Thursday, June 26th, 2014 at 4:52 pm - - Adaptive

Just some notes on the serious work that’s still going on. This whole thing was supposed to take a couple of months. It’s run 6 months beyond the time I expected it to already because I had no idea how hard it would be. But this shouldn’t matter in the long-run as the code will probably be in service for 60 years if it works.

At the moment Adaptive Clearing doesn’t do any fancy links. If it can’t go nearly directly through the partially cleared pocket, it rolls off and does a retract to a roll-on to the next starting point. This doesn’t look great. Also, when we re-order the passes for better efficiency, we shred all the links that are any good and need another way of recreating them.

I’ve been meaning to write up something about how we re-order the passes for a year, because it’s a really simple trick. It’s unfortunate that it exposes this re-linking problem, so you don’t get the benefit.

I’ve disabled all the smoothing features that were getting in the way. The first priority is to make a path from the start to the end that avoids the uncut stock using the A-star algorithm which operates within the model of the area. This is how it currently looks:

We’re going to get lots of questions about how it passes on the “wrong” side of the previously cut path. The diagram below should explain why it is correct.

The real problem is that my linking path is going round the wrong side of the roll-off arc. It then has to back-track to find its way to its linking destination. Note how it zig-zags through the cells because re-smoothing is disabled.

The problem is that the cutting cycle skips out sections when there is almost nothing left to cut. But my re-linking motions spots this material and tries to avoid it. Since there’s not enough room to get round the arc on one side, it goes round the wrong way.

This small diagram shows how there is a lot less material there than it seems.

But still, it’s non-zero, and I don’t want to include a tolerance here. So I’m going to try and barge through the start of the linking motion and splice it in some way. Not sure how to code it yet. Things keep growing more and more layers of unexpected complexity. That’s how it goes.

Wednesday, June 25th, 2014 at 11:57 am - - Kayak Dive

Scored a bit of a hat-trick with a cave trip, hang-glide and dive in the same week. I had wanted to return to Rathlin Island this month, but following a quick trip to Cambridge a couple of weeks ago, we got invited to fill two spaces on a CUUEG trip to Pembroke with Celtic Diving on their enormous boat out of Fishguard.

I thought the best dive of the weekend was on Sunday on the wreck of the Dan Beard, one of the Liberty Ships.


Quite shallow, but clean with lots of metal bits, shiny brass, cogs, gulleys, two dark caves and a seal encounter.

This is a video edited from a couple of dives on the wreck of the Baron Ardrossan, which was more silty.

The conditions were sunny, but with a northerly swell, which limited the dives to sheltered bays where the visibility would not be ruined. We stayed an extra night and went for a kayak diving paddle from Abereiddy (absolutely packed with coasteering and sit-on-top kayaking activities), out to Sledge Rocks near the wreck of the Musgrave to experience the choppy waters and a strong tide, then back to land for a crap dive in the next cove, before up-anchoring and doing the Baron Ardrossan again, skipping Porthgain, taking lunch on an island before heading in to Abercastle and failing to find the blowhole.

It was a very long drive home, and I’m still quite tired. Should get back there soon as it has a lot of potential for more kayak diving to the east of Fishguard.

Friday, June 20th, 2014 at 7:35 am - - Hang-glide

First flight since getting back from Austria at Llangollen. It’s a purely enjoyable waste of my time, which is why I need to rationalize my workload to make room for some essential projects that are more productive and useful. (Note: The dirty secret in our society is there’s not much overlap between productive and useful work and paid work.)

The flying is just clean fun. Not at all scary now. In fact, I wasn’t scared to bomb out on my first flight when the winds were too light for even the paragliders to soar. I got off in a thermal, circled close to the trees to about 80m above take-off, and then drifted down to the bottom field where I discovered that following the instructions in the manual on how to land in zero wind actually works:

The traditional method of landing in light or no wind calls for a sharp, aggressive flare at precisely the correct moment. This technique works fine when done correctly, but it’s not easy to get the timing just right. Flare too early and you will climb, and then fall with the nose pitching down. Flare too late and you won’t get the nose up enough to stop your forward motion, and the glider may nose into the ground as you run into it from behind.

