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PostPosted: Wed Oct 30, 2013 7:04 pm 
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I don't remember, it was a few weeks ago and not my unit, I can ask next time I see the person who used it. I all get any pertinent info when I see him.

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PostPosted: Wed Oct 30, 2013 7:10 pm 
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For those that use Strava or the like, the only real option is a GPS device (whether bike computer or smartphone). Plenty of evidence out there that smartphone strava app is very inaccurate based on data sampling rate (call it digital doping) and that a Garmin type device is much more accurate.

http://www.wheelsuckers.co.uk/profiles/blogs/got-a-strava-kom-which-one-garmin-or-iphone

http://www.scarletfire.co.uk/2013/03/strava-will-you-record-faster-segment-times-with-the-android-app/


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Posted: Wed Oct 30, 2013 7:10 pm 
  • Garmin Edge 810
  • 579.00 €   from 349.90 € (including 19% VAT)
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PostPosted: Wed Oct 30, 2013 7:13 pm 
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Also don't forget your complaints were in reference to a MTB'er on a single track. That is going to be an issue with just about every GPS (that I know of). However, something with GPS + GLONASS will do significantly better as it has more satellites to use for positioning. Also increasing the data sampling rate will help. But since this is a road sub-forum, those issues that MTB'ers deal with are not something that we have to deal with for the most part.


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PostPosted: Wed Oct 30, 2013 7:34 pm 
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Location: Alberta, Canada
I thought I might wade into this a bit, not because I have any particular opinion of GPS cyclocomputers but because these issues are fairly well understood outside of the realm of cycling. I happen to be a biologist who uses GPS technology to remotely upload location of large mammals in forest (not anywhere near the ideal situation I, and others typically face on a bicycle).

What you must recall is the the jittering of locations observed on replicated tracks is due to sampling and the inherent measurement error present in recording data. We all make these error within acceptable limits when reading off a tape measure for instance. The US military used to add extra error, what was called selective availability...that all ended about a decade ago. The error that remains does exist and regardless of how minor it is must be accounted for. Depending on your needs this measurement error may be unacceptable (as we can see from some posts here). However there is absolutely no way around it. Some units may be better then others (or even phone vs cyclocomputers) but all will suffer....it is a inherent statistical property of sampling.

I have attached a paper I worked on some time ago where we were interested in the extent of this error. It was quite simple really, set out a collar in a known location and record thousands of locations. From this we could plot the X and Y errors and describe their statistical distribution. Unfortunately this may be difficult with cyclocomputers/phones which turn off when not moving.

Plotting 4 loops of a circuit will be completely insufficient to tease out the measurement error of the computer. Once you have a 100+ tracks with locations being obtained at the SAME ground location it would be as simple as taking the average X and Y locations and you would arrive as close to truth as possible. This is because the distributions are symmetric. This is the same reason that while being 14 feet off each location could theoretically put you in a different state within hours the errors do tend to even them selves out making the summarized ride statistics completely correct. The feeling of the data betting off is made worse by the fact that on the different laps the locations are probably not taken at the exact same true location and the computer connects the two data points with a straight line making the segments look different.

So if your ride data has issues or wonky segments remember that drawing from these distribution thousands of times over the course of a long ride will inevitably lead to a statistical outlier...its a statistical inevitability of sampling data

There are further papers in the wildlife literature that follow up on these effects and the influence they have....most are not that relatable here, save this, the questions you ask of the data can not be finer grained then the accuracy of your data.

Obviously this does "fix" the problems people may feel their units have but hopefully it may throw some light on the issues.

Sorry for the long winded post!!

http://www.ualberta.ca/%7Evisscher/LINK ... er2005.pdf" onclick="window.open(this.href);return false;


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PostPosted: Wed Oct 30, 2013 7:44 pm 
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Location: Alberta, Canada
I forgot to attach the paper were the distribution of GPS measurement was estimated...if your interested in it's shape!!


http://www.math.ualberta.ca/~mlewis/Pub ... rst---.pdf


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PostPosted: Wed Oct 30, 2013 8:34 pm 
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I'll read your linked articles first, but my 6 year old non-glonass GPS device took some plenty fine unobscured data this morning. And yesterday morning. And every ride before that. Seriously, I don't get why you're trying to convince people that something that obviously works, is garbage.-


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PostPosted: Wed Oct 30, 2013 8:46 pm 
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Location: Alberta, Canada
Kulivontot, i don't think they are garbage...they are the best thing since sliced bread....a technological marvel. I don't understand complaining about something that statistically speaking must have some error since it is a sample! I think you have got me wrong, I would buy a garmin in a moment, I just won't complain when the odd point is peculiar! The bloody signals go to space and back....how cool is that. My long post was in response to people who say, "it's off and is rubbish", when you can't compare a small number of samples to some unknown truth.

