Short answer: A single-beam echo sounder measures one depth straight below the drone along each line. It is light, simple and enough for most reservoir, pond and river surveys in India. A multibeam echo sounder such as SPH Engineering's EchoNIMBUS-MBES measures a fan of depths across each line, so it builds a full 3D model of the bed. It is heavier, needs specialist processing software and costs more. Choose by the output you need, not by the water body.
Last updated: 24 October 2026.
Key takeaways
- Single-beam: one depth per ping, straight down. The EchoLogger sounders weigh 275–460 g and have a nominal accuracy of 0.2% of depth.
- Multibeam: a swath of depths across each line. The EchoNIMBUS-MBES has an 80° cross-track swath, 16 receive elements and a 0.5–50 m range.
- Single-beam data is processed in Hydromagic; multibeam data in BeamworX.
- Side-scan sonar (EchoNIMBUS-SSS) is a third option: it makes an image of the bottom, not depth numbers.
- Both fly on a DJI M350/M300 RTK class drone with the SkyHub onboard computer, a radar altimeter and UgCS.
Drone bathymetry has become a practical way to measure reservoirs, tailings ponds, canals and rivers without putting a boat or a crew on the water. The first decision a buyer faces is the type of echo sounder. Here is how single-beam and multibeam compare, using the specifications SPH Engineering and the makers publish.
How each one works
Single-beam. The echo sounder hangs on a rope below the drone, with the transducer in the water. Each ping returns one depth directly beneath it. The drone tows the sensor slowly along planned lines (0.5–0.7 m/s for the EchoLogger systems), or stops at waypoints where weed makes continuous towing impossible. Logging starts automatically when the sensor is submerged. The depth map is built by interpolating between the lines.
Multibeam. The EchoNIMBUS-MBES uses a Cerulean Surveyor 240-16 sonar on a foldable mount. It sends a fan-shaped beam, 80° wide across the flight line, and its 16 receive elements resolve many depths in that fan on every ping. Instead of one line of points you get a strip of dense coverage, and the strips join into a 3D point cloud of the bed.
Side by side
| Single-beam (EchoLogger) | Multibeam (EchoNIMBUS-MBES) | |
|---|---|---|
| What you get | One depth per ping along each line | A swath of depths across each line (3D point cloud) |
| Frequency | 50/200 kHz (ECT D052S), 200/450 kHz (ECT D24S), 450 kHz (ECT 400S) | 240 kHz |
| Depth range | From 0.15 m up to 200 m, depending on model and frequency | 0.5–50 m |
| Accuracy / resolution | Nominal 0.2% of depth, resolution under 1 mm | Range resolution 0.5% of the range setting; 1° angular resolution |
| Sensor weight | 275 g (ECT 400S) to 460 g (ECT D052S) | 1.8 kg with mount; 2.4 kg for all components |
| Deployment | On a rope below the drone, towed slowly | On a foldable mount under the drone |
| Processing software | Hydromagic Survey | BeamworX Suite (AutoPatch, AutoClean) |
| Best for | Volumes, siltation checks, depth contours, regular monitoring | Detailed bed models, structures, sediment volumes, erosion |
Specifications from SPH Engineering, EchoLogger and Cerulean. Range is measured from the transducer; the practical minimum depth for single-beam sounders is about 15 cm deeper, because the sensor must be submerged.
When single-beam is the right choice
- Reservoir capacity and siltation. Lines spaced evenly across the water give a reliable depth model for volume and silt calculations. The ECT D052S adds a 50 kHz channel that reaches deeper and handles soft sediment better.
- Ponds, canals and small lakes. The lighter ECT 400S and ECT D24S cover shallow, clear water with little set-up.
- Acidic mine water. The ETF 400S has every exposed part in PTFE, for low-pH water.
- Repeat monitoring on a budget. A single-beam system is the simpler, lighter and less expensive kit to own and fly every month.
When multibeam is worth it
- You need the shape of the bed, not just contours. Intake structures, bridge piers, scour holes and dredged channels show up properly only in dense 3D data.
- Sediment and erosion volumes. Repeat multibeam surveys compare surfaces directly instead of interpolated grids.
- Hard-to-reach water where a survey boat costs too much. SPH positions the EchoNIMBUS-MBES for tailings ponds, stormwater basins, small reservoirs and coastal sites.
Multibeam needs calm conditions: SPH says it works best on still and slow-moving water, and fast rivers are surveyed with a zig-zag flight pattern. It also needs a processing step that single-beam does not, a patch test to calibrate mounting angles, which BeamworX AutoPatch automates.
What about side-scan sonar?
A side-scan sonar answers a different question: what is lying on the bottom. The EchoNIMBUS-SSS carries two Omniscan 450SS transducers, one on each side, with a range of up to 150 m, and builds an acoustic image of the bed. Teams use it for search and recovery, pipelines, wrecks and debris. If you need depth figures, pair it with an echo sounder or choose one of the depth systems above.
What else a drone bathymetry system needs
The sounder is one part. SPH Engineering's set-up adds the SkyHub onboard computer (with the echo sounder package for single-beam), a radar altimeter so the drone holds its height over water, and UgCS for planning the survey lines. SPH notes that a standard drone's barometric altimeter can drift by several metres in one flight, while the radar altimeter keeps drift to about 10 cm. Our drone bathymetry guide lists every component and the case studies behind them.
Sources: product specifications published by SPH Engineering, EchoLogger (EofE Ultrasonics), Cerulean Sonar, Eye4Software and BeamworX, as listed on each HobiTech product page.
Frequently asked questions
Is multibeam more accurate than single-beam?
Not necessarily per point. The EchoLogger single-beam sounders have a nominal accuracy of 0.2% of depth. Multibeam gives far denser coverage, so the bed between your survey lines is measured rather than interpolated.
How shallow can a drone echo sounder measure?
The 450 kHz EchoLogger models measure from 0.15 m below the transducer, and the EchoNIMBUS-MBES from 0.5 m. Because the single-beam sensor must be submerged, the practical minimum water depth is about 15 cm deeper than the listed range.
Which software processes drone bathymetry data?
SPH Engineering names Hydromagic Survey for single-beam data and BeamworX for EchoNIMBUS-MBES multibeam data. Results can also be viewed in SPH's DroneGIS.
Which drone carries a drone echo sounder?
SPH lists the DJI M350 RTK and M300 RTK, Pixhawk-based drones and, for the EchoNIMBUS payloads, the DJI M400. Tell us your drone and we will confirm the mount.
Can I start with single-beam and add multibeam later?
Yes. Both run on the same SkyHub onboard computer and UgCS, so the drone, altimeter and planning software carry over.
How much does a drone bathymetry system cost in India?
It is quoted per configuration, because the sounder, mount, software and training differ by job. Ask us with your survey details.
Not sure which suits your site? Tell us the water body and its likely depth, and we will suggest a configuration.
