Modern Athlete Magazine Issue 128, March 2020 | Page 30

OUT OF
THE By BOX
Norrie Williamson
GOING THE (RIGHT) DISTANCE
I still often see runners complaining about the accuracy of course measurement when they finish races and their GPS
watch says the course was slightly long, or sometimes slightly short, but there are many factors at play here that runners
do not understand – and the courses usually are, in fact, accurately measured.
This article was originally published in our February 2017 edition, and we are
republishing it by popular demand, because the debate about GPS accuracy
still regularly pops up on social media after nearly every race!
G
PS can be extremely accurate: This was clearly illustrated in 2006 in Beirut,
Lebanon, when I was measuring the marathon and saw the destruction
inflicted in the Israel-Lebanese war, where the outbound section of the
highway was taken out by a missile strike, but the inbound section left intact.
Military GPS is that accurate, but that is a far cry from the units we wear on our
wrists for running, as I have found in years of course measuring – and there are
obvious reasons of safety why military standards of GPS are not provided to sport
or even driving units.
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ISSUE 128 MARCH 2020 / www.modernathlete.co.za
If you download the data from your GPS running watch, you get a vast amount of
information that appears to be highly accurate. Take for example my screenshots
below of the Athens Marathon, which would suggest the course is 575m too long.
However, closer inspection reveals that the runner is apparently running just off the
side of the road, and that right turn at bottom left has me creating a completely new
road before running down the side of the park. Now keep in mind this is me running
as one of the team that actually measured this route for the 2004 Olympic Games,
so I know where I actually ran, and I know how to take the very shortest but still legal
route on the road – yet my watch gave me 575 metres over the distance.