POSIDONIA is a system dedicated to the positioning of manned, teleoperated or autonomous underwater vehicles down to 6,000 m depths.
Fields and conditions for use
- Fields of operation
- long profile follow-up
- rough seabed
- noisy environment (support ship)
- survey mode (vehicle beacon on responder or transponder mode)
- sea state £ 5
- sound velocity profile measured and known (using XBT 700 Sippican probes and Levitus data)
- vehicle operating in a maximum conical angle of ±45° under the support ship
- maximum water depth= 6 000 m
DGPS is highly recommended for vessel surface positioning. When it is performed without DGPS, the greatest error on positioning comes from the GPS.
At ± 1s, 0,5% of the slant range is the navigation dispersion value given by the manufacturer (68 % of calculated points are inside a 1s-radius circle).
At ± 2s, the operational navigation dispersion is 1% of the slant range (95% of calculated points are inside a 2s-radius circle).
- Conical working area under the support ship
- nominal: ± 30° (above, dispersion increases)
- maximal: ± 45°
- Signal to noise ratio (acoustic signal power received/noise power from the ship received by the array):
- 30 < S/B < 40 dB for a normal dispersion
- 20 < S/B < 30 dB for a degraded dispersion (coefficient from 2 to 4)
- loss of points when S/B £ 20 dB
POSIDONIA is made up with 2 sub-systems:
- Beacon sub-system
- 4x1 RTT vehicle/mobile beacons
- 4x1 RTT fixed point beacons
- 4x1 ET/RT mini USBL beacons
- Ultra short baseline sub-system
- flush or deployable acoustic array
- electronic cabinet
- operator workstation (including IHM)
- acoustic array and electronic cabinet's connecting cable
Based on measures performed by USBL combined with chirp signals (linear frequency modulation), POSIDONIA makes possible the positioning of underwater vehicles to a maximum depth of 6,000 m.
- From 8kHz to 14kHz for interrogations with monochromatic signals
- From 14,5kHz to 17,5kHz for reception with modulated signals
- Define calibration trajectories:
- after the array deposit
- if the navigation dispersion seems to degrade
- if one shipborne equipment is replaced (attitude control system, DGPS).
- Use a HDMS attitude control system
- THALES, Ixsea Oceano