Bathymetry with drones: it is possible!
In addition to boats, we can also perform bathymetric surveys (measurements of the water bed) using drones. To do this, we suspend an echosounder beneath the drone, which then hangs just in the water to perform measurements. The drone then flies a specific pattern via software.
Technical execution
Naturally, bathymetric surveys are not performed as often with drones, but rather with specially equipped vessels. However, in some cases, it is more efficient to conduct the bed survey with drones:
- when the water is inaccessible to a vessel, or too dangerous
- for smaller streams
- projects with a limited surface area
- shallow waters where a boat cannot be used or is difficult to operate
Additionally, the cost of a drone is generally lower than that of a vessel for performing the surveys.
When performing bathymetric surveys with drones, there are several important factors to consider.
For instance, the drone must remain at a fixed height, making a terrain-following function a requirement. Data shows that a GPS signal alone is not reliable for this, and RTK or, preferably, PPK is required. Otherwise, the drone turns into a submarine.
In addition, we must always take into account the relevant geoid models, reference heights, the distance between the RTK antenna and the echosounder, potential currents, and other factors relevant to the drone flights.
Based on these and other parameters, we can use software to plan a drone flight for the survey so that it proceeds automatically.
bathymetry with drones
The measurable depths depend on the payload—specifically the type of echosounder used under the drone. On average, the range is between 1 and 200 meters, depending on the acoustic frequency.
Factors:
During execution, several factors must be taken into account:
- Water currents: for this, we can use an echosounder with a tilt meter that automatically compensates for the current in the water, and/or the survey can be conducted in a zigzag grid.
- wind and water speed: the permitted speed differences between the water and the wind are limited.
Technical execution
For the processing of the survey, we need to use various software packages.
To do this, we must first export the recorded data from the device and import it into the software.
This can be imported in CSV, NMEA, or SEG-Y data formats.
Following a brief workflow, this data can be processed into elevation maps. In doing so, we must consider reference heights, geoid models, height above the water, and other variable parameters.
processing bathymetric drone flight
Cited examples are the property of ERELIUS, Israel.