Saturday, October 15th, 2016 at 2:20 pm - - Cave, Hang-glide, Kayak Dive

Maybe I’ve got writer’s block. I’ve not even filled these into my logbook. I call it a hat-trick if I do a cave trip, a hang-glider flight and a dive in the same week. This is the fourth time I’ve done it. Generally speaking, the individual events are not all the greatest: the dive was pretty murky, the cave was gritty, and the flight was ridgy. Can’t complain.

The wreck of the Azmund is in Holyhead harbour about a mile of paddling out from the beach.

It was dark and murky and we didn’t find the way back to the boilers after starting on it. The wreck is huge though. Part of the metal juts out of water at low tide.

On the way back we discovered why the beach we launched from is not popular with kayakers — it dries out to about 500m. We couldn’t see our boats after the first time we walked back with a load to the car.

That was Saturday. There was a pleasant day out at Moelfre, with some people being terrified of the currents, but it was the wash from the joy-riding lifeboats that nearly sunk us. The image of the almost breaking 4 metre high wall of water that came upon us while we were anchored in the shallows of Rat Island a few minutes after they zoomed through the channel is going to live long in my memory. The second dive worked out well when we found the remains of the Royal Charter in the sand after groveling in the shallows among the kelp where it was supposed to be until giving up.

Then there was a cave trip to the far end of Ingleborough Show Cave (the only photo of which I have is a line of cavers getting changed on the footpath), followed by a quick escape home ostensibly to start clearing out the house, but which was in fact an excuse to be in North Wales for a flight off Penmaenbach.

I landed on the dwindling beach at high tide after an hour of very smooth sailing in the sea air.


A concrete breaker was hired to smash up and take down the floor. We filled a skip with the crap a day later with some help from friends.

Now we live in a building site. Again. And it’s mid-way through October.

Monday, August 15th, 2016 at 9:20 pm - - Cave

This one has been on our minds since we were caving novices in CUCC (back in 1987) when some of the big boys went to dive the sumps in Rowten Pot and had a bit of an epic. Twenty-nine years later Becka and I used the rigging put in for the Eurospeleo conference, took a small pony cylinder and checked it out.

It was lovely with masks, warm hood, bright LED lights, proper wetsuits (much better than what they had in the bad old days). We went back and forth a couple of times without the tank, and then exited through Valley Entrance — with some complaining at the short pitch from the streamway, which I climbed out and she whinged at, in spite of the fact that she goes bouldering most weeks, and I don’t because I hate it.

Thursday, July 14th, 2016 at 7:57 am - - Cave

To distract myself on the underground camp of terror I stripped down my hang-glider logging device and took it down with a string of temperature sensors, barometer, humidity sensor and light cell and stuck it in a box in the corner with the string dallas temperature sensors extending out along the clothes line some ways from the tent.


The tent was a home made affair designed to be light and sleep four people. The fabric was slightly water resistant. There was immediately a condensation problem with cavers waking up in the morning with the sleeping bags soaking.

As a consequence people began leaving the front door to the tent wide open which meant that it was not a lot warmer inside than out.


Key: The red vertical lines are in increments of 5 hours, horizontal lines are increments of 1 deg C (when applicable). Cyan lines are the temperature measuring devices, some inside and some outside. Cave temperature was around 2.9degrees, while inside the tent it got to 5degrees in the early part of the night.

The four lumps of yellow on the lower line are from the light sensor and represent: (1) first arrival at camp and setting up the logger, (2) return to the camp after an afternoon of caving, (3) waking up in the morning, (4) returning back to the camp for packing up and leaving.

There is a sudden spike up in temperature when I dropped some of my spare clothes onto a sensor that I took off ready for the long climb out.

The upper red trace is the humidity x 0.1 and varies between 95% and 88%. The middle white trace is the temperature logged by the humidity sensor itself. The lower white line below the zero is the barometric reading, which spends its time around 88000millibars corresponding to about 1200m altitude.

Finally the yellow line is the dewpoint temperature, which varies between 2degrees and 4degrees.

