O.O'Brien

I took my GPS on today’s orienteering event, and again it performed generally well.

I’ll write more about the event soon, but for now, here are the “signatures” of three of my mistakes today, as captured by GPS and shown on Google Earth (in an area with low resolution satellite imagery, which is why you can’t see the individual trees.) Note the scale – it’s only about 70m from the left to the right of the photo.

Control 10, approach from North: The Undershoot – Stopping too short, thinking you’re on the wrong line, head away, look back, oh, there it was in front of me after all.

Control 13, approach from East: The Lack of Attack Point – Slightly off line, no plan. Realise I’ve gone too far, double back but don’t know which way to turn, so go the wrong way. Then look at map and realise what’s going on.

Control 23, approach from West: The Overshoot – Misread map, path goes on further past the control approach than I thought – so I just turn off too late. Realise and turn around, there it is, back up the spur.

Here’s a map showing a dot for each second of the race – when the GPS receiver was able to get a fix. The start is the big green blob on the top right, the finish is the yellow blob to its left. (The trail to the north of these points is the walk to/from the assembly.) The general layout of the course is an anticlockwise loop – not a figure of eight.

The only section where there was no signal for a significant amount of time was very near the beginning – there are several gaps here. Once climbed to 170m, the signal remains good for pretty much the whole way round.

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.