zaterdag 7 juli 2012

Postman Pat Psychogeographix first Carto-Chaotic results

Overlay of four GPS traces of one of my three postal rounds, click to enlarge. The overlay was made manually by stacking the individual tracings for *artistic* effect. This round consists of two distinct parts. One part is a collection of five streets in the top left corner, the second part is at the right. You can clearly discern the difference between me biking back and forth and me delivering on foot. 

Even though I am recording points at maximum rate the device fails to keep up with my meandering through broad streets and garden paths.The trace below, from my round in Garden Village shows what I mean. Here the streets are all completely straight and nearly every house has a front garden and from the trace you would expect to see this, but instead the lines haphazardly average out as lines on a polygraph. Maybe I should slow down. Now You understand why things could have been worse.

3 opmerkingen:

  1. Great series of posts, keep them coming!

  2. GPS is an invention of the US army and, as such, is deliberately imprecise in order to avoid it being used by other countries to accurately target US military facilities (the US army uses the version without the added errors). That's why botanics researchers doing phytosociological studies (which require exact geographical positioning) always measure GPS coordinates three times: the mean of the three values helps them define the most probable position.

    Keep up the good work !

  3. And probably there are some random errors involved also. If you leave your GPS recorden in one place you will see that it drifts around. I think this is caused by limitations of the receiver electronics and rounding errors in the position calculations. There should be a lot of detailed analysis available on the internet (but I'm too lazy now to search).

    Wilfried, I'll send you a Vinex booklet that contains an interview with a postman.