Accuracy of Strava -v- Garmin

bails1310

I have until now used Strava to log and check how I'm doing.

Last week I took the plunge and purchased an Edge200 which I think is great but on last nights 18m commute home, thought I'd run them both to check if they were similar. On the whole they were, time, average & miles were very similar.

What wasn't was the accent [800ft on the Garmin, 600ft on Strava] and the biggest swing, calories [1,000 on the Garmin and 700 on Strava]

Some might argue that these are less important than speed, miles etc., but equally I don't want to assume I'm doing more climbing than I thought or burning more cals.

My profile on both is exactly the same [age, sex, weight] so interested to hear if anyone else has this and if so, which is the more reliable/accurate?

wongataa

I wouldn't really trust either of the calorie numbers as they are both just really educated guesses using different algorithms.

Are you using gps data from the Edge 200 in Strava? The edge will use GPS data for the altitude. GPS altitude isn't that accuarate so the numbers on the Garmin are are rarely likely to be accurate and will give different values every time you do the same route. Strava could be ignoring the GPS altitude data and instead use elevation data generated from NASA's mapping missions. This is what is used in Google Earth may not be accurate either due to the resolution and land cover. To know what the elevation profile should be you would have to carefully use OS map data and work it out yourself.

bails1310

I used Strava [as I did last night] on my phone and recorded the Edge on it's own.

I was planning to use the Edge to log and then upload onto Strava but as you say, may now be logging difference stats for the same route.

Suppose I'll just stick to the speed etc stats which seem to be accurate.

I did have a go at the loading of maps which I think is a great function to be included for the money.

philwint

Remember that strava just consumes the gps data from the device. Garbage in:Garbage out.

Given Garmin have long been worl leaders in GPS technology and the Edge is pretty much a dedicated GPS tool

And the smartphone you have previously collecting data is none of these things - I'd be tempted to go with the Garmin results.

But yes - if Strava have base maps they are preferring to the gps altitude data the *may* be better.

And if you have a HRM strap on for the Garmin that is going to be much more accurate an approximation of calories than raw strava.

thegreatdivide

In regards to Garmin and calories. This link was posted earlier in the week and it's really informative http://www.dcrainmaker.com/2010/11/how- ... armin.html

You say you've just got the Edge - have you calibrated it properly yet? When it comes to elevation my 800 and Strava are pretty much bang on.

binsted

I have noticed that with my Edge 705 I need to turn it on let it acquire the satellites and then leave it for another couple of minutes for the elevation data to find and correct, if I turn it on while rolling the elevation data is well adrift.

bails1310

thegreatdivide wrote:

In regards to Garmin and calories. This link was posted earlier in the week and it's really informative http://www.dcrainmaker.com/2010/11/how- ... armin.html

You say you've just got the Edge - have you calibrated it properly yet? When it comes to elevation my 800 and Strava are pretty much bang on.

Its on the 200 so when you say calibrated, what do you mean? Weight & height?

nawty

Aside from the calories and height data, I tend to believe Strava over Garmin connect (both using the data from my Edge 500).

The Garmin just reports the GPS data whereas Strava maps that to the roads which you were cycling along, given GPS isn't that accurate (which you can tell from the number of false off course alerts you get when following a route or be reviewing the route in detail) I think the Strava approach is better.

With regards to calories, I use the HRM with the Edge 500 with all of my data inputted the to get the most accurate calorie count. I do take it with a pinch of salt though and I find that on shorter rides it gives me higher readings that Strava whereas on longer rides it reads less, I guess this is to do with the heart rate factor as I tend to go easier on longer rides.

edit: I wouldn't believe anything that was just calculated from the GPS (i.e. weight x speed) as that tends to massively over-read. For example on a recent hilly 58m ride my HRM based setup calculated I burned 2200 calories (which feels about right and incidentally is what Strava reckoned too) whereas my friend, who is a similar weight burned 3700 calories according to his Garmin with no HRM which is way too many.

smithy05

I did use to think Strava was super accurate in terms of distance covered. However, yesterday I did a 24.1km ride according to Strava and today did exactly the same ride, only for it to read 23.1km. I plotted the route on Running Map which gave me a reading of 22.8km, exactly what my Polar computer also said.

smoggysteve

There are so many variables to consider between the two that you will never really get a true accurate calorie count or elevation. As for calories, your age, height, sex, metabolic rate, weight all are factors in how you burn calories.

On the side of the elevatio, there are different standards for mapping. Many countries use their own system and the difference from the mapping and the GPS will vary. I tend to set my garmin to German mapping in Germany obviously, but if I compared it to MGRS which is a more accurate military grid system but only if I use military maps. As the maps used for strava and garmin vary from whoever they license the mapping from accuracy cannot be 100% correct.

EDIT: one other thing. The UK takes all heights from mean sea level. MSL which is calculated from what aviation call QNH as a height above see level reference. This is only used by UK aviation, and is used on UK ordanance survey maps. Many countries use their own system which is also used for mapping. Therefore the program used for the mapping needs to know which. If you used google maps, they would use the satellites elevation data which will not neccessarily match the GPS data for a given grid system.