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Title: Does anybody use a GPS lap timer? Post by: Cider on December 05, 2008, 07:45:26 AM I like the idea of a GPS lap timer like those offered by Starlane or MaxQData, but I'm too cheap (and too slow) to spend $500-$1000 for one. However, I was playing around with a 1Hz data logger that my wife bought for her bicycle, and it made me think that a cheaper DIY version is plausible. I drove around the neighborhood a few times to get some test data. Then I hacked together a quick program that defines a start/finish line (just two coordinates), interpolates intersections from the GPS data, and calculates lap times. Crude, but it appears to work. Adding sectors, braking/acceleration zones, plots, KML output for Google Earth, etc. is all pretty straightforward. Also, I think it's possible to calculate lateral acceleration from the GPS data as well.
1Hz sample rate isn't very good, so I ordered a 5Hz data logger online for ~$85. I won't receive it until next week, but I was comparing it to the loggers on MaxQData's website, and it looks like the same hardware (they want $400 for it). In any case, has somebody already written software to do this sort of thing? If not, I have a new winter project. Title: Re: Does anybody use a GPS lap timer? Post by: Cider on December 06, 2008, 02:52:07 PM I spent some time figuring out how to find intersections of great circles to see how close my simplistic linear interpolation was, and it turns out that the distances are so small, that the numbers are nearly identical. I guess I'll keep plugging away at this.
Title: Re: Does anybody use a GPS lap timer? Post by: froggert on December 07, 2008, 02:56:18 PM i have a starlane with track mapping and like it a lot. i wouldn't get a gps lap timer w/o the track mapping, as it's the ability to see your lines and speed at any given point and being able to compare it other laps that makes it worthwhile.
Title: Re: Does anybody use a GPS lap timer? Post by: gm2 on December 07, 2008, 03:08:10 PM i have a starlane with track mapping and like it a lot. i wouldn't get a gps lap timer w/o the track mapping, as it's the ability to see your lines and speed at any given point and being able to compare it other laps that makes it worthwhile. really want one of those, for that very reason... Title: Re: Does anybody use a GPS lap timer? Post by: Cider on December 07, 2008, 06:05:41 PM A friend gave me some Starlane data files and I played with their software for a bit. I really like the RPM data that they include. Their mapper is also nice, but I'm going to roll my own.
Title: Re: Does anybody use a GPS lap timer? Post by: Cider on December 08, 2008, 06:18:41 PM The GPS logger showed up in the mail today. Compare it to the MaxQData MQGPS-TraQr (http://www.maxqdata.com/MQGPS.htm (http://www.maxqdata.com/MQGPS.htm)). Looks like the same thing to me, only $300 cheaper. I have to charge it up before I can play with it, but I think this will be a great low-cost solution.
(http://farm4.static.flickr.com/3208/3094485962_14682355d4_o.jpg) Title: Re: Does anybody use a GPS lap timer? Post by: Munch on December 19, 2008, 11:43:04 PM Keep us posted with your results!
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