Lieutenant Commander Richard Mortimer is the Charge Surveyor on HMS Endurance and here is his Dept's description of Work Period 1 - the first of 3 Work Periods that the Ship's Hydrographic Dept. is involved with.
Outline of Work Period 1
Work period 1 was a very busy 4-week period around South Georgia. During this work period we surveyed 4 of the many spectacular bays with the 2 survey motor boats carried, while the Ship completed the remaining sections of the coastal corridor, left from previous deployments. This meant the flight were then used for transiting between the two, for fuel and personnel changeovers, and setting-up shore-side control for the survey.
Shore-side control covers tidal observations and a method of creating a very accurate Global Positioning System (GPS) fix called Differential GPS. Tides are monitored constantly during a survey in order that depth readings (bathymetry) can be reduced to Chart Datume (a standard height) by applying high/low water readings. The observations are conducted using a tide gauge, but in order to check the readings a Survey Recorder (SR) conducts a 25-hour observation.
This entails placing a tide pole along the water's edge - as easy task in the UK with harbours and jetties all around the coast - which often entails rigging a scaffold pyramid, to hold the pole a few metres off the shore. The SR can then observe the changes in height of tide every half an hour, to compare with the predicted tides and the readings on the tide gauge.
One of the surveys we completed was in King Haakon Bay. This survey was particularly special as one of our SMBs (Survey Motor Boats) James Caird (JC) is named after Shackleton's boat James Caird. It was here in King Haakon Bay that Shackleton actually landed his boat, James Caird after the epic journey from Elephant Island. It is a popular bay for the cruise ships, for this reason, an up-to-date survey is crucial for navigational safety.
SMB in Haakon Bay, Courtesy of HMS Endurance
We also carried out significant amounts of photogrametry (a method of mapping/charting from the air) and magnetic observations for the Royal Geological Society. Alongside the survey work is a varied and full programme of support to the Government of the Falkland Islands and South Georgia and support to BAS.
For the second phase of this work period, we worked around Cooper Island on the Southeast tip of South Georgia. While Endurance tackled the open water (over 40m deep work) the James Caird conducted the inshore lines, negotiating rocks and icebergs.
Cooper Island, Courtesy of HMS Endurance
The drive for the survey work around both South Georgia and the Antarctic Peninsula is the rapidly increasing number of cruise ships use the area for eco-tourism. Many of the charts for the areas are still fathometric (made before metrication - so very old). Thanks to the use of GPS (Global Positioning System) the positioning accuracy that can be achieved now means that if we say a rock is in position, then it is within 2 or 3 metres rather than the 30-40 metres of the old charts. So, our aim is to provide safe channels and entries to the bays for the cruise liners before the worst happens.
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Hydrographic Surveying