Thursday 7th October - Rob Eavis, Dave Harley

During August and September we squeezed (!) quite a lot of Crusader trips in, to get as much prepared for Hidden Earth and a Descent magazine article as possible. Once these were each completed I think we all welcomed a short breather for a few weeks. This allowed us to step back and review the project as a whole. 

After some short review time, it seems the main outcome of such a discovery is of course the survey, and the fact Crusader is right at the far end of Oxlow and that Oxlow connects to Giants means it’s quite a big survey. Much of the 3D file is from old data from the 70’s, which the paper survey is created off. The data has then been somewhat translated to make it suit the survex format. Quite a bit of Oxlow has been redone with a DistoX, with only half of Pilgrims Way and the Chamber of Horrors connection running off old data, whereas none of Giants has been redone.

Now I’m not sure whether people think the old ways or the new produce a more accurate survey, however what we are very aware of is that when the two caves are connected together digitally there is a 12% loop closure error. Over such a distance that correlates to a 77m horizontal and 10m vertical error! Obviously not an acceptable figure. 

One potential explanation would be that the entrances are incorrectly located, a theory soon to be tested using a high accuracy differential GPS device. The more obvious explanation is that the surveys contain multiple errors, a more challenging theory to disprove. And of course we don’t know if it’s the old or new. So with that in mind we’ve started the Giants Resurvey Project (aka HavingARestFromStupidlyLongTripsInCrusader Project).

The first trip was myself and Dave Harley, starting from a permanent station at the Giants entrance (to later be connected in to the GPS) and heading in. It was Eldon pub night so we only allowed ourselves a short trip, meaning we only got as far as the start of the traverses above the Crabwalk (heading towards the Windpipe). That said it was a lovely trip, clean and easy, a refreshing change! The results are already revealing, with a 20m horizontal and 7m vertical difference with the old data!

I reckon on the next trip we’ll get to the start of the Chamber of Horrors connection. Hopefully we’ll tie it all in lovely at that point, enabling us to not have to repeat the connection survey! Plan then will be to head on down to East Canal to complete the backbone of the Giant. Then we can start adding his limbs….

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