<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> </head> <body><div class="auto-created-dir-div" dir="auto" style="unicode-bidi: embed;"><style>p{margin:0}</style><blockquote style="margin: 0 auto; padding: 0 2em; border-left:2px solid #00ADE5; white-space: pre-wrap "><div class="auto-created-dir-div" dir="auto" style="unicode-bidi: embed;"><blockquote style="margin: 0 auto;padding: 0 2.0em;border-left: 2.0px solid rgb(0,173,229);"><br><div class="auto-created-dir-div" dir="auto" style="unicode-bidi: embed;"><p>Dear All,</p><p>In 2018 I realised that some re-survey work was needed in Wet Sink (Slaughter Stream Cave), hereafter termed 'SSC' in support of of a Gloucester Speleological Society water tracing study. Also I have started a speleogenesis and geological study into this cave, which at 13km long and ~ 110m deep and largely formed in dolomite is a curious and impressive beast! It's 3 times longer than the next longest FOD Cave, Miss Graces Lane, and although entirely natural it contains interesting iron and manganese (?) deposits, fossil layers and archeological remains such as 'Norman' the dog skeleton. The cave has even featured in an episode of 'Extreme Archeology'.</p><p><br></p><p>The cave was well surveyed mostly around 1991 to 1993 with a lot of hard work put in by GSS and RFDCC, using best techniques available at that time (Suunto compass/clino and tape) under the leadership of Paul Taylor. <span style="display: inline;">This resulted in a comprehensive Compass software database and a 1995 2D plan view drawn in ink at 1:500 scale on transparent paper and photo-reduced scale versions of same. </span><span style="display: inline;">A further ~1.9 km was later discovered and surveyed during the period 1997 to 2000 in the 'Remelt Plant' and 'Heat Exchanger' series and this was added to the Compass database and shown as a line drawing on issued maps, but the passages still not yet drawn up. A redrawing of the cave plan was also made by Paul around 2017 in A3 pdf digital format as part of a FOD wide survey dataset compilation including over 110km of caves, mines and tunnels and lodged with the UK survey database. </span><span style="display: inline;">The survey drawings were all great for finding the way around and relating passages to the numerous sinks and other shorter caves in the same catchment area, such as Seymours Swallet and Redhouse Lane Swallet. However elevation plots were not made and not many passage cross-sections recorded. Also the inclination data gave unrealistically deep values (>20m too deep) for the deepest point in the cave relative to the Slaughter resurgence at the River Wye near Symonds Yat. Also some sections of streamway did not have realistic slopes resulting, in a few extreme cases even sloping partly the wrong way. The cave plan was drawn up by Paul using the Compass survey line plots, coordinates and cave survey sketches. Around 60% of survey stations had LR recordings, but only about 20% had UDs and therefore elevation views and relationship between sinks, springs in the cave and sumps and geological layers could not be precisely established. </span></p><p><br></p><p><span style="color: rgb(255,0,0);font-weight: bold;">Advice request: 1) </span>Compass has an easy to use magnetic declination database built in, where you feed in the date, lat/long and elevation and it gives you magnetic declination for anywhere in the world. I have used this and incorporated the values into the data acquisition spanning 1991 to 2020. Does anyone know of an alternative source of historical magnetic declination data for UK against which i can check this ? Its especially important in SSC because many cumulative passage lengths exceed 2km and any systematic error of say >0.3 degrees will move cave points ~10m horizontally. Declination from true north was apparently -5.4 deg in 1991 and is -0.74 today.</p><p><span style="color: rgb(255,0,0);font-weight: bold;">Advice request 2) </span>Should I apply declination corrections to match True North or to match NGR? End plan is to draw up new entire survey in Therion. NGR Convergence is about -0.48 degrees from True North here. </p><p><br></p><p>The summary work flow so far has been:</p><p>a) Check/clean up Compass database using original survey notes and drawings, adding in whatever LRUD data is available. Paul Taylor is still involved with this project and has done a sterling job finding original survey sketches, data and cave drawings after 27 years for me to use and he has worked on several of the re-survey trips. Paul is leading the present water tracing study too. </p><p>b) Untie all loop closures so that original and new data acquisition can be compared like for like.