Sorry if I was misinterpreted.

Clearly this is my unscientific response to this thread. I actually came to this thread to see people's opinion of the 510 vs 810 to help me decide which one to get.


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PostPosted: Wed Oct 30, 2013 9:59 pm 
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Excuse me, and I apologize if this is a redundant post because I haven't read everything since I thought about asking it... but for those that are complaining that when they download the data the points are all over the place, I would ask what they have their settings at. For example, if you only have it on "Smart Recording", that will produce points all over the place. You should have it set to Record Every Second. On roads, I've always found it tracks right on, and once overalayed onto mapping software, I can even tell which side of the road I'm on. I crashed once at 25mph, and went over the road barrier into the ditch. It showed the line along the road than an abrupt change of direction for 5' off the road, then FULL STOP. I was out for the rest of the season, but I remember posting all the stats of exactly how fast I was going, what power I was putting out, the cadence and heart rate, just for fun and to bring some humor to everyone I was riding with later in the day.

I also use the speed cadence sensor because this will over ride GPS for speed etc., and even though you might lose a GPS signal if you're in the woods or covered areas, at least you still have your speed etc.

I've cursed Garmin for their lack of good manuals and the fact that it really is almost a trial and error process to really learn how the thing works in the real world, especially if you want to use it guide you from a route you've created and downloaded to the unit. But as far as I can tell, it's the best thing for the bike available right now.

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PostPosted: Wed Oct 30, 2013 10:36 pm 
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Visccher, I was responding to gitsome, I hadn't actually read your post when I had replied. Next time I'll quote. I appreciate that you're bringing some actual technical details to the discussion rather than "This one time, my friend used a garmin, and it totally sucked on like one ride. So you suck if you buy one."


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PostPosted: Wed Oct 30, 2013 11:03 pm 
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kojtl1000 wrote:
All the positive reactions here on the Garmin devices led me to decide to go for the Garmin Edge 810.
I found this 810 on ebay: http://www.ebay.com/itm/Garmin-Edge-810 ... 23312c28af" onclick="window.open(this.href);return false;

It's about $45 less expensive than the cheapest price on Amazon. Would you guys go for this? Cannot find anything on the internet on the seller (except for the reviews in ebay). The warranty is the same whatever seller you buy it from, right?


Wow, lot's of information :wink:
and sorry to quote my own post, but it seemed to have gotten lost in translation... Anyone recommend buying this through the Ebay shop, or go for the Amazon + $45 option?

Thanks guys!


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PostPosted: Wed Oct 30, 2013 11:46 pm 
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Buying from amazon or any authorized dealer means you won't have any issues with a short term return or a warranty issue down the line. Buying from eBay you don't know if the seller will take care of you in case of an issue, and whether garmin will warranty it if there's an issue later on (I hear garmin is quite generous with their warranty, but it should still be considered)


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PostPosted: Thu Oct 31, 2013 12:09 am 
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Location: nyc
kulivontot wrote:
Visccher, I was responding to gitsome, I hadn't actually read your post when I had replied. Next time I'll quote. I appreciate that you're bringing some actual technical details to the discussion rather than "This one time, my friend used a garmin, and it totally sucked on like one ride. So you suck if you buy one."



When did I say or imply "you suck if you buy one"???

Kulikov you are a touchy guy, have a beer. Thats never been my message but I guess you weren't reading my posts "objectively"

I said the accuracy sucks and thus not worth the/my money.

No need to take that personally. You need to relax.

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PostPosted: Thu Oct 31, 2013 12:11 am 
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I bought mine from ebay, though a different seller, and had no issues with getting support from Garmin. They didn't ask where it was purchased.


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PostPosted: Thu Oct 31, 2013 12:13 am 
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Seems like some people around here are way too touchy to even have a rational debate or conversation. That explains a lot.

From now on lets all just agree with everything everyone says no matter what and make each other feel good no matter what.

I gave an opinion based on observation and experience of a user just as everyone else does about everything discussed on this forum, and Garmin advertises itself as useful for mapping and Mtb so that's what I am referring to and this thread was about Garmin and GPS not Mtb, my statements on the inaccuracy and thus relative uselessness of an expensive, dedicated piece of hardware such as 510-810 hold true regardless of terrain or forum. This was a discussion about Garmin and GPS.

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Posted: Thu Oct 31, 2013 12:13 am 
  • Garmin Edge 810
  • 579.00 €   from 349.90 € (including 19% VAT)
  • in stock


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PostPosted: Thu Oct 31, 2013 12:20 am 
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I guess airplanes installing GPS avionics or water vessels using GPS chartplotters don't know what they are doing because gitsome says GPS sucks.


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