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Ship's Diary  During her time at sea, HMS Endurance will be sending back regular diaries to keep us all up to date with what is happening on this deployment. Use the links below to read extracts from the diary. Trafalgar Celebrations Multi Beam Trials Summer Highlights Sonar Investigations A Stormy Life Some Interesting Facts Time Zone Changes Eye of the Storm Remembrance Sunday NBCD Its A Knockout Estrela Visit to HMS Endurance Endurance Encounters QE2 Again! St Ippolyts CE Primary School The Engineering Department News from the Flight Department Photos from the Flight Department Communications in Antarctica Kevin Schafer Christmas Message Endurance meets Ellen MacArthur Photos from the Flight Department Coachhouse Publications Update by Nick Lambert, Captain, HMS Endurance Hydrographic Survey Progress Update from Endurance's Hydrographic Surveyors New Year update from the Flight Department BSES Members’ Expedition to South Georgia A Christmas Day Outing Boat Camp South Georgia Update from the Engineering Department BSES Expedition Summary HMS Endurance contributing to World Meteorology BBC Film Crew Feature BBC – Aerial Filming with HMS Endurance Vertical Photography by Lt Scott ‘Stimpy’ Simpson Endurance Enters Port Foster - Deception Island Loadlifting by the Flight Dept February update from the Flight Department HMS Endurance and the 'Ghost Ship' Maxwell Bay Andy Rouse – Wildlife Photographer Site Guidelines Review Team Antarctic Gallery 2005/6 Deployment Gallery by CMEM(M) Pete Morewood HMS ENDURANCE help Norwegians Restore the South Georgia Husvik Villa 2005/6 Deployment Gallery by POAC Andy Johnson 2005/6 Deployment Gallery Part 2 CMEM(M) P Morewood HMS ENDURANCE Lends a Helping Hand Update from Nick Lambert, the Captain of HMS ENDURANCE Engineering Department Update from Lt Matt Liddell, Engineer Officer 2005/6 Deployment Gallery Part 2 by POAC Andy Johnson Warfare Journal by Lt Russ Abbot Penguin Racing Night Deployment Cup April Update from the Flight Department HMS Endurance Hydrographic Survey Progress during Work Period One (South Georgia) As we have mentioned previously this is the first season that we have had the opportunity to use the newly commissioned EM710S Multi Beam Echo Sounder (MBES). This is a particularly impressive and complex piece of equipment, which has revolutionised the ship’s survey output. MBES technology has matured over the past decade and allows increasingly sophisticated images of the seas bed to be captured. To contribute to the safe navigation of other vessels we are primarily interested in the bathymetric, or depth data. This is augmented by an indication of the bottom type. In simple terms the MBES sends out a powerful pulse of sound (the swathe) directly under the ship to 65° either side of the vertical (known as the nadir). The returning acoustic energy, which reflects from the seabed, is electronically divided into a series of overlapping beams. Up to 200 beams each 2° wide are produced across the swathe. The time of each returning beam is precisely measured and the speed of sound through the water applied to determine the depth from that beam’s location. The width of the swathe, in a flat area equates to approximately four times the nadir depth. This is elementary trigonometry. Remember the right angled triangle - the tangent of an angle is equal to the opposite side divided by the adjacent. (For those as old as me - SOHCAHTOA!) We have two back to back right angled triangles, each of 65°. The tangent of 65° is of the order of 2 (try it on a scientific calculator). Thus each opposite is twice the length of the common adjacent and the whole swathe is four times water depth. We also need to know the position of the ship to very tight tolerances. We use a blended inertial navigation position and differential GPS, combining the short term clean nature of the former and the long term precision of the latter to generate a position accurate to less than one metre. This contributes to the accuracy of the positions of the 200 depths across the swathe. The motion of the ship as she rolls, pitches, heaves and yaws is also accurately allowed for. Lastly the refraction of the acoustic energy is modelled to account for variability in sound speed, due largely to changes in temperature with depth. By combining the beams across the swathe and between pings along the ship’s track then very detailed 3D images can be produced. Further the quality of the returning echo can be analysed to determine the reflective properties of the seabed. A flat hard bottom such as rock will reflect well, whereas a soft undulating bottom such as rippled mud absorbs a significant proportion of the sound. Each surface will produce a distinctive response, which may have navigational impact. A muddy sea floor for example is a good holding ground to anchor in. We also use the output of the MBES to keep us safe while surveying. When operating in previously unsurveyed areas the first line we run is particularly important, and will be carefully considered. Running in ‘known’ water, we use the MBES to look with one side into the ‘unknown’. Once the line has been covered we can then safely look further into the unexplored area, by gradually exploring always staying in previously