GPS

Getting from A to B on your own two feet may be becoming a lost art. Not just being able to follow a track and persevere when you think you are lost, but also crunching the kms, one after the other, to reach a distant goal. At the end, you’ll want to know where you’ve been, how far you’ve walked and what time you did it in.

Tracks change, and some are becoming lost as fewer people walk, or even know, them. I was intrigued by the idea of mapping tracks on Google Earth when first walking the European Long Distance Hiking Path E1 in 2008. At first, this was a matter of mapping a track with the help of the sketches in the literature; later I recorded intersections on a digital voice recorder; finally in late 2009 I bought a GPS tracker, a RoyalTek RGM-3800. Granted, the technology – in terms of what the device delivers – is not particularly sophisticated, and the software’s English is miserable (“waiting for get data…”), but it works. You get your track, and then you can try correcting it in GE.

The problems in GPS’s lack of sophistication lie not with GPS as such, but in the even lesser sophistication of some reviewers of these devices at Amazon, who believe:

• The device should be accurate down to the centimetre and that it is broken when GPS’s ± 10 m accuracy sometimes results in points that are 20 or 30 m from where they should be; and/or
• It should be capable of tracking a car in a curve without cutting the corners…
  

No, the real problems lie in finding a way to work with the data in GE.

And here we have yet another task for the busy programmer. Yes, I have made my peace with GE, and GE has given me back track points of visible (i.e. editable) size. And of course, the technology has to be taken to the utmost limit. I know that two readings a minute will record a tramping track at a reasonable resolution; but one reading a second – when averaged over 30 seconds – also gives a reasonable estimate of altitude, the most problematical of the measurements, as well as average position in that half minute. This altitude data combined with the SRTM (Shuttle Radar Topography Mission) data set available here gives the best possible resolution in three dimensions from publicly available sources.

Alpine Crossing per GPS. Andermatt to Osco (Switzerland). Altitude colours (from SRTM): blue are the mountains, green the valleys

To record the North-West Circuit at this rate, the memory chip of 64 MB will be just sufficient. Since this technical detail was unavailable in the manual, I had to switch the device and run it until the memory was exhausted (and recorded for more than 120 hours). And there’ll be plenty of batteries, because as to date no solar charger could be found with solar cells giving 150 mA current. But a pair of batteries will last for 10 hours of recording (at least eneloop brand), so that should be enough for the project to succeed.