Some condensation was briefly encountered when we first got into the tent slightly sweaty (and the yellow and white lines crossed over). For the first half of the night the dewpoint temperature differential was at about 1degree. Then someone woke in the middle of the night and pulled the tent door much wider open which dropped the humidity by 2% and the inside temperature by 0.75degrees, but the differential widened slightly.

I don’t know why the temperature varies so much during the night. Maybe it’s overall constant, but there are slight changes in convection currents that vary this. I should string the sensors all round the inside to see how it cross-varies.

It takes at least an hour for stability to resume when we leave the camp. Humidity rises as the temperature decreases.

Would the story have been different with a more porous tent fabric that could let out the water rather than one designed to be impermeable to liquids? If this was used we may have been able to raise the temperature inside the tent high enough to be clear of the dewpoint value, even though there is not much room below the 100% mark.

There should be a calculation of number of breathing and sweating bodies, the inside temperature and the and rate of exchange of air that provides for an optimal size and location of vent holes for the night. However, it’s difficult to find anywhere in the world that is this cold, humid and miserable for any experiments.

There are constant drafts around the cave which leave their mark in the rock formations. A set of barometers carefully synchronized, both outside and inside the cave, could produce an account of the total volume of the cave and its effective entrance surface area by modeling the flow of air molecules between these different reservoirs. This would tell you what percentage of the cave has been found. Experiments could be done on man-made tunnels whose dynamics are simple and volumes known. Higher frequency induced pressure changes might also be detected given that the bluefly is measuring at 50Hz.

Wednesday, July 13th, 2016 at 8:54 am - - Cave, Uncategorized

The weather turned caving, so I went underground two times. The first was to the shallow Balconyhohle (60m entrance pitch, then run around horizontal passages). There is a snow slope going up towards the surface that Andrew had a poke up.

Then someone showed me a demo of virtual reality using WebGL on a smartphone in a webpage, and I spent a couple of days coding the obvious idea I’d had years ago of putting all the cave data into a 3D model, using the GPS position and screen orientation to project it so that your phone acts like some kind of X-ray vision through the ground.


We used this to find a corresponding hole above the ground, which had a snow slope in it going down. It was a known hole in the database (identified by the metal tag drilled into the rock beside it) but with no record of exploration. Andrew looked at it the next day and couldn’t get down through. Later on he went underground again with a shovel and dug upwards as far as he could reach, but it still remained plugged.

Maybe if we rigged up some kind of a shelter over the hole to stop more snow falling into it, it could melt out in a few years. Something like some metal bars and planks of wood higher up to keep the new snow from getting out of reach of the sun so that the spring meltwater pours down and erodes away a bit of the snow plug each year.

Then, because I didn’t want to do much caving, I decided to go on the deep underground camping trip, which was far, far too deep with a lot of nasty scary rope rigging on the way down and up that kept me in a state of terror for hours on end. This is not as illogical as it sounds. Caving is horrible, and it takes many days for the memory of how horrible it is to wear off (like the memory of a very painful hang-over) before I am prepared to do it again. But once I’m down there I haven’t got a lot of choice.

Becka took her phone down to the camp (at -600m in Kraken chamber) and it took considerably better pictures than the fuzzy gopro I had.
There was a cross-over with the previous camping group, which is why there’s so many people in this image.

This is one of them starting up the big loose pitch out of the chamber, which begins with a 60m freehang, and then lots of rebelays on a blank rock above a soily bouldery slope that you keep kicking stuff down from. As a consequence only one person can be on the rope at a time and it takes ages.

The passages were enormous and we explored and surveyed about a kilometer of cave.

There were some surprising formations, including this pickled gherkin sized helictite with a drip on the end that never quite fell from it, because the mud was untouched below it.

When we three finished our two days and one night stint, the next team came down and met us at the tent while we were stoking up on food for the horrendous climb out (lots of pathetic whimpering from me) and overdosing on our salt quota (according to the packet, the instant risotto meal for two I ate contained 11g of salt). Somehow on our ascent one of us pulled the rope up after us and accidentally hooked it over an isolated rock ledge well out of reach, which meant that this team were trapped underground until the full-expedition rescue was called out owing to them being overdue.

