Overview
The Surveyor 240-16 is an affordable MBES (Multibeam echosounder) with excellent performance/price. Its primary function is bathymetry. It's small and light enough to be carried by even very small uncrewed vessels.
Acoustics
The unit operates at 240khz and features a 16-element receive array. An angle-of-arrival estimation algorithm is used to detect the position of specific acoustic reflectors well in excess of the accuracy achievable with conventional beam-forming techniques. It has a horizontal field of view (cross-track beam width) of 80° and an along-track beam width of 4°. Although the effective cross-track beam width with conventional beam forming would be about 7 degrees, Surveyor can resolve angle of arrival to less than one degree.
Performance
In most situations, points can be detected up to 50m (slant range) away from the sensor. In ideal conditions this can be substantially further. A variety of environmental factors can reduce the ability to detect points (target hardness, sensor pitch/roll, acoustic interference, etc..). Even in compromised conditions, you can expect reliable performance up to 30m from the target plane.
20hz is the maximum ping rate at close range (about 20m). As the range increases, the ping rate must reduce due to the speed of sound.
10-20 points can be detected in each ping. Point density can be increased by slowing the vessel, or performing multiple overlapping passes.
Sensors
Surveyor features a built-in 9 axis IMU. SonarView uses the internal IMU for pitch and roll compensation and combines this with position and heading information from a moving platform (such as a USV or towfish) to accurately place each data point in the correct geographic location.
Housing
The aluminum housing is rated for 300m depth and features an external status LED. Mounting holes have been placed on the top, bottom, and sides (M4 - 0.7mm). The housing can be opened for inspection or servicing, it is not potted or oil-filled. Because some small ROVs are limited by the number of cable penetrations, we've placed an auxiliary M10 penetrator hole on the Surveyor's housing. This can be used to relocate an i2c sensor from the vehicle's hull (such as the Bar pressure sensors on the BlueROV2).
Connections
The unit operates on 10-30V DC. It consumes approximately 5w at idle and up to 15w while pinging. Ethernet is used for communications though a 4 position JST-GH connector (Blue Robotics Connector Standard). An RJ-45 adapter is provided.
Data Formats
We are working with various hydrographic software suppliers on additional integrated support, and we are interested in working with more!
Requirements for Successful Operation
Accurate position and heading data from your vessel
Surveyor relies on an external source for heading and positioning data. Ideally this data should be available at 20hz or greater (or at least greater than Surveyor's ping rate). The accuracy of the detected points will be directly effected by errors in these sources.
Supported sources: mavlink2rest, NMEA
SonarView
The unit has no onboard datalogging. A computer running SonarView must be connected to operate the sonar and log data. This could be a Windows/Mac/Linux computer, or a companion computer like a Raspberry Pi.
Surveyor datalogs can become quite large, budget 5GB per hour at 20hz ping rate. If using a Raspberry Pi, 128GB is a good size.
A stable platform
Although we compensate for pitch and roll to position points in 3D space, better results can be achieved with a more stable platform (just like a camera).
Thoughtful mounting
Avoid mounting the transducer in an area near air bubbles, excessive turbulence, or other potential sources of interference.
3D View:
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