Trackdyne Documentation
Main ❯ Navigation & tracking systems ❯ VigilArc USBL: Data brief
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VigilArc USBL Data brief |
General information
VigilArc USBL is an underwater acoustic ultra-short baseline (USBL) navigation system designed to determine the location of underwater objects marked with acoustic responder-beacons VigilArc Tag using a direction-finding transceiver antenna VigilArc Array.
System composition
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VigilArc Array Direction-finding base station with an RS-422 interface cable |
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VigilArc Tag Responder-beacons (one base station can work sequentially with a maximum of 16 responders) |
| VigilArc Deck Autonomous power supply and switching unit for the base station |
Tasks to be solved
- Determining the location of up to 16 underwater objects in the water area (tracking underwater objects)
- Determining the relative location (azimuth, distance, depth)
- Determining the absolute location (latitude, longitude, azimuth, distance, depth) when connected to an external GNSS and compass (or GNSS with compass function)
Distinctive features
- Compactness, long range and maximum ease of use make it possible to use the VigilArc system to work with various ROVs and AUVs, as well as with divers, in any combination
- The highly versatile beacons can be used either in a standalone version with a separate battery pack or integrated with the carrier for both power and data
- Measurements from the system can be combined with external GNSS position and compass data on a host computer to calculate the geographic coordinates of underwater objects.
- The VigilArc Array antenna is mounted on a pole over the side of a vessel and connected to a 12 V / 3.5 A power source and a host PC. The antenna provides measurements of beacon azimuth and distance relative to the antenna.
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| Installation diagram of the VigilArc Array antenna The antenna is mounted on a rigid pole so that it is no closer than 2 meters to the surface of the water and no closer than 1.5 meters to the lowest point of the vessel. The antenna offsets relative to the position reference point and the angular offset between the antenna zero and the GNSS compass are set |
Interfacing schemes
Working in relative coordinates
For relative location measurements, the antenna is interfaced with a host PC using the VigilArc communication protocol. The antenna is connected to the PC via VigilArc Deck, which converts the interface to USB and powers the antenna.
In this case, the data and functions available to the user are:
- Azimuth (horizontal angle) to the responder-beacons in use;
- Distance to the responder-beacons
- Depths of the responder-beacons
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| Wiring diagram for working in relative coordinates |
Working in absolute coordinates
To calculate the absolute location of the responder-beacons, the host PC must combine the antenna measurements with geographic position and heading data. The antenna is connected to the PC via VigilArc Deck, which converts the interface to USB and powers the antenna. Additionally, an external GNSS system with compass function, operating via the NMEA 0183 protocol (RMC and HDT sentences), is connected.
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| Wiring diagram for working in absolute coordinates |
Combining these measurements provides the data needed to calculate:
- Absolute geographic coordinates of the beacons and depth
- Azimuth (relative to north)
- Distance
Geometric limitations
Since the location of the VigilArc Tag responder-beacons is determined from the horizontal angle of arrival of the signal, the slant range and the depth difference, the antenna array of the VigilArc Array direction-finding station has the highest sensitivity in the angle range from 0° to 85° from the horizontal. The system accuracy may decrease when the responder-beacon is close to the nadir direction.
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| Geometric limitations of VigilArc Array 1 - Direction-finding antenna, 2 - upper hemisphere, 3 - working zone (0° .. 85°, 0 .. -85°), 4 - accuracy reduction zone (85° .. -85°) |