Luckily, Becka and me were miles away in Griefenburg by this time, with her on her new road bike, and me playing in the low clouds. The sad thing was my favourite pizza joint in town had closed since last summer, and the restaurant we went to instead was a bit crap.

Back at the expo the next day, Becka went straight up the hill while I attempted to get in another flight. It didn’t go too well, and I nearly crashed off the ramp, probably because I’d kept the nose too high without a headwind to guide with wing position. I barely got away with it and haven’t dared look at the photos yet. Not good memories to leave this place with.

I calmed my nerves for a couple of days by coding the groundwindow application and getting to know something about writing GLSL shader technology. It’s pretty stunning, and it makes the phone quite hot from all the computational power.

Wednesday, June 22nd, 2016 at 5:46 am - - Cave

I cried at the state of the campsite in Austria when we arrived this year. It looked like part of the Amazon Rainforest — clearcut and still raining.

The plan is to be here for about six weeks, and it’s not looking like a great idea. Only about a quarter of the people have arrived so far, and even the cordoned off area is pretty churned up. I pitched my tent on a gravel patch by hammering in nails to guide the tent pegs.

So, to cheer myself up I did some coding, and wrote stl2png, a program to slice STL files directly into PNG images for use with an SLA printer.

This is an example of a generated slice of the two chamber whistle someone has been printing a lot of in DoES.

(The wifi internet for the computer is pretty poor around here in the campsite, and there is no mobile tethering allowed when you are abroad, so I am unlikely to get much blogging done for a while.)

Tuesday, July 21st, 2015 at 8:36 pm - - Cave

Top camp was still relatively empty before the hoards arrived for the third week expo. Two young ULSA (University of Leeds Speleological Association) cavers fresh from their bus trip from Leeds showed up and were easily persuaded to walk up the hill at 6am. We got there in time for Rachel to organize us into three teams and go do Balconyhohle into the area known as the Leeds Bypass. (Leeds people are gradually taking over this expedition in name and numbers.)


The team comprised of David, George and myself. Frank had found a new hole in the floor the day before and persuaded David to check it out. George and I went for a poke in the western extents in the direction of the Tunnocks cave (to which this one has not been connected yet).

On the walk back, I said to George, “You know that thin gap we saw in the ceiling back there? Do you want a leg up?”

“Sure,” said George.

He found a moderately large unexplored chamber up there. I didn’t believe him because there was no echo, but I had to squeeze through anyway to check it out.


We went back to fetch David who had so far only managed to push a big slab of rock over so it filled in Frank’s hole. He didn’t take any persuading to give up. We traipsed back to the drafting ceiling slot (tagged as “Question Mark 90b” in the database), pushed all our kit bags through, drills, tacklesacks of rope and ourselves, and began exploring and surveying it. Down one end there was a perfectly preserved dead bat spread out on the floor complete with wings and fur. David began drilling for bolts and putting in rope to get down the hole opposite to access the next level below.

We ran out of time and came back the next day.

Partway through the trip I finally got suspicious at how quickly George had been taking notes.

“Oh, I didn’t know you were supposed to draw a map. I’ve only been writing the numbers.”

David’s rigging had by then lead us down a rope and onto traverse line along a loose ledge above a bottomless pit to a proper passage.

I lay down for a nap while David sorted out some of the missing surveys. I planned to bodge out a map of the chamber above.

We carried on while David looked down the far end where there was a sandy slope with rocks embedded in the crest. He pushed one of them forward and it slid round the corner and carried on down. Back in the main passage with the high domed ceiling, George and I thought the world had ended with the entire cave imploding like a pile of boulders in a blender. I went rigid, unable to see any solid looking rock shelter nearby that I thought wastn’t going to burst into an avalanche.

When the noise subsided, David didn’t know what we were yelling at him about, so we stood him exactly where we had been and then went and pushed one of the other boulders off the slope so that he too could experience the amazing sound explosion.

