C-PODs log very large numbers of clicks that have some resemblance to
cetacean clicks. Cetacean detection is performed in post-processing in
the CPOD app by
the detection and classification of coherent sequences – trains – of
clicks found within the raw data.
Software app: |
The CPOD app (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 app and C-POD
Software Guide can be downloaded here. |
Working depth: |
At least 100 metres. A single POD has
been tested to destruction and failed at 220 metres. |
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: |
Polypropylene. |
Dimensions: |
Length: 670 mm. Diameter: 90 mm. |
Weight: |
2.1 kg without batteries, 3.5 kg with batteries. |
Buoyancy: |
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. |
Mooring: |
3 x 10 mm holes 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 8GB 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 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. |
Angle 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. |