I was talking to my old man about running and in particular my 10k race in London, which had a chip timer. Now.. My watch, which is a very reliable watch, said that I'd actually run 10.4 km and that I was running.. let's say.. 5 min 20 sec kilometres. But the chip timer, which can't be wrong.. had me at 56 minutes.. so something like 5 min 35 sec kilometres...
Are you still with me? My official 10k time was 56 minutes, but my watch said I'd actually run more than 10k. I just assumed my watch was wrong.. but is it? Was I actually running faster?
Honestly, this isn't about me trying to claim that I had run it faster 😂 (it really is 🙄) .. But my father just said.."Well, it's obvious, over the course of the race, running to the water station or overtaking people, you've added 400 metres over 10k"
I was aghast at this 😲 Could this actually be true? It made sense to me, taking corners, running left to right on the road.. could runners be running longer distances than others, and could it be as far as 400 metres in a 10k race.. a whole running track?
I know in the marathons there’s a blue line that is where the course was measured to be exactly 26.2 miles... but obviously the road is a lot wider and there are a lot of runners with us mere mortals... while Messrs Kipchoge and Farah can easily run the blue line for an exact distance, the vast majority of runners will run over the distance, and it’s even possible to run under it but this will make some corners tight enough to slow an elites time down. I’ve heard that this means the average marathon runner may actually be running more like 27 miles, so there would be a theoretical equivalent of a 10k runner would be running 10.25-10.5k
Depends on the course... just been reading, if the marathon was a circle and you ran 3ft outside the blue line then you’d only run 17 feet too far... in the major marathons you’re probably running more than 3 feet outside it most of the time and it’s not a circle, which would amplify the issue.
GPS accuracy will also vary... maybe you start in the open with +/- a foot of accuracy... run under some trees in the summer and it may go +/- 50 feet at times, same with tall buildings around you.
Yeah... my walking GPSr tells you the accuracy range... sadly my watch doesn’t but I believe they would be similar, if anything my handheld would be more accurate I think. There’s an app for phones that can make it show, but I don’t even know if it’s possible to see on the watches... maybe there’s a diagnostic mode it can be set to?
The walking one also has a screen where I can see where the satellites it can see are and which it is using... on the top of kinder scout I get great triangles, city centre Manchester I often get 3 in a pretty straight line and then the accuracy really sucks... and my phone becomes more accurate at times due to assisted GPS
This made me laugh and reminds me of walking my dogs. I've always said they walk twice as much as I do with their left and right in front of me to make sure they sniff every available lamp post, tree, corner, etc. I should put a gps tracker on myself and the dogs and test my theory. : )
Very interesting post, Clubberlang. I do think about this. Parkrun always comes out as more than 5K on RunKeeper and I think it’s because of dodging around people/puddles/broken bits of path. The GPS irregularities ought to cancel each other out (a metre here, a metre there) and surely are as likely to reduce the logged distance as to extend it. So yes, if timings make a difference always run the straightest line you can and take the most inside corners on bends.
Thanks.. It was one of those dinner table moments eating chicken where i thought.. Eh? these world records are down to a second.. and one guy could have run farther. Just thought it was worth talking about.
Even if you run as much to the left as to the right surely your gps logs it all as distance covered ? (most of my running is indoors as you know, so this is a genuine question)
The reason this 'argument' started with my father.. was because I have a VERY expensive watch.. that mountain climbers take up Everest, Astronauts use to go to wherever they go these days, deep sea divers.. you get the point. It's a ridiculous watch that has no place on my wrist.
But I meant that it wasn't out, even if you run to the left and the right to get around people, puddles, or just tzke the outside of a curve or get water from a drink station, your net deviation may be 0 but in metres covzred I'm sure you added a lot on. There's a reason for the staggered start in athletics
On a straight line it will average out as the GPS is as likely to be off to one side as to the other. But on corners the GPS can cheat you of metres by drawing a tighter curve than you actually ran.
Depends what you want to take as your PB. I always go by official times over Strava. For example my 5k Strava time is faster than my parkrun time but my parkrun is 5.1k actually. Some people go by Strava.
Honestly Tash, I really don't care. It just made me think about these guys who win by one hundredth of a second! 😲... They must know, like Stephen_UK says.. the ultimate route?
I can see the drop-down names, but as soon as I enter the name all sorts of chaos begins. I get an error message OR a security message OR the post vanishes OR it sort of “posts itself”! This is on an iPhone, by the way. Not hugely important, but it would be nice to be able to do it. Again, sorry Clubberlang. Your brilliant thread has been turned into an IT troubleshooting page.
No worries, Hidden has linked us in to try and help. The security message is standard you have to click to ok that, I will send a message to support tomorrow to see if any other reports have been put in. Rfc x
Well, a 400m track is only 400m on the inside lane. Obviously the athletes running shorter distances use the curving line to make sure they run an equal distance, but if you are running on the track in lane 8 from the start/finish line it is 453.66m each lap 😉
😲 My face! Right Now! Working out the obvious.. But I'm not going to be too hard on my inadequate brain.. because my point was... Over the course of a race, especially long distance, how much farther are these guys really going? I'd like to know.
Well, I guess the elite athletes are taking a pretty direct line so are very close to the marked distance. For the rest of us, I’d trust the watch!
I find the 800m race/middle distance interesting - you have runners trapped on the inside lane, stumbling over heels, then having to come out into lane 2 or even 3 to overtake other athletes. But I guess the adrenalin and maybe even some drafting?! counter that...
