An echo sounder is a device to measure the depth of water (or any liquid). An echo sounder sends out sound waves and measures how long it takes for the echo of the sound to come back. The speed of sound in the water is known so that the depth can be calculated. Echo sounders are crucial tools for environmental monitoring and mapping underwater terrain.
The results of depth measurements using an echo sounder or bathymetric survey can be presented in several forms.
Most popular are:
There are multiple different types of devices utilizing echo sounding principle. Single-beam echo sounders (SBES), which may be single-frequency and dual-frequency; multi-beam echo sounders (MBES), scanning sonars, and side-scanning sonars. All these, except SBES, are usually bulky and heavy and not suitable for UAV deployment, at least without a kind of towed buoy. Additionally, the Echo Sounder sensor often incorporates advanced features such as temperature sensor and tilt sensor.
All sensors are manufactured by Korean company EofE Ultrasonics Ltd., specializing in survey-grade sonar products.
It measures the distance till the first “obstacle” in the water - sediments, seaweeds, and even fish. Therefore, if the bottom of the survey area is covered with seaweed, this basic configuration may not work for such a case.
The measured depth will fluctuate erratically depending on what echo sounder received reflected sound - bottom or vegetation. That means that to get “clean” readings from EchoLogger ECT 400S the bottom should be without seaweeds, ensuring a precise depth measurement.
The benefit of EchoLogger ECT 400S is that it has a very short dead zone of 15cm - a minimum distance it can measure. That makes the system with ECT 400S suitable for very shallow surveys, starting from approximately 30cm deep.
Technically, a dual-frequency echo sounder is two devices with different acoustic frequencies, combined in one compact housing.
The higher frequency is 450 kHz, and it will give measurements till the first surface or obstacle. The lower frequency is 200 kHz, and sound with that frequency will pass through seaweeds/vegetation on the bottom, and the device will report clean readings of the bottom.
Note: the dead zone for 200 kHz is 0.5m, limiting the minimum practical survey depth for
that device by approx 0.8m.
EchoLogger ECT D24S is a dual-frequency sounder with tilt and temperature sensor.
Fig.1 -The graph demonstrates the technology: the red line reflects 450 kHz sound, fluctuating between seaweed and the bottom, while the green line (200 kHz) provides steady depth measurements
200 kHz sound impulses will reflect from the top surface of the bottom, but 50 kHz sound can penetrate through organic or light sediments, measuring the depth till the hard bottom.
That creates the possibility of mapping the depth and measuring the thickness and amount of sediments in the water body.
Note: the dead zone for 50 kHz is 1m, and the minimum practical survey depth will be around 1.2m.
EchoLogger ECT D052S is a dual-frequency echo sounder with tilt and temperature sensor.
And we will help you choose the best option
The echo sounder is the standard measurement tool for bathymetry (depth measurement). Usually, the survey process involves using a ship, boat, or unmanned surface vehicle (USV) as a platform for the sensor.
Sometimes, the use of a boat can be complicated, especially in small or hard-to-reach rivers and lakes. The use of USVs is not feasible in every situation because of underwater features. Firstly, it is necessary to have a good point of entry to the water for deployment and recovery. Secondly, using USVs in shallow lakes with lots of seaweed may be impossible. Last but not least, in many cases, a USV should be big enough to resist waves if water analysis is conducted in water in oceans, and a large vehicle may be necessary to transport it.
A drone is compact and easy to transport and deploy. Drones also have a high precision of following planned survey lines and can be used anywhere where there is at least a small area for take-off and landing near the surveyed water surface.
The UAV system is ideal for hard-to-reach locations (steep coasts, mining pits, shallow waters, terrain obstacles), as well as waters of ponds, lakes, and canals. There is no need for an entry point to the water for deployment and recovery. There are applications where the surveyed area was a few hundred meters from the take-off location.
For small water bodies or survey areas, the mobilization cost for the boat or USV with bathymetric equipment may exceed the survey's price. Highly portable UAV system saves time for mobilization and deployment and may be up to 2 times more cost-efficient than a standard approach using a ship, a boat, or a USV.
The system works in a hazardous environment, which humans cannot approach freely. A drone operates without water contact. Therefore, lakes and rivers with strong currents, as well as contaminated waters, become measurable.
The drone's precise positioning while following the survey routes and ability to fly at a constant speed and specified low altitudes result in high-accuracy measurements.
Physically, disregarding of applications, echo sounders will measure the same. However, applications may dictate survey planning, data processing, and final reporting differences. Below is the list of typical applications for the drone-borne echo sounder systems:
And we will help you select the appropriate echo sounder for your application
The echo sounder system for UAV consists of multiple components. For your convenience, all necessary components, software, and services are combined into echo sounder bundles.
Compatible drones: DJI M300/M350/M600, Inspired Flight IF1200A, Harris Aerial H6, and Wispr Ranger Pro and similar UAV
Fig.2 - Image representing the correlation between drone-mounted system with echo sounder and measurement pole with Trimble RTK GNSS receiver (in red circles)
In bathymetry, traditionally dominated by boats, there is a growing presence of UAV-based solutions incorporating echo sounders for bathymetric data collection. That raises the normal questions about the accuracy of the system.
As the UAV-borne system uses survey-grade echo sounders and hi-end RTK GNSS receivers of the modern drones for the positioning, the accuracy of the data collected using drone-mounted systems is the same as for manned and unmanned boats.
Our customers compared data collected using drones with more traditional methods. The image (see Fig.2) is a track of the data from the drone collected using a measurement pole with Trimble RTK GNSS receiver (in red circles), data courtesy of Geopartner Landinspektorer A/S. That method of measurement is considered to be the most precise. It is visible that the difference is negligible.
The echo sounder system records data in three standard formats:
Discover the data sets for all three standard types of drone based echosounders by SPH Engineering.
