Autonomous survey boat for depth and water-quality mapping: student parts list

A boat that runs survey lines across a lake on its own and logs water depth and temperature against GPS position. It is one of the most useful final-year projects there is, because the map it makes is a real result that someone can use.

What the boat does

• Follows survey lines on its own, planned on a laptop and flown by ArduPilot Rover, the same software that flies drones, set up for a boat.
• Measures depth under the hull with an echo sounder, logged with the GPS position, which gives you a bathymetric map.
• Measures water temperature, and whatever water-quality probes the project adds: pH, dissolved oxygen, conductivity or turbidity.
• Comes back by itself when the battery runs low or a radio link drops, and never leaves the area you have drawn round the lake.

Indian research groups have published boats like this for river and lake monitoring. The IIT Kanpur team's open-source design in HardwareX is worth reading before you start.

Hull and propulsion

Hull. A catamaran is the easy choice: two hulls about 1 to 1.5 m long with aluminium crossbars between them. It is stable, it leaves a clear space in the middle for the echo sounder, and the two hulls are an obvious place for two thrusters. PVC pipe with sealed end caps, foam or a pair of model-boat hulls all work.

Steering. Put one thruster on each hull and steer by running them at different speeds, like a tank. There is no rudder to build, and the boat can turn on the spot at the end of each survey line. ArduPilot Rover calls this skid steering.

Thrusters. The list uses Blu-Sub's [Z60E](/products/blu-thrust-z60e-500). Blu-Sub rates it at 4 kgf forward at 24 V and 290 W at most, and it has its speed controller built in, so each thruster needs only power and a signal wire. A survey boat under about 15 kg moving at 1 m/s needs a small fraction of that. Blu-Sub sells a weed guard for the Z60E, and it is worth fitting: weed fouls propellers in most Indian lakes. Order one clockwise and one counter-clockwise, so the torques balance.

Blue Robotics' [M200 motor](/products/m200-motor-standard-1-meter-cable-length) with the [Basic ESC 500](/products/basic-esc-500-standard) is the surface-vessel propulsion Blue Robotics uses on its own BlueBoat. It costs more per side, but the BlueBoat's documentation comes with it.

Power and endurance

Run it on a 6S Li-ion pack, which suits the thrusters and holds a lot of energy for its weight. A 6S2P pack of twelve 21700 cells holds about 194 Wh. Say the electronics and echo sounder draw 6 W and the two thrusters about 60 W between them at survey speed. That load, 66 W, is an assumption: measure yours on the first test run. Using 80% of the pack, 155 Wh ÷ 66 W is about 2 hours 20 minutes, or roughly 8 km of survey line at 1 m/s.

That is enough for a pond of 100 × 200 m surveyed on lines 5 m apart: 20 lines of 200 m, 4 km in all, about 70 minutes at 1 m/s. It leaves half the pack for getting there and back, and for the second run you will want once you have seen the first map.

Autopilot and wiring

The autopilot is a [Pixhawk 6C](/products/pixhawk-6c-plastic) running ArduPilot Rover with the frame class set to Boat. Set the left thruster's output to ThrottleLeft (SERVO1_FUNCTION = 73) and the right thruster's to ThrottleRight (SERVO3_FUNCTION = 74). Set each output's range so that its centre is the thruster's neutral point, using the figures on the datasheet that comes with the quotation, and check that each one reverses.

Mount the GPS on a mast, well away from the thruster cables and any steel in the frame, because the compass reads their magnetic fields as heading error. The [PM02 V3](/products/pm02-v3-power-module) handles 2S to 12S and 60 A, far more than this boat draws, and powers the autopilot at 5.2 V.

Failsafes. Draw a geofence round the water you are allowed to use, and set RC loss, telemetry loss and low battery to return to launch. Rover's tuning pages cover the speed and turn-rate controllers. Tune them on a calm day before the first survey.

Measuring depth

Blue Robotics' [Ping2](/products/ping2-sonar-altimeter-and-echosounder) is a single-beam echo sounder: 115 kHz, a 25° beam, and a range of up to 100 m. ArduPilot supports it as a downward rangefinder, so every depth reading goes into the log with the boat's position. Afterwards, grid the points in Python or QGIS to draw the depth map.

Three things decide how good the map is:

• The footprint. A 25° beam lights a circle 2 × depth × tan 12.5° = 0.44 × depth across. At 5 m that is about 2.2 m, and the sounder reports the shallowest thing inside it.
• Line spacing. The sounder measures only under the hull, so the spacing of the lines sets how fine the map can be. Closer lines give a better map but take longer to run.
• Speed of sound. The sounder converts echo time to distance at an assumed speed of sound. In fresh water that is about 1,480 m/s at 20 °C and about 1,510 m/s at 30 °C, a 2% difference. On a warm Indian afternoon, that could put a 5 m depth 10 cm out. Log the water temperature and correct the depths afterwards: true depth = measured depth × actual speed ÷ assumed speed.

Mount the transducer below the waterline, in the middle of the catamaran, away from the thrusters' wash, because bubbles hide the bottom.

Temperature and water quality

Blu-Sub's [M10 water temperature sensor](/products/subsea-m10-water-temperature-sensor) uses a TSYS01 element, accurate to ±0.1 °C from −5 to 50 °C, on I2C at address 0x77. Blu-Sub lists it as compatible with Pixhawk autopilots. Mount it through the bottom of a hull or on a bracket, so it sits in the water and out of the sun.

For pH, dissolved oxygen, conductivity or turbidity, use lab-grade probes with their own interface boards. Log them on a Raspberry Pi or a microcontroller that also reads the autopilot's position over MAVLink, so every sample carries a place and a time. The electronics only have to cope with rain and splashes, so an IP67 plastic box with cable glands is enough.

If the survey is the project

If what the project needs is the survey and not the boat, Blue Robotics' [BlueBoat](/products/blueboat-uncrewed-surface-vessel-mariner-blue) is a ready-made survey boat. It runs the same ArduPilot software and takes the same Ping2 with Blue Robotics' integration kit. It costs about three times as much as this build, but it saves months of building and tuning.

Before you launch

Ask whoever manages the water body for permission before your first trial, whether that is the municipal corporation, the irrigation department or the campus estate office. Keep a way to recover the boat, such as a kayak or a long line, and never leave it running unwatched. Confirm which telemetry band you may use before ordering the radios. Our telemetry radio guide covers the choice, and our companion computer guide covers adding a Raspberry Pi.

Sources.

• Skid steering outputs and frame set-up from ArduPilot Rover: motor and servo configuration (accessed 2026-09-23)
• Ping2 frequency, beam width, range and ArduPilot support from Blue Robotics' Ping sonar technical guide and ArduPilot: Blue Robotics Ping sonar (accessed 2026-09-23)
• Thrust and power of the Blu-Thrust Z60E, its weed guard, and the water temperature sensor's accuracy and interface, from Blu-Sub's published specifications.
• Current rating and output of the PM02 V3 from Holybro's product page (accessed 2026-09-23)
• The IIT Kanpur water-monitoring boat: Autonomous water sampling and quality monitoring in remote locations: a novel approach using a remote-controlled boat, HardwareX, 2025.
• Speed of sound in fresh water against temperature from standard tables. The endurance figures are estimates from an assumed load.

Published 23 September 2026. Last revised 25 September 2026. Corrections to sales@vebixautomation.com.

Planning a survey project?

Send us the size of the water body, the depths you expect and the measurements you need. We will check the parts against them and send a quotation your department can raise a purchase order against. Ask for a quote.