|
Working depth: |
0 to 100 m and probably more. A single C-POD has been
tested to destruction and failed at 220 m. |
|
Autonomous operation time: |
Up to a theoretical maximum of 5 months for the standard version using
10 alkaline
D-cells. Sea trials in the deployment area are required in order to
determine more realistic limits. |
|
Housing: |
Polypropylene. Contains the transducers, electronics
and battery pack. |
|
Dimensions: |
Length: Early versions: 8 D-cells, 535 mm. Current
version: 10 D-cells,
655 mm. Diameter: 90 mm |
|
Weight: |
8 alkaline D-cell version: 1.7 kg without batteries, 2.9 kg with batteries.
10 alkaline D-cell version: 2.5 kg without
batteries, 3.9 kg with batteries.
|
|
Buoyancy: |
8 D-cell version: approximately 0.5 kg
10 D-cell version: approximately 0.7 kg |
|
Mooring: |
A stainless steel mooring ring with 18 mm polypropylene line attached just above the centre
of the housing to minimise tilt in a current. A security line can be
attached to the lid. |
|
Hydrophone: |
20 kHz to 160 kHz, omni-directional hydrophone in
a large-diameter housing to reduce surface noise. The transducer
design avoids strong resonances and the transducer element mounting design
gives high resistance to impact damage. |
|
Memory: |
Removable
high density Secure Digital (SD) memory card. Two SD cards supplied. |
|
Batteries: |
Battery packs hold 10 alkaline D-cells (the early
version held eight). The
battery housing is sprung to reduce battery damage from end impacts. |
|
Detection range: |
Maximum detection range for porpoises is approximately
300 metres. Dolphins are detected at much longer distances.
|
|
Standardisation: |
The complete instrument is rotated in a sound field
and adjusted to give a radially averaged, temperature corrected,
pressure reading within 5% of the standard at 130KHz (±0.5dB). The standard
is currently being measured by the National Physical Laboratory.
Radial variation < ±2 dB relative to the mean sensitivity. |
|
Deep water version: |
To 4km. Pressure-resistant transducer housing and non-buoyant aluminium case. |
|
Detection method: |
Digital time domain waveform analysis, using duration
(5μs resolution),
intensity, bandwidth, frequency and envelope criteria to select possible
cetacean clicks in the range 20-160 kHz. |
|
Detection parameters: |
Centre frequency, frequency trend, duration, intensity
(8 bit), bandwidth, envelope slope are logged for each click. |
|
Ambient noise: |
The C-POD intensity measurement is standardised to
allow continuous assessment, when cetaceans are detected, of the minimum
intensity of clicks that are detectable at that time. This new method
will allow assessment of the actual effect of ambient noise on click
detectability, which is difficult or impossible to obtain from standard
measures of noise as they lack crucial information on short-term
temporal variations. |
|
Attitude sensing: |
The angle-from-vertical is recorded each minute,
enabling the user to ensure that the C-POD has been correctly deployed in a
vertical position. The sensor can be set to a pre-selected range to prevent
logging until the C-POD is deployed. This allows the C-PODs to be set up and
transported some time before deployment, saving power and memory. |
|
Temperature sensing: |
Temperature is recorded each
minute. |