In the last posting I mentioned that I made the routes in MoNav more persistent:

As a consequence, I’ve just written some code that detects whether the vehicle is still “on track”. The route only gets recalculated in case the vehicle left it for more than x meters. This makes the route much more persistent and will cause far less headache than the previous approach.

Since the GPS position is always a bit inaccurate, it will almost never be exactly on the computed route. Instead, it will aberrate a bit from it. What you want to achieve is to detect whether the current position still is either near the route, e.g. left or right of it, no more than x meters away and still in direction to the planned target, or in the opposite direction.

First the computed route:

This hardcopy shows a small deviation in the opposite direction of the route. MoNav does neither force the source indicator to the route’s polygon nor does it recompute the route, as long the distance is still near the originally planned route:

In case the position was in direction of the route, but somewhere in the houses nearby, MoNav will determine the nearest position on the computed route, shorten it accordingly and show the source indicator at the startpoint of the shortened route instead of somewhere in the houses nearby:

IIRC I’ve seen such a feature as an option called »Lock to road« in commercial routing software.

The problem seems to be easy to solve, and actually, it is. However, it requires some linear algebra (aka vector maths). Quoting lbackstrom:

Many TopCoders seem to be mortally afraid of geometry problems. I think it’s safe to say that the majority of them would be in favor of a ban on TopCoder geometry problems.

You can find a couple of places with solutions using a search engine, and the example of Rod Stephens finally did the job for me after porting it to C++ and adopting it to my needs (thanks for the kind permission to use it BTW).

So what is this posting all about? Remembering my school days, many pupils disliked maths, especially word problems. Which is a pity. The world is full of issues solvable by applying a little math, while people refrain from solving them due to some aversion. Got interested? Great.

Maths have been invented to better describe the world we live in. And computers executing maths help to make the world a better place, day by day. Be the one who converts maths into useful computer programs. And you’ll feel good during the Xmas break :) .

Gudereit LCR Trekking Series bicyle

During the last four years my biking trips almost completely took place in the upper Rhine plane, occasionally touching the borders of the Vosges Mountains or the Palatinate Forest. I tried to avoid inclines, as my bike with an 8 gear Shimano hub was not the best companion for such trips.

Last year I had the opportunity to try a mountain bike at the Kaufungen Forest. I was impressed by the possibility to climb steep tracks and trails slowly but steadily in case you have enough gears at your disposal.

The 14 gear Rohloff Speedhub provides almost the same gear ratios as a 27 gear derailleur. This appears non-obvious at a first glance, as the latter one provides nominal 27 gears (3×9). But actually some of the gear combinations cannot be used due to the strong offset, and some rations may occur twice, so the amount of actually usable gears decreases rapidly (obviously I am not really savvy concerning this subject). Meanwhile you can thus buy the first mountain bikes with a built-in Speedhub, and it is obvious that I needed to test mine in a hilly environment.

I took the train to Oos (126 meters of altitude), crossed the inner city of Baden-Baden, headed towards Lichtental and Oberbeuern and chose the tertiary road to the mountain pass »Rote Lache« (690 meters of altitude), crossing Gaisbach and leaving Schmalbach on the left hand side. At Rote Lache, I enjoyed a lengthy lunch break (heck, I had no breakfast). This is the valley of the river Murg as seen from Rote Lache. The village in the foreground is Bermersbach, the village in the background is Gausbach:

Murg valley as seen from Rote Lache

I did not choose the tertiary for the downhill part of the trip. Instead I choose some tracks which I intended to map for a long time now. Here are some pictures of the tracks, in order of their appearance:

Rote Lache - downhill trail

Rote Lache - downhill path

Rote Lache - downhill track

Here’s a picture at the end of the valley I crossed downhill, showing some of the typical traditional hovels:

Black Forest Hovels

After I hit the valley of the Murg in Weisenbach (228 meters of altitude), I continued the »Tour de Murg« where I stopped yesterday due to some raindrops. I entered the train back home in Gaggenau, omitting a visit in Rastatt. Here’s today’s trip:

Despite the forecast today’s weather conditions have been excellent. It was a warm late summer day with some clouds, and I enjoyed every single minute of the trip.

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Here’s one site note concerning the battery lifetime of the N900¹²³. I forgot my additional batteries at home. Thus I set both the N900 as well as Mappero to use the screensaver as often as possible, and I tried to use the N900 only in case I needed to know whether I’m still on the right track, to record some waypoints every now and then and to take a couple of pictures. Mappero was constantly logging a GPS trace, even when the screen was blanked. The battery still had about one half of its capacity available after about 7 hours, and I think this is worth mentioning.

More postings will follow. But the frequency will surely be less than before.

Korg Z1 - Parameters of the Bowed String Model

I’m currently reading the master thesis of Henri Hagenow (2001). If you are capable of reading german and interested in that matter, it’s a very interesting read (attention: some maths ahead :) ). It gives me a much better understanding what happens inside my beloved Korg Z1 synthesizer.

In the next live, I’ll become a physicist and write cool audio software.

If you haven’t noticed yet, a workshop about mapping and using public transport data will be held on Sat, 2009-05-16 at Scheffelstraße 17a, Karlsruhe, Germany. Anyone interested is invited to drop by, though “registration” is appreciated.

Eric also played an Roland XP 80 and the guitar.The Theremin was connected to an guitar effects processor and he used a lot of reverb and delays. The Theremin was manufactured by Big Briar, the new company of Robert Moog who originally invented the analog synthesizers in the middle of the last century.