[We recommend] a combination of a “crescendo flare” and a run out of the landing… [B]egin your flare by smoothly accelerating the rate at which you push out on the bar. At the same time, draw one leg forward, put a foot down, and start to run as hard as you can. This run should be very much like an aggressive take off run – your body should be leaning forward into the run and you should be driving with your legs. The difference here is that while you are leaning into your run and driving forward with your legs, your arms are extending fully from your shoulders, pushing out, and what feels like upwards, on the control bar in an accelerating, “crescendo” flare.

Ah, that old “traditional method” phrase, which means “doesn’t work”. Must use that more often in other applications. Sometimes we use the phrase “the classical method”. It strikes a political balance of telling someone they’re completely wrong, but they shouldn’t feel ashamed they were wrong because everybody used to do it that way.


I packed up, began walking up the hill only to be given a lift by some paraglider who had driven down specially for me. Very kind. No one was flying yet. I fetched car, put glider on roof, drove back to top, carried over and rigged. The turn-around time was a little over 2 hours, which is about how long I estimated we’d need to wait on the hill for conditions to improve. I saw the one visiting hang-glider into the air (another Sport 2), and then got away myself.


There was a low cloud-base with very weak thermals, but I got there. I even busted through one layer of clouds into a gloomy gap between them and was at the top of the stack for most of the hour. It was dreamy.

Meanwhile, at work, we’re still mucking around with a year of improvements to Adaptive Clearing. I remember I was going to do a little write-up on how we do toolpath re-ordering in Adaptive Clearing. It’s very simple, but probably more worthwhile to do when I’m no longer debugging it some of the problems created by it. Things just keep getting more complicated.

Update: Here’s the quickly edited video.

Monday, June 16th, 2014 at 10:33 am - - Cave

What’s been going on since I got back from Austria? Mostly working (for a change), washing up, catching up on stuff.

After 18 months of agitation, I organized a Simultaneous Satellite Tech Summit in AD and managed to get 3 other people to turn up. The Tech Summit is a single 2-day conference between lots of the AD developers that takes place once a year in a hotel where everyone is flown in on expenses. Many of the talks are streamed on-line, so I thought it was a pretty obvious idea to hold a group watching event between the developers in England who were not burning lots of carbon to cross the Atlantic. This enables us to meet and interact in our local halls as people claim they productively do when they go to the real Tech Summit. After all, it’s more useful to form collaborations between the offices in the same country because it costs hardly anything to move between them and work on joint stuff.

This proposal brought out all sorts of flimsy arguments against it about how face-to-face meetings are so much better for forming relationships that don’t take account of the fact that we are software developers. We’re quite good at working together when we can actually access the same source code, and it is often the case that when we do meet physically on a personal level we won’t like one another at all. Stop arguing, the managers said. It makes our ears hurt. But how are we supposed to change things without arguing? You’d think a company that employs so many computer programmers would have some sort of a handle on the psychology of computer programmers.

I am not going to comment on the ScraperWiki newsreader event I went to in London, because I don’t know what to say.


Anyways, that’s just work. At the weekend Becka decided that I should go caving down Newby Moss Pot on Ingleborough as it was one of the ones she had not yet done from her favourite book: Not for the Faint-Hearted: 50 harder caving trips in Yorkshire.

I can’t say I learnt my lesson, so much as I should say: suckered again! It’s just a midge-infested fleabag of a cave with tight squeezes that lead to nothing of interest. Against everyone’s recommendation, I did it in a wetsuit, which meant I fit through the tight bits a lot better than when I have rolls of PVC fabric around me hooking onto every bit of rock in those wormhole crawls.

That’s enough of that. While Becka went on a quick trip down Penyghent Pot, I did a cycle tour of some of the Dales Hang Gliding and Paragliding Club sites over some of the region’s steepest passes.

I got everything from my waist down saturated with water walking up Cow Close Fell. I’m not sure any hang-gliders fly there due to the carry up and the bottom landing field in the valley being embarrassingly small. It looks like it would be harder work than Whernside. Whernside takes a SE-E, and Cow takes NNE-NE.


The other site I checked was Hawkswick which takes SW. This has a good track you could push a hand-truck up to the top and a good clean steep face to soar on.

I got tired of pushing my bike up the track and left it partly hidden in the bracken on the left. When I got back it was gone! Along with all my valuables in the pannier. That was a bad moment. I found it parked against the wall down by the main road. Not helpful.

I had no cream teas on the entire ride as there were none on the route. Becka and the others were already in the pub when I got back to the car in Horton.

