Jez Higgins

Freelance software generalist
software created
extended or repaired


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Tuesday 28 May 2013 The Forest Road Reader, No 58

Michael Vaughn on Test Match Special : Whitby can be just like Barbados.

Initial tests with the CycleStreets Android app this morning were good. The particular problem I was having trouble with was the thorny but essential one of working out if you've started freestyling and gone off the planned route. Given a line between two points you can work out the cross-track distance (ie how far to one side or the other of the line you are) and the along-track distance (ie how far along the line you are). Those calculations are straightforward. However, they don't tell you if you are, in fact, off the end of the line bounded by those two points - you've not yet reached the start, or have headed off past the end. You have to do some geometry to work that out, which was one of the things I was having trouble with. It's also a bit tricky when the route you're following isn't straight. Not all roads are Roman, and even Roman roads have the odd corner.

Change of vocation

A route, plotted by CycleStreets, is made up of a number of segments and a segment might be described by any number of points. As you move around the phone GPS tells the app where you are, it does some sums and tries to work out if you're still more or less on track. Up until yesterday, I had a problem which meant that you'd be trundling down a perfectly straight bit of road to suddenly be told you were off track and the route needed replanning. That's sorted now. Because curved routes are approximated by a series of straight sections, I also realised it's possible to be, momentarily, off the end of one sub-segment and not yet at the start of the next sub-segment. In that situation, the app now also remains calm rather than replanning.

Shelves at the Birmingham Archive

Having had a fairly extensive wander around this morning and again this afternoon, when I stayed on track it told me where I should be going and only when I purposely went off-piste did it reroute. This is good. I am pleased.


Tagged cyclestreets, cricket, and birmingham


Jez Higgins

Freelance software generalist
software created
extended or repaired

Older posts are available in the archive or through tags.

Feed

Follow me on Twitter
My code on GitHub

Contact
About