Chelonia Limited

  Cetacean Monitoring Systems

 

C-POD specification

C-PODs log very large numbers of clicks that have some resemblance to cetacean clicks. Cetacean detection is performed in post-processing by the detection and classification of coherent sequences 'trains' of clicks found within the raw data.

Software:

CPOD.exe carries out objective automated data analysis to find click trains in the data and identify those produced by dolphins, porpoises and all echo-locating cetaceans except sperm whales. It also provides fast display and export of data and enables users to change C-POD settings. Provided free, with free upgrades. The software and C-POD Software Guide can be downloaded here.

Working depth:

C-POD: At least 100 m. A single C-POD has been tested to destruction and failed at 220 m.
DeepC-POD: At least 2 km.

Autonomous operation time:

Maximum running times seen are 200-212 days and depend on battery quality. With good quality, high capacity D-cells, more than 4 months can be expected.

Housing:

C-POD: Polypropylene.
DeepC-POD: Aluminium.

Dimensions:

C-POD: Length: 670 mm. Diameter: 90 mm
DeepC-POD: Length: 680 mm. Diameter: 100 mm

Weight:

C-POD: 2.1 kg without batteries, 3.5 kg with batteries.
DeepC-POD: 7.15 without batteries, 8.6 kg with batteries.

Buoyancy:

C-POD: Approximately 0.7 kg. This makes C-PODs self-orientating and increases the chance of recovery if the mooring fails. A web link engraved on the outside has enabled many PODs to be returned to their owners by people who have found them on sea shores, sometimes more than 2,500 km from home.
DeepC-POD: -3.1 kg, not buoyant.

Mooring:

C-POD: 3 x 10 mm holes in the lid.
DeepC-POD: 1 x 12 mm hole in the lid.

Hydrophone:

20 kHz to 160 kHz, omni-directional hydrophone in a large-diameter housing to reduce surface noise. The transducer mounting and housing design gives high resistance to impact damage.

Memory:

Removable 4GB SD card. Two SD cards are supplied with each C-POD.

Batteries:

Battery packs hold 10 alkaline D-cells. The battery housing is sprung to reduce battery damage from end impacts.

Detection range:

Maximum detection range for porpoises is approximately 400 metres. Dolphins may be detected at >1 km.

Standardisation:

See C-POD standardisation and calibration.

Click selection:

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.

Cetacean detection:

Coherent click trains are extracted and classified by the KERNO classifier. This classifier is a fixed component of the process to give long term uniformity of performance. Secondary encounter classifiers are available to enhance performance in specific locations e.g. the Hel1 classifier gives less than 1 false porpoise positive minute per 250 million clicks logged in low density areas of the Baltic Sea.

Species classification:

Porpoises and other narrow-band high frequency (NBHF) species can be distinguished from broadband species. Some discrimination of groups of species within the broadband species may become possible when sufficient data is available. Every species tested has given good detection performance see Species detection.

Settings:

The default settings cover all species and most environments. In locations with high levels of ambient noise, which are usually due to substrate transport by currents, standard low sensitivity settings may be required.

Attitude sensing:

The angle-from-vertical is recorded each minute, enabling the user to check after deployment that the C-POD was deployed in a vertical position, and giving information on currents. A range of angles at which the POD will log can be set. This allows the C-PODs to be set up well in advance and transported in a horizontal attitude saving power and memory.

Temperature sensing:

Temperature is recorded each minute.

Maintenance:

The external surfaces of the C-POD are simple and tough allowing robust methods of removing bio-fouling. The lids use a dual O-ring design with grease-free lubricants and these have proved highly reliable.