Mark Neal reported some nice data in the thread Another GPS test.
I have just analysed 26 runners' GPS results for a half marathon.
The results show a statistically nice looking normal distribution shape, averaging 2.2% long with a standard deviation of 0.8%, some 25 to 50 times worse than the Calibrated Bike of the course measurer.
These runners' GPS results look about twice as bad as Mark Neal's smaller group - but it is a different course and a different sample of runners.
I have written up an account for public consumption here. Comments are welcome before I link it into the website where the GPS wearers were publishing their complaints.
Mike Sandford -
Measurement Secretary South of England
UK Asssociation of Course Measurers
email contact m.sandford at lineone dot net
Good data Mike.
I suspect the reason these runners ended up with longer measurements than those in the race I studied was that the number of runners in your race was probably much larger. This may have forced the runners to go wider around turns and not be able to cut tangents as well, thus adding to the length of their run even more.
In my study we actually ran the courses later wearing Garmins and being very careful to follow the SPR, and we got readings just a few meters over the actual distance. This indicates to me that most of the reason runners get long measurements is that they aren't running the SPR. The big surprise for me was how MUCH they aren't running the SPR.
The conclusion is that when runners tell you the course they ran was long, you can now agree with them. The course THEY ran, was long.
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