Surveying in Antarctica
For generations mariners have relied on the information contained on Admiralty Charts to safely navigate ships of all sizes around the globe. The technology that the surveyor has at his disposal has changed dramatically. From sextant and lead line to early single beam echo sounders and now to the latest in multi-beam survey systems. HMS ENDURANCE has developed in keeping with these changes and is fitted with a Konsberg EM710 multi-beam echo sounder.
Previous to having multi beam capability any survey platform would be required to run along pre-planned lines while collecting single points of depth along a very narrow single beam directly beneath the ship. At the same time a Side-Scan sonar would be towed behind the platform to “look” between lines of depth data in order to detect any objects which may require further investigation (a practice virtually impossible in ice conditions). Multi beam offers the surveyor a “fan” of hundreds of beams which in the case of ENDURANCE run from 25 degrees below the horizontal plane through the vertical to 25 degrees below the horizontal on the opposite side of the ship. The resulting “swath” is stabilised for heave, pitch and yaw and a very accurate differential GPS position is blended into the solution to position each data point on the sea bed. The system fitted to HMS ENDURANCE produces a swath width of between 3-4 times the water depth, giving the ship the capability to produce lanes of data up to 1200m across that are ideally suited to the narrow inlets and bays of Antarctica. These lanes can provide safe highways for HMS ENDURANCE to operate within when conducting flying or boat operations, as well as providing much needed survey data for the update of published charts.
Figure 1. A multi beam data set draped into the published chart (Admiralty Bay – South Shetland Islands), colour is used to define the depth contours.
The requirement for modern, reliable survey data (very little of which exists) in and around the Antarctic Peninsula is on the increase. The numbers of visitors embarked in cruise ships grows every year. Inevitably with this increase an element of commercial competition will develop with operators wishing to push further south into areas not offered by competitors.
Figure 2. Image shows an example of the reliability of some charting in Antarctica. In this case the charted danger (8 fathom sounding in blue) does not exist so can be removed from the chart allowing safer access to this bay.
HMS ENDURANCE receives her survey tasking from the United Kingdom Hydrographic Office, she also routinely collects and expands her own data sets whilst embarked on tasking in support of British Antarctic Survey. During recent such tasking HMS ENDURANCE surveyed the inside of Deception Island including looking closely at a number of volcanic cones in the area.
Figure 3 Deception Island data set showing the data collected within the confines of the Island. The largest of the cone’s can be seen to the North East of the data set.
Figure 4. Volcanic Cone – labelled Cap 1
The survey team and Ship’s Company of HMS ENDURANCE continue to collect high quality survey data in order to further our understanding of the Antarctic environment and increase the levels of reliable and accurate charting available in the area.
David Sharp.
CPO Surveyor.
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