Garmin Edge 200 vs Polar M460 ....what gives ??

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cyclotaur
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Garmin Edge 200 vs Polar M460 ....what gives ??

Postby cyclotaur » Thu Sep 13, 2018 3:29 pm

I've had the Garmin since late 2011 and used it exclusively until getting the Polar (with HRM) last Xmas. Since then I've mostly used the Polar but since I got a 'new' road bike last week I put the Garmin mount back on the gravel bike and the Polar mount on the road bike.

I'd done a few comparison rides early this year and noted a few discrepancies but nothing major - different elevations mostly - but time and distance data was close enough. I think the biggest difference was maybe 1 km in about 75 for distance with Polar reading slightly shorter. Today I did a ride on the gravel bike with the Garmin and for fun I carried the Polar in my jersey pocket.

Moving Time:
Garmin read 2:33:18......Polar read 2:33:20 - pretty close.
Elevation:
Garmin read 418m ……..Polar read 435m - also close.
Distance:
Garmin read 51.01 kms….Polar read only 48.48 kms...... Huh??

Anyone struck such a large distance discrepancy between devices? I mean that's 5% in 50kms.

I've noted big elevation differences between bike computers and the iPhone Strava app but the time and distances always matched up. This difference seems pretty significant to me.
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rodneycc
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Re: Garmin Edge 200 vs Polar M460 ....what gives ??

Postby rodneycc » Thu Sep 13, 2018 4:11 pm

One isn't using Glonass instead of GPS is it? But yeah sounds dodgy. What did the GPS on your Phone say. Would be a good comparison as well.
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cyclotaur
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Re: Garmin Edge 200 vs Polar M460 ....what gives ??

Postby cyclotaur » Thu Sep 13, 2018 4:23 pm

Glonass ? :?
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rodneycc
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Re: Garmin Edge 200 vs Polar M460 ....what gives ??

Postby rodneycc » Thu Sep 13, 2018 10:07 pm

Yeah its like the Russian satalites. Garmins can use both or either. Maybe just Google it. :-)
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cyclotaur
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Re: Garmin Edge 200 vs Polar M460 ....what gives ??

Postby cyclotaur » Fri Sep 14, 2018 2:33 pm

rodneycc wrote:Yeah its like the Russian satalites. Garmins can use both or either. Maybe just Google it. :-)

Yep, thanks, did exactly that. It seems Garmin uses both by default, Polar only uses GPS.

Anyway, did the same again today and the results for distance were within 180m over 39kms, so much better. Todays ride was basically east up the Koonung Trail, whereas yesterday was north up Darebin and back down Plenty Trail.

Perhaps those Russian satellites have better coverage over the Peoples Republic of North Yarra !! :D :D
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BJL
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Re: Garmin Edge 200 vs Polar M460 ....what gives ??

Postby BJL » Thu Sep 20, 2018 11:36 am

cyclotaur wrote:
Moving Time:
Garmin read 2:33:18......Polar read 2:33:20 - pretty close.
Elevation:
Garmin read 418m ……..Polar read 435m - also close.
Distance:
Garmin read 51.01 kms….Polar read only 48.48 kms...... Huh??

Anyone struck such a large distance discrepancy between devices? I mean that's 5% in 50kms.

I've noted big elevation differences between bike computers and the iPhone Strava app but the time and distances always matched up. This difference seems pretty significant to me.


The difference in elevation between the bike computers isn't that close. 17 metres over 418m is still about 4% difference. My last job involved calibration of various transducers and we always aimed for 1% or less error when compared to a reference. If both bike computers are using barometric air pressure sensors for elevation, 1% for me is the maximum acceptable difference. Having one in your pocket and one mounted on the bike might have made that difference though.

I walked 20kms last Sunday. Started and ended at exactly the same location. Used a Garmin Edge 500 to track the walk. Over 4+ hours where changing weather conditions can have an effect on barometric air pressure sensors. Over those 4+ hours, the difference between ascents and descents was only 3-4 metres, with around 640 or so metres climbed/descended.

Ever seen someone's activity where the the elevation suddenly shifts a couple of hundred metres? It's a dead giveaway they stopped for a period of time for lunch or whatever.

Quick tip - I find that using 'elevation points', where you manually set the elevation at a particular location (I know my driveway is 217 metres above sea level and that's where I start/end most of my rides/walks), greatly increases the accuracy of elevation readings. Before I did this, some of my rides were starting 50-100m below sea level!

It's funny. I did a ride about a year ago with a mate of mine. Exactly the same ride except he had a 'better' Garmin, well according to him anyway. An 800 series compared to my 500. His elevation was different to mine. Now, the entire route was almost flat except for one hill. My GPS recording the same maximum height for that hill on both passes (it was a 'there and back' ride). His recorded a different elevation for both directions. About 40 metres out from memory. Somehow, I don't think that hill changed height over the course of the day. So whose GPS data would you consider more reliable? Mine were the hill stayed the same height or my friend's whose GPS decided the hill had grown? Of course, since my friend had recorded more elevation for the day for exactly, and I mean exactly the same ride, he claims his device was more accurate. But when a hill grows 40 metres in a day (and no, it's not a volcano), then yeah, okay then.

As for distance, are you using a wheel sensor for one or both of the bike computers? Or relying on GPS? This can make a difference as different GPS receivers (even of the same make and model) can vary wildly.

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cyclotaur
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Re: Garmin Edge 200 vs Polar M460 ....what gives ??

Postby cyclotaur » Thu Sep 20, 2018 2:22 pm

I'm not so concerned with the elevation differences, though I do a lot of climbing rides.
It's mostly the large difference in distance between the two devices that bugs me.

Yes its all GPS derived. I had an old school wheel sensor computer years ago pre-Garmin. When I got the Garmin they matched really well for distance, so I actually now trust the Garmin distance over the Polar.
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Tim
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Re: Garmin Edge 200 vs Polar M460 ....what gives ??

Postby Tim » Thu Sep 20, 2018 2:44 pm

BJL wrote:Ever seen someone's activity where the the elevation suddenly shifts a couple of hundred metres? It's a dead giveaway they stopped for a period of time for lunch or whatever.


Or the weather changed suddenly.
I once rode into a summer thunderstom. The Garmin elevation profile showed an immediate and dramatic climb in elevation.
I gained something like 500 metres of altitude in about 2 minutes (from vague memory).

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