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Ice Surveillance
Ever wondered how you know where all the icebergs are? Its primarily
accomplished by specially equipped aircraft that perform wide area surveys that
locate all the icebergs. Several government agencies and private companies do
this work and most report the iceberg sightings to the Canadian Ice Centre and
the International Ice Patrol who then pass this information on to shipping in
the Atlantic.
 Provincial Airlines B-200 Special Missions Aircraft.
 Canadian Ice Center's Dash 7
 International Ice Patrol's C-130 Hercules
While the types of aircraft used varies
widely they nevertheless have many things in common, chief amongst these is that
all dedicated reconnaissance aircraft have powerful radar systems capable of
locating icebergs while they are still a long way from the aircraft. While this
sounds straight forward the physics of glacial ice makes reliably detecting it
difficult.
Radar detection of icebergs is limited by several factors,
including radar cross-section (RCS) and reflectivity; Glacial ice found on the
Grand Banks has a reflection coefficient of 0.33, which means that it reflects
radar waves 60 times less than a ship of equivalent cross-sectional area, Ice is
not frequency sensitive, and the response of ice to various radar bands is
virtually the same. The maximum range of radar contact is proportional to the
fourth root of the cross section area of the berg. The radar cross-section (RCS)
has very little to do with the physical size of the iceberg, and more to do with
the amount of radar energy it can reflect. The table below shows the result of a
1986 study of iceberg detection by radar.
Size |
Height (m) |
Length (m) |
Ave. RCS (sq.m) |
| Large |
46 - 100 |
120 - 220 |
180 |
| Medium |
15 - 46 |
60 - 120 |
132 |
| Small |
5 - 15 |
15 - 60 |
17 |
| Bergy Bit |
1.5 - 5 |
5 - 15 |
5 |
| Growler |
1.5 |
5 |
0 |
What this table shows is while a medium size ship may have a
radar cross section of around 150 m a similar size piece of glacial ice will
only have a radar cross section of around 10 m making it only detectable at
around 25 miles as opposed to the same size ship which could be detected at 125
miles. In addition to the variable RCS the physical shape of the iceberg can
compound the detection problem. Take for example a wedge shaped iceberg, if the
radar is "looking" at the back slope the radar energy will be scattered and
almost no radar energy will be reflected back to the receiver. Sea state also
affects iceberg detection, if the waves are high, small icebergs can easily be
obscured down in the wave trough. Each type of radar uses different principals
and operating methods to compensate for these detection problems. Additionally,
there are ways of planning an iceberg survey to compensate for the detection
difficulties. In general terms most ice reconnaissance utilizes a grid pattern
search that provides a high probability of detection through overlapping radar
coverage and the ability to "look" at targets from many different angles. |
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Through careful mission planning that
allows for 75% overlapping radar coverage and also allows the sensor to view the
icebergs from many different angles, Provincial has managed to raise its
probability of detection to 85% which means that we are able to report
conclusively the position of all icebergs within the survey area.
Several different types of aircraft and sensor
packages are used for iceberg reconnaissance. Both the International Ice Patrol
and Canadian Ice Services use large aircraft equipped with Side Looking Airborne
Radar (SLAR), IIP uses an additional Forward Looking Airborne Radar (FLAR) to
try and reduce the confusion between radar returns from ships and icebergs.
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Provincial Airlines performs iceberg reconnaissance for both the offshore
oil and gas industry and the Canadian Ice Centre using its B-200 special
missions aircraft. While originally designed to be an executive transport
aircraft, Provincial's aerospace division refitted the aircraft to conduct
Maritime Surveillance missions by modifying the airframe and installing a
complete electronic sensor package that includes a 360 degree Anti-submarine
warfare ( ASW) radar, a thermal imaging system, high powered gyro-stabilized TV
camera system, and a computerized data collection and management system. While
the B-200 is a fairly small aircraft it nevertheless is capable of carrying the
complete sensor package and crew on ice reconnaissance missions of over 1,000
miles. |
This sensor package combined with over 20 years
of ice reconnaissance experience has proved to be the perfect source of cost
effective ice information. Why then do we need 3 different agencies performing
iceberg reconnaissance? Apart from the fact that icebergs are present over a
huge geographic area spanning hundreds of thousands of square miles of one of
the harshest environments in the world, each one performs a different
function.
International Ice Patrol
IIP's mandate is to
establish the Limit of all Known Ice. To complete this mandate, IIP usually
concentrates their activities in areas well to the south and east of the Grand
Banks, in a normal ice season the extreme southern limit is located at around 40
degrees North Latitude. International Ice Patrol is operated by the US Coast
Guard from Gotten Connecticut, but fly out of St. John's Newfoundland every two
weeks between March and June each year or until the southern limit of all known
icebergs recedes above 48 degrees North.
Canadian Ice Services
CIS's primary air reconnaissance effort is concentrated in the
Gulf of St. Lawrence in the Spring of the year and the Canadian Artic in the
Summer. Their mission mandate is a combination of tactical support for shipping
operations and establishing Canada's jurisdiction over the
Artic.
Provincial Airlines
PAL's primary ice reconnaissance effort
is conducted over the Grand Banks and Offshore Labrador, with the occasional
Davis Strait/Baffin Bay surveys. Provincials iceberg reconnaissance differ from
both IIP and CIS in that we specialize in radar detection along with visual
conformation. All data collected is automatically correlated into a real-time
electronic map of regional ice conditions. While all this effort may seem a
little extreme just to find a few icebergs it is nevertheless necessary to
ensure that the multi-Billion dollar marine industry can function safely in the
ice infested waters of the North Atlantic.
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