Echo Sounder / Sonar
An echo sounder measures water depth by timing an acoustic pulse from a transducer to the bed and back. Paired with GNSS positioning it produces a bathymetric survey - a contoured map of the bed used for dredging volumes, reservoir capacity, bridge foundations and navigation channels.
Mapping the ground you cannot walk on - river beds, reservoirs, backwaters and harbour channels.
ALSO CALLED: sonar · single beam echo sounder · bathymetric survey equipment · depth sounder · hydrographic survey instrument · river bed survey
To confirm: whether echo sounders are held in stock, supplied to order, or delivered through a partner
Typical specifications
Class-level figures. Individual models vary, so treat these as the range to check a quotation against rather than a guarantee.
- What it measures
- Water depth below the transducer, logged against GNSS position
- Typical depth accuracy
- Centimetre-level in shallow water; degrades with depth and sediment
- Single beam vs multibeam
- Single beam gives a line of soundings; multibeam gives full coverage
- Typical operating frequency
- 200 kHz shallow work; lower frequencies for greater depth
- Required alongside
- GNSS positioning, heave/tide correction, sound velocity data
- Common output
- Sounding file, bed DEM, depth contours, dredge volume report
How a echo sounder / sonar works
01
Transmit a pulse
A hull- or pole-mounted transducer emits a short acoustic pulse directed at the bed.
02
Time the return
The echo's travel time, multiplied by the speed of sound in that water, gives depth. Sound velocity varies with temperature and salinity, so it is measured rather than assumed.
03
Position every sounding
A GNSS receiver timestamps each sounding with a coordinate, turning a depth reading into a mapped point.
04
Correct for water level
Depths are reduced to a datum using tide or reservoir level records, so surveys from different days are comparable.
05
Build the surface
Soundings are gridded into a bed model, from which contours, cross-sections and dredge or storage volumes are computed.
What it is used for
- River and canal bed profiling
- Reservoir and dam capacity surveys
- Siltation and sedimentation monitoring
- Dredging volume computation
- Bridge and jetty foundation surveys
- Backwater and harbour channel mapping
- Pre- and post-monsoon scour assessment
Who uses it
- Irrigation and water resources departments
- Port and harbour authorities
- Dredging contractors
- Bridge and marine consultants
- Environmental monitoring agencies
How to choose a echo sounder / sonar
Single beam or multibeam
Single beam is far cheaper and adequate for cross-sections and reservoir capacity. Multibeam gives full bed coverage and is what dredge acceptance and navigation charting need.
Frequency versus depth
High frequency resolves detail in shallow water; lower frequency reaches deeper but blurs. Kerala's rivers and backwaters are mostly shallow-water, high-frequency work.
Positioning integration
The sounder is only half the system. How cleanly it timestamps and integrates with your GNSS decides whether the survey processes in an afternoon or a week.
Vessel and mounting
Transducer mounting rigidity and offset measurement matter as much as the instrument. A poorly measured offset biases every sounding in the survey by the same amount.
What it costs
Bathymetric work is usually quoted per kilometre of river, per water body or per survey day, and vessel hire and access are often the largest line items rather than the instrument. To confirm: bathymetric survey rate bands
Echo Sounder / Sonar vs the alternatives
Echo Sounder / Sonar vs Drone / LiDAR survey
Aerial methods stop at the waterline - neither camera nor standard LiDAR sees usefully through turbid water. A combined survey maps banks from the air and the bed by sonar, then merges the two surfaces.
Read about drone / lidar surveyWhat Axisline does with a echo sounder / sonar
FAQ
Echo Sounder / Sonar - common questions
What is a bathymetric survey?
A bathymetric survey maps the shape of a water body's bed. Depths measured by echo sounder are combined with GNSS positions and corrected to a datum, producing depth contours and a 3D bed model. It is the underwater equivalent of a topographic survey and is used for dredging, storage capacity and foundation design.
How accurate is echo sounder depth measurement?
Centimetre-level accuracy is achievable in shallow, calm water when sound velocity is measured and water level corrections are applied. Accuracy degrades with depth, wave motion, soft or gassy sediment, and any error in the transducer offset - which is usually the largest practical source of bias.
What is the difference between single beam and multibeam?
A single beam echo sounder measures one depth directly below the vessel, producing lines of soundings along the tracks you run. A multibeam sweeps a fan across the bed and gives complete coverage between tracks. Multibeam costs considerably more and is used where full bed coverage is contractually required.
Can you survey Kerala's backwaters and reservoirs?
Bathymetric survey of rivers, canals, reservoirs and backwaters is within the scope of geospatial survey work, combining sonar depth measurement with GNSS positioning and shoreline capture. Availability of hydrographic equipment for a specific project should be confirmed at enquiry stage. To confirm: in-house echo sounder availability or partner arrangement
Related instruments
Need a echo sounder / sonar - or the survey it produces?
Supply, calibration and service across Kerala and pan-India, with field crews covering all 14 districts.