech.
The equipment, available from HobiTech
| Echo sounder | EchoLogger ECT D052S |
| Onboard computer | SkyHub by SPH Engineering with the SkyHub echo sounder software. A radar altimeter held the flying height. |
| Flight planning | UgCS - Drone Flight Planning Software, with the UgCS Custom Payload Monitor for live data |
| Drone | DJI M300 RTK was used in this study. Ask us for current compatible drones. |
Case study by SPH Engineering, published June 2025. This page summarises it in our own words; the research was carried out by Mississippi State University's Delta Research and Extension Center, not by HobiTech. Read the original case study on SPH Engineering ↗
Need accurate depth maps of shallow water?
Send us the water body size, depth range and accuracy you need. We will specify the drone, echo sounder, SkyHub and UgCS setup, quoted in rupees with a GST invoice.