As we were derigging the rope, a couple of other cavers were struggling through the crack to inspect our discoveries. “Go up in that direction,” I said. “There’s a perfectly preserved bat on the rock.”

They did.

Luke said, “What bat?”

I led him over and showed him where it was, now trodden on by a boot so that bits of wing and tail were spread over a wide area.

It was time to go out.

I came down the hill in the morning and typed in the survey data. It definitely doesn’t look right. There’s one huge rift passage which claims to coincide with an already known small passage. What a mess.

Tuesday, December 30th, 2014 at 2:27 pm - - Cave

This trip round the Lleyn followed on from last year’s Avoiding Nadilog by Walking in Wales. In retrospect nothing much happened. But it was exciting at the time due to the lack of planning and the risk of things going wrong.

Our white Xmas on Whistling Sands

Departure was delayed till the morning of the 24th because someone couldn’t possibly miss their 14th digging trip of the year in ODB. Anyway it was raining and we weren’t packed yet.


Sunday, December 7th, 2014 at 4:14 pm - - Cave, Kayak Dive, Machining

I’m going to do some other coding, now that I got this result. The code would fall apart if I touched it again.

Next on the list of things to do is clear out the vast quantity of rubbish left in the code, completely redo the subdivision loops and make the logic robust, apply it to multiple z-levels and plot slices, then make it test against edges and faces (not just points), and package it into a self-contained (but very slow) version of the slicer.

I don’t know how long this will take, as there are many other distractions available.

Monday, August 25th, 2014 at 1:53 pm - - Canyon, Cave, Hang-glide

I did get a very short canyon trip with an even shorter rope before expo was finished.


The canyon was called Salza Stauseeabfluss, and it went from the dam on the lake from Grimming. The rope was labeled at 80m, but no one had noticed it had been cut at 36m when they picked it up. We had to descend down the wall of the canyon in three stages off trees. We also got the walk out spectacularly wrong, and ended up clawing our way up a 60degree grassy slope in the dark.

This was on the same day I had a very nice 3 hour flight off Loser totally alone (due to west wind predicted) with a relatively low cloud base again, and tactically squeaked through the pass into the Bad Mitterndorf valley knowing that there was a good landing field there which I had used a week earlier.


Unfortunately every single field including this one seemed to be full of tractors cutting and bailing hay. Fortunately, a bird appeared and showed the way up to the clouds after 15 minutes of barely maintaining height.

That’s one of the lessons from the 50k Or Bust Book: both time and place matters. Use your arithmetic to know that a slow descent rate of 0.2m/s is only 12m a minute (or 120m in ten minutes), which means you can stay in the game for long enough for the next thermal to rise.

Because the clouds were low, I didn’t want to stray up into the mountains, and stayed close to the valley where the lift was scratchy. The predicted winds were never materialized and I belly flopped on my landing again.


Here I am looking to the Grimming. If conditions this year had been equal to last year I would have got beyond it into the Enns Valley and maybe around to the Dachstein. This is the big target.

The annoying thing about flying is how quickly a good flight wears off on you. I was already fidgeting the next morning as though I had achieved nothing the day before.

Becka said something very mean to me last night: “You seem a lot more dissatisfied with life since you took up hang-gliding again.”

This needs sorting out. My original notion had to be to treat hang-gliding like skiing, where you go abroad on holiday to the appropriate place and do as much of it as you can to get it out of your system, and then come home and get on with normal life. But it’s not quite working out like that.

The final flight in Austria was in rough conditions and didn’t go anywhere, but the landing was perfect, like I was on autopilot.


Then the weather became rainy and normal for Austria, and we were into the depressing phase of bringing things down the hill and tidying up after expo.

We got away from the campsite at 5am in the drizzle and caught the 10pm Dunkirk ferry to Dover, although I did insist we stopped at the McDonalds in Zweibrucken because that’s where the previous car stranded me for two days in May.


It was the highlight of the journey.

Saturday, August 16th, 2014 at 7:25 am - - Adaptive, Cave, Hang-glide

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.
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).
Here’s the outside view of Top Camp:
And this is the inside:
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:
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:

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.