garmin says one thing; mapmyrun says another; who to believe???

[scedastic]

garmin: 18 miles, slooooow pace
mapmyrun: 19.5 miles, somewhat slow
mapping on the internet shows a little over 19 miles for the route that I ran, but using mapmyrun software.
google maps was being cranky with me, and i did a circuitous, winding route, so is there another program that is as easy with this as mapmyrun for free, just to check?

it was my first time using my garmin 410; i heard there was a way to check the signal strength/accuracy? because I suspect it shorted me early in the run, on the hills, or i was just that slow.

who should i believe, garmin or my lyin eyes??

 

[Barefoot Dama]

I would trust the garmin unless you went under a tunnel that block reception otherwise 18 miles it is the newer garmins as yours are more accurate the the older versions.
When I first started to map my runs I will drive the route the first time and after that I'll used the garming and both get me the same distance.
No comment on the lying eyes.

 

[Zetti]

.
No comment on the lying eyes.

....but Dama...there ain't no way to hide those lyin' eyes

 

[Barefoot Dama]

....but Dama...there ain't no way to hide those lyin' eyes

sunglasses? goggles? maybe a face mask? just sayin'

 

[Zetti]

sunglasses? goggles? maybe a face mask? just sayin'

NO Dama.....my, my, my, my momma said....no wait, that was the Eagles
Either way its fact!
I think...

 

[Barefoot Dama]

The Eagles, I forgot about the Eagles--you win!

 

[Hawkbilly]

I'd trust the Garmin more than Mapmyrun. Some routes I map in Mapmyrun are pretty close to actual.....but some are off by a several tenths. I've never had one as off as 1.5 miles though. The newer Garmin's.....when calibrated....should be within a couple of feet over that distance. However, if they can only get 2 satellites instead of 3 or more, the elevation mapping can be off.......which can lead to inaccuracy.

 

[NickW]

Typically I'd trust a Garmin over Mapmyrun, but the 410's for some reason seem to almost always be different than any other device I've ever used. Not sure if they are just super accurate or if they are just off a little bit.

 

[scedastic]

I'd trust the Garmin more than Mapmyrun. Some routes I map in Mapmyrun are pretty close to actual.....but some are off by a several tenths. I've never had one as off as 1.5 miles though. The newer Garmin's.....when calibrated....should be within a couple of feet over that distance. However, if they can only get 2 satellites instead of 3 or more, the elevation mapping can be off.......which can lead to inaccuracy.

See, that's what I"m thinking. At the start of my run, there were a lot of steep hills, many of which I'm used to, so it wasn't as though I was overwhelmed by them. Yet, it was taking FOREVER for mile two to ding (mile one dinged at about the 'right' point from previous runs), and it showed my speed as being ridiculously slow. This happened off and on up to about mile 6 (where it would show my pace as super slow, even after I hauled it just to see). Then, it seemed to count the appropriate miles, at least by feel, for a while. Then, at the loop point, where there are many hills, it was taking forever to knock out a tenth of a mile. Yes, at that part of the run, I was slow, but, well, it just didn't feel right.

It doesn't truly matter, I guess, since I'm not that weird about how many miles i do on a particular run, but it was such a large discrepancy that i wondered.....

 

[Zetti]

I've heard of runkeeper and Iphones really messing up, but it doesn't seem super common for this to happen with a Garmin.
However, I would say that mapmyrun can be a touch off (.1 miles or so).
but a large dependency sounds like your Garmin has gone haywire

 

[skedaddle]

If you're training by numbers then stick with the Garmin that way you have a constant to start from, as long as nothing changes on their end you will be able to measure and compare your progress with a degree of accuracy. I got a 410 for my birthday, i don't really use it to check my progress but use it more to plot my position when i'm out in the middle of nowhere. From what i've experienced it's fairly accurate.
So just choose a site and stick with it, it's the constant that is more important than the numbers.

 

[Bare Lee]

Since buying it in June, I've been pretty happy with my Garmin 210. The distances are a little less than Google Maps. The elevation isn't that accurate though, as I get slightly different readings on each repeat of my hill repeats, but I don't pay any attention to elevation since nothing here in the Twin Cities is too topographically dramatic.

 

[scedastic]

Hmmmmm............
Well, I'm going to either bike or drive the same route, just to see how consistent it would be over the course of the hills.

 

[BarefootJL]

Scedastic, RunningAHEAD (a free online running log) has a route measuring tool based on Google Maps that I think would be fairly easy to use for your purpose, you should check it out.

Now, on the GPS accuracy side... All GPS devices (watches, smartphones, navigators) use the same basic technology and just differ on the antenna sensitivity and the amount of data points they take by time interval. Even though the algorithm used to calculate the actual route from those data points may be different among devices, they all use some sort of smoothing so I don't think the algorithm has much influence. The two biggest sources of GPS errors are missing data points (due to obstructions) and erratic measurements (due to interference). Missing data points would yield a shorter distance, as having less in-between points would generate a straighter-than-actual path; on the other side, erratic measurements usually produce longer distances as some data point end up being somewhat far away from the actual route taken, thus making the route longer. So, summing up, if you think there were many obstructions on your run (trees, tunnels, etc.), specially if your route was very curvy, I would go for the longer distance, and if you think some interference could have affected your device then the shorter distance is probably more accurate.

In any case, mapping your route as close as possible using a satellite-imaging tool would always beat any device, as you're able to visually approximate the real route better.

Hope this helps, cheers!