GPS Intelligent Buoys
Encyclopedia
GPS intelligent buoy systems may be classified as inverted LBL devices where the transducers are installed on GPS equipped sonobuoys that are either drifting or moored. GIBs may be used in conjunction with an active underwater device (such as a pinger equipped torpedo), or with a passive acoustic sound source (such as an inert bomb striking the surface of the water). Typically the sound source or impact event is tracked or localized using a time of arrival
(TOA) technique. Typically several GIBs are deployed over a given area of operation; with the total number determined by the size of the test area and the accuracy of the results desired. Different methods of GPS positioning may be used for positioning the array of GIBs, with accuracies of cm to meter level in realtime possible.
The system in patent protected and products are manufactured by the French company ACSA-underwater-GPS (subsidiary of the ALCEN group). Three off-the shelf products are available from the small portable GIB-Lite system to the large torpeado tracking GIB-FT, and including the medium-size,medium-range GIB-Plus system.
were created for broad ocean area weapons testing by modifying conventional Navy sonobuoys with small OEM-grade GPS receivers
and deploying them from a helicopter or from P-3 Orion aircraft. The GPS data captured by the GIB was modulated over the analog VHF acoustic data stream using frequency-shift keying
(FSK). This allows the GPS measurement data to be transmitted and received on legacy VHF sonobuoy receiver equipment. A drifting array of twelve or more GIBs would be deployed in a concentric circular array approximately 7 nm in diameter. Weapon strikes within the array emitted acoustic signatures that were captured by the GIBs and transmitted up to the orbiting aircraft. Post-mission the GPS and acoustic data from the GIBs would be combined to determine an absolute coordinate for the impact location in WGS 84 coordinates.
positioning is the TARGT weapon scoring and training system
The system concept (Figure 1) utilizes an array eight to ten GIBs (Figure 2) moored in a 2 km by 2 km array. In the case of the TARGT GIB, the GPS and RF antennas are located on top of the sensor and the hydrophone
, or underwater acoustic transducer
, is located on the bottom. The device is approximately 6 ft tall and weighs 35 lbs.
Inert weapon releases from military aircraft strike the surface of the water within the array, emitting an acoustic signature
that is captured by each of the GIBs. Each GIB determines the precise time of the received signal and transmits this time to the deployment ship in near real time. A command and control system located on the deployment and recovery ship combines the GPS data and acoustic timing information to triangulate the impact location and determine the exact impact time in near realtime. Several methods may be used, the most common being a time difference of arrival (TDOA) least-squares solution algorithm. Post-mission data processing is performed to further refine the results, with two-dimensional positioning accuracies of 1 to 2 meters and impact timing accuracies of 1-2 milliseconds demonstrated.
Time of arrival
Time of arrival , also called time of flight , is the travel time of a radio signal from a single transmitter to a remote single receiver. By the relation between light speed in vacuum and the carrier frequency of a signal the time is a measure for the distance between transmitter and receiver...
(TOA) technique. Typically several GIBs are deployed over a given area of operation; with the total number determined by the size of the test area and the accuracy of the results desired. Different methods of GPS positioning may be used for positioning the array of GIBs, with accuracies of cm to meter level in realtime possible.
The system in patent protected and products are manufactured by the French company ACSA-underwater-GPS (subsidiary of the ALCEN group). Three off-the shelf products are available from the small portable GIB-Lite system to the large torpeado tracking GIB-FT, and including the medium-size,medium-range GIB-Plus system.
History and examples of use
Use of GIBs for underwater tracking and weapon scoring have been in use by the Navy since the early to mid 1990’s. Early GIBswere created for broad ocean area weapons testing by modifying conventional Navy sonobuoys with small OEM-grade GPS receivers
and deploying them from a helicopter or from P-3 Orion aircraft. The GPS data captured by the GIB was modulated over the analog VHF acoustic data stream using frequency-shift keying
Frequency-shift keying
Frequency-shift keying is a frequency modulation scheme in which digital information is transmitted through discrete frequency changes of a carrier wave. The simplest FSK is binary FSK . BFSK uses a pair of discrete frequencies to transmit binary information. With this scheme, the "1" is called...
(FSK). This allows the GPS measurement data to be transmitted and received on legacy VHF sonobuoy receiver equipment. A drifting array of twelve or more GIBs would be deployed in a concentric circular array approximately 7 nm in diameter. Weapon strikes within the array emitted acoustic signatures that were captured by the GIBs and transmitted up to the orbiting aircraft. Post-mission the GPS and acoustic data from the GIBs would be combined to determine an absolute coordinate for the impact location in WGS 84 coordinates.
Example of underwater acoustic-based weapon scoring
GIB type systems have been developed for a variety of specialized applications. An illustrative use of GIBs for underwaterpositioning is the TARGT weapon scoring and training system
The system concept (Figure 1) utilizes an array eight to ten GIBs (Figure 2) moored in a 2 km by 2 km array. In the case of the TARGT GIB, the GPS and RF antennas are located on top of the sensor and the hydrophone
Hydrophone
A hydrophone is a microphone designed to be used underwater for recording or listening to underwater sound. Most hydrophones are based on a piezoelectric transducer that generates electricity when subjected to a pressure change...
, or underwater acoustic transducer
Transducer
A transducer is a device that converts one type of energy to another. Energy types include electrical, mechanical, electromagnetic , chemical, acoustic or thermal energy. While the term transducer commonly implies the use of a sensor/detector, any device which converts energy can be considered a...
, is located on the bottom. The device is approximately 6 ft tall and weighs 35 lbs.
Inert weapon releases from military aircraft strike the surface of the water within the array, emitting an acoustic signature
that is captured by each of the GIBs. Each GIB determines the precise time of the received signal and transmits this time to the deployment ship in near real time. A command and control system located on the deployment and recovery ship combines the GPS data and acoustic timing information to triangulate the impact location and determine the exact impact time in near realtime. Several methods may be used, the most common being a time difference of arrival (TDOA) least-squares solution algorithm. Post-mission data processing is performed to further refine the results, with two-dimensional positioning accuracies of 1 to 2 meters and impact timing accuracies of 1-2 milliseconds demonstrated.