maandag, april 16, 2007

Funky GPS data

Yesterday I did another mountainbike trip with my GPS. This is what (a part of) the map looks like:

Totally weird.

The red "scratches" going up north and (later on) west are at the beginning of the trip. Believe me, that is not the result of a wedding party the day before. I did follow the road.

More to the west the track is colored purple which corresponds to a speed of 84.9 km/h! I really want to believe that was the actual speed at that point but somehow I have my doubts about the correctness of that data.

The remainder of the trip followed a normal track with regular speeds. It looks like the first 10 to 15 minutes the GPS did not yet have enough satellites in view to provide high quality data. What a bummer: 1 hour and 15 minutes in the blistering heat doing one of the toughest tracks I know at a record breaking speed and what do I get: GPS data that sucks!

Since I log the raw GPS data I can only conclude that "real" GPS software (like TomTom or Route66) does some serious error correction to prevent you from freaking out while driving your car.

So the checklist for my next GPS-enabled mountainbike trip now is:
  1. Fully charged mobile
  2. Fully charged GPS receiver
  3. Turn on mobile and GPS receiver 15 to 20 minutes prior to departure

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