Saturday, June 7th, 2014 at 11:43 pm - - Hang-glide

The trip back from Austria didn’t go quite so well. The alternator began to fail near Stuttgart, and we finally stopped at Zweibrucken when the exhaust got too noisy and fell apart.
The rescue by the local Autodienst adkaufmann was quick. After reconnecting the alternator (which had also mysteriously fallen off at the same time), we gave the car a push start and drove it round to their yard where the exhaust was welded back together. Unfortunately, the alternator was no longer charging and it was Saturday in Germany, so no car parts were going to be forthcoming till Monday. We were deposited into a hotel.
Zweibrucken was not very interesting, and our bikes were in the car. Tom read about the Felsen Wanderweg, so we caught the train to Rodalber and walked it, eventually finding the 40m deep sandstone cave.

The car repair bill was £300, and then another £250 back home in England to get the exhaust fully replaced as they’d completely knackered it. Additionally, the car has been deemed unacceptable by certain individuals who weren’t even on the trip, on the basis that nobody else’s car ever goes wrong like this, ever. (This isn’t true, but facts don’t matter.)

So, setting that business aside, here are the costs and benefits from my holiday.

There were 11 days available in Austria from 20 May to 30 May and I flew on 7 of them to clock up 16 wonderful hours and 31 minutes flying time over 9 flights.

We drove a total of 2600 miles and spent £300 on fuel. Ferries cost £110, highway tolls cost £40, food was £191, camping was £165, flight tickets, taxis and toll roads were £62, and I bought £26 worth of maps.

To cheer myself up, here is a short video of the climb out from my duel with the dual glider.

Saturday, May 31st, 2014 at 6:21 am - - Hang-glide

May 29 was predicted to be a poor thermalling day. I caught the taxi up with the expectation of making two or three flights in the day just for practice. The take-off field was crammed with gliders for yet another German hang-gliding competition. No chance of getting off early. The competition task was short: a speedy zig-zag across the valley and then to the landing field.

By the time there was enough room to get to the front, there were all sorts of antique gliders being set up, including an Airwave Calypso, which is the kind I flew when one belonged to the Bristol University Hang-Gliding Club in 1991. Imagine the days when almost every British university had its own hang-gliding club. It boggles my mind.


There were two tandem gliders preparing to take-off. These tend to be large, inefficient, slow-flying gliders that waft around on big sails. The co-pilots were both blond girls with no fear. Here is one of them being shown how they will run down the ramp without tripping over.


I stopped prevaricating and delaying my own take-off, and finally got in line ahead one of the tandems. After bimbling around above the trees and generally being useless, I noticed that one of the tandem gliders was out-thermalling me. This got me very angry. If I was going to be beaten by a crappy tandem glider, I might as well give up on this whole game. There is no point in me buying all this fancy gear if I cannot go places.


I followed the tandem on its circular course and was soon above it. The tandem continued to skim past me at an alarming angle. Now it was a matter of survival that I should stay in the thermal successfully and keep above it. My brain was switched on.


After another ten minutes I was up and chasing the clouds. This is where I wanted to be. Unfortunately I had no gloves and was wearing only a thin fleece. The parts of me outside the harness were chilled, but my main body was warm. The harness is tight and sealed. It feels like being in a big bear hug with barely room to wriggle my legs or torso. The pressure is calming and reassuring.


I journeyed east as far as Goldeck, watching from cloud base the procession of rigid wing gliders cross the lake for their turn point and then race down the valley to the landing zone. The thermals failed to materialize on several sun-drenched ridges, and I was half-way down the mountain and barely maintaining altitude before turning back. There was no chance I would make it to Griefenburg. Unless…


That was such a joyous thermal. It did not feel like I was flying, so much as dancing on a big soft balloon. I looked up and watched the black nose of my glider gyrating. I love my glider. I did not want to pack her up after I landed in the field.

Friday, May 30th, 2014 at 5:24 pm - - Hang-glide

We’re bored. Let’s go somewhere new. The car was packed and outside the Griefenburg Fliegercamp gate overnight and we left at 6am for Mayrhofen, arriving in the main valley landing field just in time to befriend another intermediate hang-glider who was wondering how he was going to get himself up the hill and his car back down again.

We were exactly what he was looking for, and his glider was on our roof-rack within seconds of my making the suggestion that he show us the way.