</p><p>c) Compare new pocket topo data (~4km recorded so far) along key routes in the cave, in particular the streamways, to the old data and focus further attention where its needed most. This has been achieved both by adding pocket topo data into Compass for a while on home PC. But then later getting all the Compass data successfully into pocket topo using Footlegs converter. This means that in the cave I can now see old vs new data in 'real time' in pocket topo and look out for particular survey needs and see roughly what is coming next along the survey route. Also I have been able to add any little bits which were missing before (this has added cumulative ~300m to the surveyed cave length so far). The new data recorded has elevation plots and plenty of passage x-sections to help with speleogenesis and water tracing work. DistoX2 calibration has been checked before starting work on every trip and recalibration needed twice so far. The comparison in plan view so far between old and new surveys is pretty good, albeit with some progressive offsets up to around 20m in spatial position, but all passage segments match well, showing no significant errors before, such as missed stations or reversed azimuths. The one major loop in the cave down 'Coal Seam Passage' that rejoins the streamway had a 1993 mistie ~ 12m horizontally, again pretty good, but now achieved in pocket topo to <2m horizontally and 0.2m vertically.</p><p>d) Side branches that 'stand-alone' and seem fine in the old data such as Pirate Passage (1063m) and Echo Passage (770m) and which have fairly complete LRUD data have been tied into the new pocket topo dataset and will not require further attention until drawing up is done digitally in Therion.</p><p><br></p><p>Biggest differences old/vs new datasets seen so far are where steep or complex passages occur, such as the Entrance Series which has a double spiral going down to -55m below entrance and then gradual depth 'drift' going up or down streamways due to old inclinometry being slightly off, but which over long distances does accumulate significantly.</p><p><br></p><p><span style="color: rgb(255,0,0);font-weight: bold;">Advice request 3): </span>If we find original suunto clinometer used and see any calibration error, is there any reason not to apply a correction retrospectively to the old data? This would improve accuracy of the old data retained in the new database and reduce the new acquisition required. Has anyone had suunto clinometer issues before that they overcame?</p><p><br></p><p>Foward plan on surveying is to complete whatever new acquisition is needed in pocket topo, probably a further ~2.5 km. Then after all survey data is cleaned up, start work in Therion and in the end produce and publish a digital survey drawing fit for such a fine and interesting cave. BTW I have almost zero previous knowledge of Therion at present. This can then form a reliable 3D framework in which to fit the water tracing and speleogenesis observations.</p><p><br></p><p>Some rock sampling (~50 samples) have already been collected and are already at Univ Manchester geology department for future petrographic analysis to quantify/understand dolomite vs limestone, but covid has held this up for at least 1 year already.</p><p><br></p><p>There is probably a fascinating story to unravel on Iron and Manganese mineralisation in SSC which we will only start to work on in the coming months. BTW furthest parts of the cave take ~ 5 hours fairly strenuous one way travel time to reach, so some underground bivi's will be used and 10 to 15 hour trips can be split between 2 or 3 days.</p><p><br></p><p><span style="color: rgb(255,0,0);font-weight: bold;">Advice Request 4):</span> Can anyone suggest improvement to the work flow in progress or suggest other things we didn't think of? Is there anything special about Therion I need to know at this stage that would affect present work flow?</p><p><br></p><p>After ~11 survey trips so far I am finding it difficult to find enough survey helpers from GSS/RFDCC on a regular basis to complete reaminder of the acquisition within a reasonable time. Is anyone on this list keen to help in say November/December 2020? All help will be properly acknowledged and i want the end survey result to be issued under GSS club name but 'open access' after completion. </p><p><br></p><p>Please see attached plan summary jpeg. </p><p><br></p>Regards, <br><div>Mark Tringham</div></div> </blockquote><br><br><div>Mark</div></div></blockquote><br><br><div id="" class="">Mark</div></div></body></html>