Multibeam survey with Sonobot 5 in Hemmoor, DE, August 2023
EvoLogics, a high-tech provider of robotic solutions, sensor systems, and underwater data networks, is recognized in the industry for its Sonobot 5 uncrewed surface vehicle. The Sonobot is a well-established product with a remarkable track record in bathymetry, underwater object search, and reconnaissance. In 2023 EvoLogics, driven by a commitment to innovation, further enhanced its capabilities through upgraded hardware.
In April 2023, Ocean Business in Southampton, UK unveiled the EvoLogics Multibeam, a new multibeam echosounder option for the Sonobot 5 platform.
During the summer of 2023, team EvoLogics embarked on a demonstration tour, showcasing the new multibeam to partners and clients. Valuable feedback gathered during this tour informed further upgrades to the integration of the sonar with the vehicle platform.
EvoLogics Multibeam
Unlike single-beam echosounders, the multibeam sonar, featured in the 2023 release, offers superior coverage and 3D mapping. Releasing multiple sound waves concurrently, it efficiently maps extensive underwater areas, drastically reducing survey time.
The key strength of multibeam sonar lies in its capacity to generate higher-resolution imagery. Emitting a fan-shaped array of sound waves, it captures echoes from various angles, facilitating the creation of detailed 3D representations of underwater features.
Multibeam sonar excels in providing enhanced depth accuracy compared to single-beam counterparts. Leveraging advanced algorithms, it compensates for seabed complexities, mitigating the impact of factors like slope, refraction, and interference.
The multibeam sonar for the Sonobot 5 leverages a Norbit OEM solution, an entry-class multibeam sonar with a professional approach. Featuring high-grade dual GNSS and INS positioning and motion control, standard across all Norbit echosounders, this system boasts 256 beams at 1.45°x1°, a range exceeding 200 m, and a 50 Hz ping rate. These specifications enable professional surveying in accordance with the IHO’s S-44 standard.
Sonobot 5 with the updated EvoLogics Multibeam
EvoLogics engineers meticulously integrated the Multibeam with the Sonobot 5 platform
The compact Norbit sonar interface unit (SIU) is fully embedded in the submergeable pod of the Sonobot vehicle. Connected by a single cable for power and data link, the sonar head is easily detachable with a slide-and-lock mechanism for convenient transportation and storage.
In the pursuit of optimal performance, a custom-molded streamlined cover was added to the sonar head before the production of the first serial orders. This streamlined cover not only enhances the hydrodynamics of the vehicle but also adds extra robustness, providing crucial protection to the sonar-pod assembly.
The streamlined cover is particularly advantageous for performing a multibeam sonar survey against a strong current, as it minimizes drag and ensures efficient navigation through challenging conditions. It enables better utilization of the Sonobot’s powerful thrusters and aids in maintaining the steady survey speed during data collection.
The mechanical connection between the submergeable pod and the sonar - the slide-and-lock mechanism - underwent further improvement after the final trial tour, enhancing the overall handling of the unit before and after field operations.
Bathymetry at the mound site taken in 2017 with the Sonobot’s standard 200 Hz single-beam echosounder with the “cairn” clearly visible
Tests at the Plessower Lake “cairn”
In November 2023, EvoLogics completed a survey with the upgraded Sonobot 5 multibeam platform, taking the vehicle to the Plessow Lake in Brandenburg, Germany, a regular testing site for the company since 2016.
Notably, early trials at this site revealed an unexpected feature: a cairn-like mound formation on the lake floor, initially thought to be an ancient burial mound. EvoLogics shared the bathymetric data with the Association for Underwater Archaeology Berlin-Brandenburg for evaluation. Subsequent underwater archaeological prospection determined that the feature was a geological phenomenon, likely a remnant of the last glacial period.
Despite its natural origin, the mound became a focal point for testing bathymetric equipment. EvoLogics consistently returns to Plessow Lake with the Sonobot vehicles to utilize the distinct features of the cairn for assessing echosounders' capabilities in detecting and mapping underwater structures. The mound's elevation and shape create variations in the lake's bathymetry, providing a unique opportunity to evaluate the echosounder performance in measuring depths and generating detailed bathymetric data.
Multibeam sonar survey of the underwater mound, DCT data preview during the mission, November 2023
EvoLogics engineers took the Sonobot 5 with the upgraded multibeam sonar to the Plessow Lake site, capitalizing on the known mound feature and existing single-beam bathymetry data. The survey plan chosen for the multibeam swath survey at the Plessow Lake is a crosshatch pattern, a series of intersecting parallel lines. This pattern ensured comprehensive data collection, eliminating gaps in area coverage.
During the survey, the complete sonar dataset was stored onboard the vehicle, with a live preview displayed to the operator at the land station. EvoLogics Multibeam is compatible with Norbit data collection tools DCT and NORdredge, web-based utilities for real-time monitoring of multibeam sonar operations. Norbit DCT was used for the live multibeam data preview at the Plessow Lake, and even without post-processing of the full set of data points, the multibeam sonar data preview is more detailed than the single-beam bathymetry of the area.
Multibeam sonar survey of the underwater mound, processed with QPS Qimera, November 2023
The superiority of the multibeam sonar system over a single-beam echosounder is evident in projects requiring highly accurate and detailed mapping. EvoLogics is committed to meeting diverse surveying needs by offering compact and easy-to-handle multibeam sonar technology for higher-quality data.
The Sonobot 5 with EvoLogics Multibeam is currently in serial production for customers worldwide, with the team gearing up for upcoming demonstration events to showcase the vehicle and its configurations in 2024.
This article was originally published in the Ocean News and Technology magazine, December 2023 issue.