swept areas. A good comparison would be grass mowing or field ploughing. Once the first line is ‘cut’, by running along its edge we can ensure we are safe as we already know what depth to expect, while surveying the next line. During our South Georgia work period we have worked in many different areas, using the MBES extensively. We have operated in unsurveyed waters in the fjords of Cumberland Bay East and West and in the previously poorly surveyed Royal Bay, all on the east coast. To the west we have circumnavigated Annenkov Island, generating a corridor which is typically 800 yards wide in an area described as ‘Inadequate Surveys’. We now have to carefully investigate all the data we have gathered, correct it for height of tide and clean any spurious data from it. The results will be forwarded to the United Kingdom Hydrographic Office (UKHO) who will validate it and then use it to update existing charts, hopefully removing comments such as those near Annenkov Island! The following screenshots may assist in illustrating the points above. This screenshot was captured as we completed a circumnavigation of Annenkov Island, and compares directly with the existing chart below. For scale the survey HMOI 1128 northern element orientated NW/SE is thirteen miles long, we surveyed a swathe of 2 miles wide on this part of the survey. Our corridor around Annenkov Island varies from around 450 metres to 1 nautical mile wide, averaging 800 metres wide. We achieved the circuit of Annenkov during 2 days work, using the nights to work in the adjoining tasked area, where the water is deeper and the ice bergs thus easier to avoid. Here’s the existing chart of a similar area. The orange gridded area is the allocated survey task from UKHO, this northern section being 13x3 nautical miles of which we achieved 13x2. The ‘target’ is the ship’s position at the time of the screen shot. I have sketched on the approximate route we took around the island, initially we worked to the north and west, the second day saw us on the south coast and joining the previous track in the Hauge strait. Note the numerous comments ‘Inadequate Surveys’! We also worked in Royal Bay on the opposite (east) coast of South Georgia. While this bay does have existing data charted, it is an imperial (fathoms for depths) chart, with very few depths specified in its area of 7 miles long, by 4 nautical miles wide. In the existing chart there are approximately 20 depth points in the area we surveyed. Using our lawn mowing method we investigated the vast majority of the bay, over an area of approximately 6 nautical miles long by 2.5nm wide. The indications are that the Ross glacier is retreating as we crossed its present charted position, (although this was probably always in error). We found minimum depths in the vicinity of Pirner point of around 30m; this was within 350m of the shoreline. The existing chart: Here’s the MBES image in the vicinity of Pirner point. Note the concentric nature of our adjacent tracks as we continue on the edge of our previous line in safe water. Also note that the depths are shoaling (ie getting less) to port (ie our left) as we head east (ie to the right hand side of the geographical image). This is shown in the individual depth curve, second graph down on the left, as well as on the waterfall display, third down on left and the water column display, centre bottom. Many people think of this lower image as an ultra sound image. This is indeed what it can be equated to as it takes a slice across the swathe from immediately below the MBES. The dark blue indicates clean, quiet water, the light blue may indicate disturbances in the water, such as bubbles, fish, interference from other sonars or flow noise over the system array. The black line through the red indicates the detected bottom. In common with the quasi 3D waterfall display this is definitely sloping to port (the left). The main geographical display captures the data and gives it a colour value to reflect its depth, blue for deep, red (danger) for shoal or shallow depths. As you can imagine we watch this window particularly closely. In deep water our swathe width is proportionately wide, as we explore shallower water so the swathe width reduces, which we have to be very aware of as we get less room to manoeuvre in! The final series of images are from Cumberland Bay East, where we closed to within 400m of the snout of the Nordenskjold glacier in an area previously unsurveyed, this was very satisfying, and will hopefully contribute to the navigational safety of other vessels approaching so close. A word of caution though, this glacier too is retreating and so it is likely that the snout will continue ‘calving’ (shedding) significant volumes of ice, which could endanger vessels, so don’t go too close! In this MBES image it is of note how flat the floor of the glaciated valley is. Just imagine the awesome power of the bulldozing effect of the advancing glacier. Further north in the bay we have seen evidence of terminal moraines, perpendicular to the axis of the fjord, where the glacial material has been dumped at a previous snout position. Also the steep sides of the classic ‘U’ shaped valley are very marked at the extreme edges of the glaciated areas.
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