His usual take-off below the road at 1600m above the valley seemed improvized. After you set up and get into your harness, you sidle across the slippy grass until you are looking down a gulley. Then you step backwards up the slope as far as you can into the weeds to make your run.


For the first time ever I made a huge “WHOO-HOO!!!” on take off. I don’t why, but it felt real good. The video wasn’t on, so there is no record of it, or of all the spirals and turns I did on the way down through the silky smooth air. Now I fully realize that the glider cannot turn when it is coasting at minimum sink-rate. I became more sensitive to its need of speed.

As usual, the landing was not visible from the take-off, so I had to follow my friend down to the field. It’s bordered on all sides by high tension power cables. “They’re pretty useful because they help you judge your height for your landing approach,” he said.


Tom and I pitched our tent in the landing field and went exploring for canyons by bike. Mayrhofen is at the junction of four valleys, only one of which provides a way out. The two canyons I had details of were in flood, but there was a third called the “Blue Lagoon” that canyon adventure tours used. We didn’t know where it was, but by studying the photos in their brochures we eventually worked it out.


The deal with the camping is that you should eat dinner in the local Gasthof. No problem with that. At 6am we drove up to do the Blue Lagoon canyon. Just as we got changed into our wetsuits, it began chucking it down. Not knowing how the canyon would respond, we jacked. The rain chased us. Pretty soon it was raining everywhere we went. After two hours, we were as miserable as if we had endured it for two weeks. The bunny rabbits were huddled under a camp table going soggy. Maybe this would be a good day to work, I thought. What I need is an internet cafe.

For a completely touristed town like Mayrhofen, how can it be that there are no coffee shops with power sockets and wifi? I thought the whole world runs on these things. We drove to the next town up the valley and got unnecessarily wet wandering around there.


There was nothing for it but to set up Cafe Berlingo for that smooth purple smell of burning meths in a trangia. Electricity supplied by an inverter. I did some Java programming with Tom on Tunnel to visualize file layouts of survey data. I should finish what we started at some point.


There was a break in the rain overnight, so we were up at the canyon at 6am again making tea in Cafe Berlingo before setting out on the double. If this canyon wasn’t flooded by now, it was never going to be. There were pools, jumps, two pitches, and we scrambled out to the road from the wrong place.

Then we were off back to Griefenburg, via the unnecessary toll-road pass (as disclosed by the map of Pingzau we bought), an unnecessary paid parking stop at the Krimmel Waterfall (we irrationally baulked at the 3 euro charge to get in), a visit to a potential flying site in Hollersbach, and a stupidly long drive up a mountain to a monorail toboggon ride that was closed. Frauenbach Canyon was also inspected. It was still gushing forcefully.

It was sunny and lovely in Griefenburg. We got our old camp space back.

Sunday, May 25th, 2014 at 6:54 pm - - Hang-glide

Like I was trying to make a very lame joke about the 80 Germans hang gliding competitors getting their gliders spread out on the deckchairs before the english person has woken up, but their launch window was 11:30am, which meant they all flew off and got out of the way before I was even thinking of being ready.


I wanted to wait till the middle of the day when thermals were more reliable and required less expertise. Fat lot of use that did. Bombed out slowly in 44 minutes.


I was the only hang glider in the bottom landing field. What an idiot. I packed up quickly, carried it over to the taxi rank, and then waited for an hour for a few more people to fill it. I bit my fingernails till they bled and texted frustrated expletives to Becka on the phone. The competition pilots were starting to land from having completed their 100 mile round trip task of the day. I was nearly crying. Back up top at 4:20, I was the only glider rigging in a completely empty field. Have to slow down and not make an assembly error. That would look even more stupid.


Much happier. Straight up to cloudbase. Then, as the evening shadows set, I found some very weak lift on the south side of the valley and stayed up till 7:45pm as the last glider in the sky. No one seemed to care or notice. Not even Tom who could have taken a picture of my crappy landing had he looked up from his book.


In the morning we decided to go do Frouenbach Canyon, rated as the best in Austria. One look at the terminal cascade and Tom said This is not going to happen. Must be the meltwater from the snow as there has been no rain.


I went up, watched all the German pilots take off, then went at 1:20 and bombed out even more spectacularly through horrendous turbulence, not even making it to the landing field. Luckily one of the race organizers mistook me for a competition pilot and gave me a lift back to camp after telling me that I was “a very bad man” for landing in the field of uncut grass when I should have been up high.


