Freesteel Blog » A little bit of Austrian caving

A little bit of Austrian caving

Saturday, August 16th, 2014 at 7:25 am Written by:

It rains and rains and just won’t stop. It’s also gotten pretty cold and I’m having to wear all my clothes that aren’t damp from lying in the tent. The last day of warm sunshine was six days ago where I stood on takeoff for 2 hours as paragliders wafted past and went down in the totally dead air of that day.
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See the smile? I want more flying. Some canyoning would be good too, but it ain’t going to happen on this trip.

When I finally took off I flew in a direct straight line across the valley beyond the highway and golf course, and then had to walk 5 miles back via an ice cream stand to Base Camp for a lift back up the hill, after which I drove down, fetched my glider, and drove back up again for the walk up to Top Camp (the Stone Bridge).
glideland
Here’s the outside view of Top Camp:
topcampsite
And this is the inside:
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It’s both a rock and a hard place with nothing in between, but it is still better than tents because it is larger, cavernous, and not like a box of damp fabric that progressively rots things as each day passes.

I dropped into the far end of Tunnockshacht down to the new connection to Arctic Angle. Becka was away with the Austrians on a different expedition and couldn’t warn me that it was going to be an unutterably deep one. That wasn’t the problem. The problem was getting terrifyingly stuck in a U-bend crawl while weaseling around the C-leads waiting for the guy with the drill to rig a rope traverse along a ledge of an undescended shaft to access the phreatic continuation. Then we surveyed about 100m until it crapped out, and hauled ourselves back out by 2am.

I forgot to take any pics, so here’s a photo of a nosy horse’s nose:
horsenose
On Tuesday I went to the newly discovered Balconyhohle. (The horizontal entrance is from a ledge within the side of a hole.) I was cold and had to keep eating. We killed a couple of going leads there too, but there’s enough unexplored ways on to keep this one spreading further underground. This has been the big find of the expedition. It’s a lot of work to keep up with the mapping.

Here’s a picture from the walk back to the carpark from Top Camp in the morning:
braungap

Since then I’ve been working on the Adaptive Clearing stay-down linking killing the bugs one at a time while all my HSMWorks buddies have been at a big planning meeting in Copenhagen this week. It seems like an endless grind. Anyway, I don’t plan to go there again, and the ferry between the UK and Denmark is being terminated this September.

One of the things that crashes the system is when the A-star linking can’t find a way to connect from point A to point B, and spreads out through every single cell in the dense weave until it runs out of memory.

One obvious solution is to generate a weave that has a wider cell spacing and solve the routing issue in it, but this is too complicated. I worked out another way, which is to deny it access to most of the interior cells of the fine weave that are nowhere near the boundary or on the theoretical direct line route. The A-star algorithm is so powerful that it will find a way round, even though the domain would look so much more complicated. This initial result becomes the starting solution for the linking path, on which the PullChainTight() function is called. This is actually a bad name for it. It should be called RepeatedlySpliceStraighterSectionsIn(), but this discription wouldn’t remotely be so compelling to the imagination.

This will get implemented only if absolutely necessary. The thing about the linking routine is that it does not need to work 100% of the time, because it can always fall back to the old way of retract linking, which is what everybody puts up with right now, so it might not be worth expending too much effort for the last 2% of awkward cases where the reliability is going to be questionable anyway. In software development the trick is to know when to stop.

Time to work on some cave surveying software today. Maybe I’ll get a flight in tomorrow. Hope so.

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