This was my fault on my first try of 3000 meters on a 400 m track. I wanted to be nice and was running on lane 3 because I didn't want to be an obstacle for the fast runners ... I was counting the laps ... then my watch said to my "finished!" ... but the finish line was not there! Haha, I had to run some more meters ... ;/ Stupid! But I learned that I run on the inside lane since then when it's counting for a medal!
1) I see people cutting corners on events and I often wonder why would you want to do this, you are only cheating yourself. but then they don’t seem to complain that the course is short so maybe a bit of wiggle room is built in.
2) I always start my Garmin before I cross the start line now as I have been caught out twice with a short course and my brain has to of done and finished the distance. I once did a fun run and carried on after the event so I could claim a 5km Pb, I did look weird as I just kept on running as I past the finish line, think a bit Forest gump style, MrRfc was totally bemused. 😂😂😂.
Interesting post clubberlang. I always run with my phone using Runkeeper and my ancient Garmin Forerunner 10. The distance ran on each are never the same, especially when I'm running the trails without cell coverage. I've always ran my prescribed distance using Runkeeper to be consistent although I think the watches are much more accurate (and my pace is always faster, since the distance is consistently longer on my watch). But lately, with my trail HM training, I'm running based on my Garmin, which means some of my training runs aren't being marked as complete on my RK plan. No big deal...so I try to tell myself 🙄. I know the runs I've done. I think the biggest comparison for you, will be when you run this race again next year, can you beat it? And will you run 10.4 km again😁?
Sorry Sask, I was answering a lot of people and I didn't respond to you... EASILY one my of best VRBs.
Yeah, your runs are really what i'm talking about, these ultra marathons through deserts, over mountains.. they say it's a certain distance, but who knows what you're actually running? 😳 It's more orienteering than a race.
I don't trust the accuracy of GPS for distance anymore than I would trust a dog to guard a pile of sausages. There are way too many ways for the signals to bounce around off trees, buildings and even bodies of water (lakes, canals) which confuses the device and results in an imperfect route trace.
Next time you use it for a race look at the trace carefully and ask yourself the questions Did I really run "through that hedgerow"/"on the other side of the road"/"run across the canal"/"through that postbox"
GPS is notorious for cutting off corners reducing the distance traveled but it can go the other way too and add distance, for example if it thinks you took much wider lines through corners or by zigzagging the route slightly.
Satnav devices have an advantage here in that they know you're going to follow the road rather than drive in to the hedgerow, so can adjust and interpret the imperfections in the GPS triangulation more effectively. Next time you decide to ignore the instruction to take an exit off the motorway and go a different route keep one eye on where your satnav thinks you are and how long it takes to accept that you didn't go where it told you to.
I should add, I'm in no way saying GPS is useless, totally the contrary, but I see it as about an accurate a guide as I can have of how far I ran. If I run a UK athletics licensed 10km race, then it means the course has been measured accurately around the racing line. It's definitely still possible to run longer or shorter distances, but unless you have a military grade GPS device (which use encrypted signals from the satellites and aren't available to consumer grade devices) I doubt you'll be able to determine that based on what your watch recorded.
I just had a look at the route MapMyRun shows for my last parkrun and it has me running all over the place, including through the lake and out of the park! So that explains why it thinks I ran 5.2km.
I had heard that civilian gps is deliberately inaccurate, to give the military the edge against terrorist organisations etc., It would make sense, although I don’t know if it’s really true.
It's true that the US authorities used to have ability to intentionally degrade GPS signal quality (Selective Availability) but they claim to have turned that off years ago and that they have no intention of doing it in future. The Galileo wikipedia page can be quite an interesting read en.wikipedia.org/wiki/Galil...
Interesting discussion point. Can I throw in another? If I am running up a hill (in my dreams!🤣) is the distance shown on my running app the actual distance (ie the hypotenuse) or the crow flies distance?
I would say it measures actual distance. If you're running a mile up a hill, you're running a mile. Strava takes all this into account with GAP... Grade Adjusted Pace. So you'll get your actual running time and your GAP time. GAP estimates what your run time would be if you were running on a flat path. So If you're running a hilly course, your GAP time will be faster than your actual time. It's worth a look.
Really good point. I think it's the latter (crow flies distance). I don't think the GPS knows and accounts for exactly how high the hill or gradient is, so it's distance calculation will be inaccurate.
Not trying to get all math here, but if it was an isosceles right triangle, then the hypotenuse is about 41% longer than the side. So if the slope is around 45 degrees and you're running up that hypotenuse then you're covering 41% more distance than if it was a flat path. Lesser the slope, lesser will be that extra distance covered.
Now imagine after you ran up that hypotenuse, the hill drops down to the same level as before. This means that you have run 2 hypotenuse's (holy cow!). Assuming the slope is the same of about 45 degrees, then you've just ran about 82% more than if it was a flat path.
Now if you ran around the hill, then you're effectively running on the half-circumference....nah! I won't bother with the math (psst, it's 107% more...so more than double than if you just ran through the hill). So going over the hill is 82% and going around it is 107%...hmmm, which do I choose
GPS can accommodate elevation, so if you run a mile up a hill then you should be tracking a mile (within the usual +/- error rate) with GPS as well. It's not perfect, which is why Strava has an elevation correction feature, but that feature is turned off by default if your GPS watch has a barometric altimeter as it would normally do a better job.
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(psst, it's 107% more...so more than double than if you just ran through the hill). So going over the hill is 82% and going around it is 107%...hmmm, which do I choose 
Finally, a run!
Should I run my 10k race on Sunday?
Leggings are like satsumas 😃, peel a satsuma and you eat it! 555 seconds!
The best run yet. By far.
