T-POD specification

Data processing:

Fully automatic, using the supplied software, TPOD.exe.

Working depth:

0 to at least 150 m (maximum yet to be determine).

Autonomous operation time:

Up to one year.

Casing:

Polypropylene. Two halves - the upper half contains the transducer and electronics, while the lower half contains the battery pack.

Dimensions:

Length: 0.86 m

Diameter: 0.90 m

Weight:

2.8 kg with no batteries

4.4 kg with 15 alkaline D cells

Buoyancy:

Approximately 1 kg

Mooring lines:

2 x Dyneema®* 740 kg breaking strain lines attached just above the centre of the housing

Hydrophone:

Standard or low frequency.

Standard: 9 kHz to 170 kHz. Centre-opening PODs now have a new transducer design in a larger transducer housing and provide greater sensitivity to lower frequencies. The sensitivity at 130 kHz is fixed by the standardisation process.

Low frequency: gives greater sensitivity (detection range) at frequencies below 50 kHz and is most useful for deep water deployments for beaked whales, or similar species.

Memory:

128 MB of non-volatile memory capable of holding up to 30 million click times and durations.

Batteries:

Standard battery packs hold 15 alkaline D cells and give approximately 90 days running time.

Detection range:**

Harbour porpoise (Phocoena phocoena): in shallow water out to approximately 300 metres from the POD, with a detection function equivalent to 100% detection within approximately a 70 to 100 metre radius.

Dolphins: with louder clicks have a greater range and an unpublished study by Ingram and Englund in Ireland showed detection at approximately 1500 metres from bottlenose dolphins (Tursiops truncatus), moving along the coast of the Shannon Estuary. Other studies are in progress.

Standardisation:

T-POD hydrophones radial variation < ± 2 dB relative to the mean sensitivity.
The standard is detection of 50% of a simulated porpoise click of 1 Pa peak-peak pressure at the T-POD hydrophone transducer. The simulated click has 6 cycles at 130 kHz.

Deep water version:

Pressure-resistant transducer housing and non-buoyant aluminium case.

Detection parameters:

For each 9.3-second slice of each minute, the following operational parameters can be set:

- Target frequency: 16 steps from 9kHz to 170kHz

- Reference frequency: 16 steps from 9kHz to 170kHz

- Bandwidth: 8 steps

- Sensitivity: 16 steps, standardisation is on step 8

- Noise adaptation: Reduces maximum bandwidth logged when the ambient noise level (reference filter output) is high.

- Maximum number of clicks logged in each scan in any minute. This helps to make memory use more predictable.

- Minimum click duration logged can be set for all scans and the number of minutes OFF following each minute ON can be set.

- Click rates up to 5000/second can be generated and logged in an acoustic tank.

- Click timing is to 10 microseconds resolution. Overall click timing accuracy is lower due to clock drift, but is sufficient for logged events to be correlated with timed visual data.

Attitude sensing:

The angle-from-vertical is recorded each minute, enabling the user to ensure that the T-POD has been correctly deployed in a vertical position. The sensor can be set to a pre-selected range to prevent logging until the T-POD is deployed. This allows the T-PODs to be set up and transported some time before deployment, saving power and memory.

Temperature sensing:

 Temperature reading is recorded each minute.