Strava

Yes, GPS is a signal broadcast from satellites open to all (although there is an encrypted channel which is US military only, giving enhanced accuracy). Your phone has a dedicated antenna for this as well as the mobile network one, the WiFi one and the Bluetooth one. