# Strava with Galaxy S2



## McGuillicuddy (Jul 14, 2007)

I'm using Strava with my Galaxy S2 (i9100). I often ride with a buddy and we both have Strava running (he uses a Blackberry). Time and time again we'll do a segment almost side-by-side the whole way yet when I get home and look up Strava it shows me taking 10 - 30s longer than my buddy. 

My only guess is that my GPS sampling frequency is too low and there may be lag between when I actually finish a segment and when the GPS records it.But that's just my guess - I don't know much about these things.

Does anybody else have this issue, especially with the SGS2? Can anything be done? My phone isn't rooted but I'll do it if it means I can get my GPS to do a better job.


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## McGuillicuddy (Jul 14, 2007)

Just one more point. Apparently GPS Logger for Android allows you to specify the GPS interval (Strava does not). I'll download that and see how well it works. Will report back.


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## Harold (Dec 23, 2003)

it could be sampling interval. it could also be differences between the accuracies of the different GPS chipsets on the different phones. It could be differences between the GPS antenna in each of the different phones.

Onboard phone GPS hardware is just not that good. The GPS apps on the phones have to do a LOT of processing or "massaging" of the raw data to give you something useful that dedicated GPS receivers don't have to do. The best way to address it would be to buy an external GPS receiver that connects to the phone via Bluetooth. These devices have better GPS hardware and bigger antennas, and because they're separate, they can be placed in a more optimal location for the best reception.

This kind of hardware has been around for years. Long before "smartphones" really came out. The old Palm Pilots and early Windows mobile PDA's used to use them because there was no such thing as integrated GPS chipsets. Onboard GPS in a smartphone is fine for general navigation purposes, but if you're serious about quality data, they're not good enough. And if you're quibbling about 10-30sec of time on a GPS track, that tells me that you have graduated to being serious about quality data. Your other alternative would be to buy a dedicated GPS.


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## car_nut (Apr 5, 2010)

Go on Strava and click the segment time for each of you, comparing the start/stop points. In my experience, Strava calculates an average error for your data set and then gives you the benefit of the doubt. Meaning, if your data set is really clean, they'll start the clock when you're within 20ft of the start. If your data is crap, they'll assume you started the segment when your data is 100ft past the start. Also, if the loop includes any sort of switchbacks near the start/stop, Strava applies the same logic. Meaning it could start the loop in the correct spot if your data is clean. If the data is noisy, it'll call the start when you've completed the first switchback and are coming back towards the start/stop point.

Overall I've found Strava to be pretty useless for timing any sort of trails that don't have a long straight at the start/stop(not Strava's fault, the data is what it is). Loops are also a mess since it can't tell which way you're running the loop.


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## McGuillicuddy (Jul 14, 2007)

Ugh. GPS Logger was worse. Sampling rate was very low even though I told it to log every 1s.


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## McGuillicuddy (Jul 14, 2007)

Hmm...it appears this might be the problem:

Samsung Galaxy S2 GPS Problem? SOLVED! « Galaxy S2 « Geotools « Its Not About The Numbers

Now I just have to figure out how to root my phone...


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## car_nut (Apr 5, 2010)

McGuillicuddy said:


> My only guess is that my GPS sampling frequency is too low and there may be lag between when I actually finish a segment and when the GPS records it.But that's just my guess - I don't know much about these things.


Did you compare and interrogate your trace vs. your friends like I suggested? If you're not sure what to look for, post the strava link for you and your friend on the same segment I'll check it out.


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## StravaTR (Aug 17, 2012)

*Strava support*

Hey McGuillicuddy,

Travis here from Strava support. Strava app GPS sampling is 3 seconds so you shouldn't see differences in segment timing greater than 6 seconds max. If you're seeing larger data gaps or differences in segment times then it's likely your phone is collecting poor quality GPS points and they're being tossed by the app during data processing. We'd have to look at specific activities and segment efforts to see exactly what's happening but we do have ways to improve data quality in some cases.

I'd encourage you to submit a support ticket. We respond within 2 business days and we'd love to help.

Cheers,
Travis
Strava Support Team


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## veronicazora (Sep 22, 2012)

I've logged 2,600 miles since I commenced using it, and aside from the rogue gradient issue. I have observed that segments created with iPhones rather than GPS devices tend to be less accurate, there are a several in my area where the segment 'wanders' off the road.


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