GeoAcoustics Demonstrates Man-Portable AUV
Sun illuminated bathymetry of a harbor approach, surveyed during a commercial deployment of the Gavia AUV with the GeoSwath sonar. Approx. surveyed area shown in the image is 250m by 1000m. This was part of a commercial survey carried out for Acergy in 2006 in the Caspian Sea.
The Gavia AUV configured for swath bathymetry survey work. Modular units used, from left: propulsion; control and communications (including GPS, Iridium, wireless and acoustic modem); Kearfott INS; RDI DVL; GeoAcoustics GeoSwath; battery pack; nose (with
Dr. Tom Hiller explains the function of the modules to guests prior to mission start in Singapore.
A Northrop N-P3B two seater sea-plane dive bomber that sank (inverted, and missing the floats) in Reykjavik Harbor, Iceland. This was surveyed by the Gavia/GeoSwath on the Friday as part of the pre-demo tests, before the Gavia modules were carried on com
The Gavia AUV (from Hafmynd, Iceland) was fitted with a GeoSwath Plus 500 kHz sonar from GeoAcoustics Ltd, U.K.
The GeoSwath Plus sonar allows wide swath bathymetry and side scan data to be collected from small vessels of opportunity in water depths up to 200 meters beneath the transducers. The vehicle can collect data “up to the beach”, according to Ralf Timm, Singapore office general manager.
The system was designed to meet the need for a wide swath system capable of high productivity surveys in very shallow waters, and can achieve swath widths more than 12 times water depth. The GeoSwath provides high accuracy, high resolution bathymetry (depth measurement accuracy exceeding the latest IHO specifications), and co-registered side-scan data. GeoSwath versions are now also available for mounting on small ROVs and AUVs.
More than 90 people attended the three-day series of demonstrations. They included representatives of regional navies, local and international survey companies, and interested members of the local surveying community.
What they saw was a beach-based launch-collect-recover mission. The Gavia was programmed to run a short survey pattern, collecting GeoSwath sonar data. For this type of mission the modular Gavia base vehicle is fitted with the sonar module, an RD Instruments doppler velocity log (DVL) and a Kearfott inertial navigation system (INS). These are in addition to the Gavia’s standard GPS, Iridium phone, wireless link, obstacle avoidance sonar, pressure depth sensor and mini sound velocity sensor. The 20-centimeter-diameter vehicle is about 2.6 meters long in this configuration.
The GeoSwath Plus wide swath sonar gives high resolution swath bathymetry and co-registered true digital side scan, for making bathymetry maps and geo-referenced side scan images of the survey area. For several years GeoSwath Plus data collected from boat-mount systems has been used in nautical charts produced by the U.K. hydrographic office.
With the positioning and attitude accuracy provided by a DVL-aided Kearfott INS, data from a GeoSwath Gavia mission has the same kind of accuracy and repeatability.
The demonstrations were organized by Ralf Timm of the GeoAcoustic’s Singapore office.
“The whole event went extremely well, and I must thank the CSC for being excellent hosts for this landmark event,” he said. “GeoAcoustics Singapore branch is very pleased to be the exclusive agent for the Gavia vehicle in the Asia Pacific region, and the synergy with the GeoSwath 500 kHz AUV-mounted sonar, produced in the U.K. makes this the perfect match,” he said.
GeoAcoustics Ltd. (Great Yarmouth, U.K.) has been manufacturing marine survey equipment for more than 25 years, specializing in sonar survey equipment for engineering geophysics applications. The principle product lines are swath bathymetry systems for shallow waters, side scan sonars and sub-bottom profilers.
Hafmynd is a developer of novel underwater technologies. Their Gavia range of autonomous underwater vehicles provide solutions to customers undertaking research, surveying, and underwater monitoring tasks.
“We understand the tremendous possibilities opened up by recent technological advances and we have developed the tools making the gathering of accurate underwater data widely available at a fraction of the traditional cost,” said a company representative.
Hafmynd Ltd is the sole owner of the Gavia design and IP rights. Hafmynd controls the development, production and marketing of the Gavia system, which enables the company to act rapidly to market trends and customer requirements. New sensors and devices can thus be integrated in the shortest possible time.
The Gavia AUV has been in development since 1997 and can carry an array of sensors including cameras, side scan sonar, various environmental sensors, and payload modules that can be fitted with custom sensors and can utilize either full inertial systems or acoustic transponder-based systems for navigation.