GPS Logging at Epping Forest North

At the Epping North event last Sunday, I ran with a GPS logging unit, for the first time. It logs my position every second, assuming it has a fix on at least four satellites. l Considering the device is not very sensitive, and I was wearing it at waist height, I am quite pleased with the results. The only section where the track didn’t come out well was the first part of leg 1 to 2.

It is difficult to line up the track with a scanned map, however the excellent RouteGadget software makes this easy for you – you mark known points on both the track and the map, and it does the rest. The result is not perfect, however if you look at my GPS track for the race, you can see both where I spiked the control and where I fumbled near the end – as well as my big mistake, which was the latter half of leg 1 to 2.

My GPS track for the 8.29km Brown course is here.

2: Big mistake here, I swung to the right, heading to Control 7. Despite realising this at the control, I was still unable to close in on Control 2, and overshot – you can see all of this on the track.
5: Confused by unmarked yaped path, went around the control.
12: Low visibility, turned back too early, thinking I had overshot.
16: I came off the path too early here – I lost reception here so you can’t see this on the track.
21: Swing too far to the north, corrected my mistake early on.
22: Overshot.

The others, as the track shows, were spikes. 🙂

I’m hoping to run again with the GPS unit. I’ve ordered a more sensitive unit, which I’ll be able to use with my mobile phone as the logger, in the new year once some bugs have beeen ironed out.

Despite the errors you can see on the track, I went on to (just) win the race. Full writeup of this event, and of the preceding events this month, including the Oxford City Race, to follow.

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4 Comments

  1. Nice. Just curious – how many “known points” did you use? I usually use about as many as I had controls (points to force route visit each circle center and some extra points for longer legs.

    Do you think additional tools for removing/editing individual points would be useful?

  2. I used around 8 known points.

    I would have done one for each control – except that every time I added a blue point, the red line got very distorted, sometimes to the point of being unrecognisable as the route, and sometimes all the blue points would get “reset” and the whole red line would jump up above the top of the map.

    So the process was very time consuming and I gave up after about 8.

    But despite that bug I really like the tool – I was thinking of having to do some complicated transform, rotation and shear of my route as a transparent layer above my map, using the “known points” feature is so much nicer!

  3. That bug was fixed months ago. I guess you still had old buggy applet version (from cache). I think it will work much better next time.

  4. Thanks Jagge, indeed I mmust have been using an old version of the applet in cache. It worked great when I marked up my Hindleap Warren route today – working on a proper base scan rather than a photograph of the map also helped a lot with the orthorectifying.

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