Here we go again. Straight up to cloud base and over to any mountain peak I chose. Is it me, or is it normal to be stunningly crap half the day, and then do brilliantly at other times? No one else seems to have this.

Then, later, it rained, and got ugly. I headed for the large backup field on the other side of the river and got picked up by a gust on the base leg of my approach and dumped into a ploughed field. One of the German pilots there came and shook my hand, for marking a thermal for him that he desperately needed to complete the competition task. Didn’t have anything to say about the landing. The competition only is all that matters to competition pilots.

Friday, May 23rd, 2014 at 1:56 pm - - Hang-glide

What a surprise. As soon as I get some hang-gliding in, I can’t care less about anything else. All those plans I of doing work and other productive things during the majority of my time I would spend not flying have gone out the window. Look, man, I have just spent three and a half hours spinning about in the air currents just getting up to the tops of the mountains at the very limit of my skill. Unless the house has burnt down and Becka has been kidnapped by pirates and held to ransom, it will be difficult to hold my attention. I am in a dream. I am also 1000 miles away and not coming back until June.


Meanwhile, there are Euro elections. I’m not sure why the green candidate in this Bad Aussee election poster decided to use his zombie impersonation poster. It’s all going to shambles. Democracy in Europe: we just don’t deserve it. At home we have the UKIP clowns, and the Conservative Party copying every crazy policy they can from the UKIP clowns in the belief that it will help them in the polls, when in fact people are not voting for the policies anyway; they are voting for the clowns, because at least clowns are honest. The mainstream politicians at the top are just in it for the ride, like I am with my flying. They don’t have any policies which they actually care about which, if delivered, would mean they would find something better to do with their lives. No one supports the Green Party to get power. Something must get done within the system or it’s all going to hell. Got any better ideas?


I had a second flight off Loser and went straight down before catching a thermal off the town that I followed right along up the valley in a sheared coil without much upwards component.


At some point I decided I was getting a little to far downwind from the landing field by the lake, and made a dash for it.

This was supposed to be a good thermalling day, but it wasn’t. I did have the fortune to reread the chapter from Burkhard Marten’s book about how to core a thermal, and realized I had completely misremembered it. I thought it said turn tight in strong lift, and turn shallow in weaker lift. In fact, it’s the other way round: as the lift decreases, you turn tighter so that you can quickly go back and re-enter the strong lift, but while you are in strong lift you delicately search for areas of even stronger lift whilst also opening out into an efficient wide turn that makes the most of the lift area.

Anyway, it’s starting to work for me. I have learnt to love circling. I used to think gliding was boring, like skiing, because all you do is go left, go right, or go straight and on and on and on. But actually, doing the circle is the pattern. It takes about 10 to 20 seconds to execute a circle, and the shape of that circle is the expressive force in terms of interacting with the invisible thermal lift zone, which is itself circular in nature.


I got rather dreamy in the air as I got into this notion. Then I saw a shadow on the ground that wasn’t mine. It was from another glider. I hadn’t been paying attention to what else was in the air for a long while. The pilot waved to me as he spiraled up past to a cloud that I couldn’t reach. Though it feels good, I am not as proficient as I should be.


Meanwhile, my co-driver, Tom, has been entertaining himself with some long cycle rides to check out the canyons. I promised we would descend a couple when I’m not out flying. Unfortunately, there’s a minor flaw in this plan: usually it’s the thunderstorms and rain that stops flying, which is also not the right time to be going into any canyons.

Tuesday, May 20th, 2014 at 6:55 pm - - Hang-glide

We drive all the way from England to the Loser Plateau only to find that the local Austrians had left their ramp full snow! Lucky we went up the hill early as it took me and Tom 2 hours and a borrowed snow shovel.
To be fair, it all fell in the last three days, after a winter of no snow, so it’s only come when nobody wanted it. Then the wind blew from the back until 2:30 pm, when it changed, and I took off.
Three hour flight with already very tired arms, just getting to grips with how to thermal properly. Landed on my face in the usual field behind Hilde’s. Time for bed now after one bier that the bar because Tom forgot to buy any in the supermarket on the way back.
One good thing, was my magic GPSSMS android app thing worked and successfully texted Tom with my position every 20 minutes when I was not too high. The secret function to make it work was WakeLock.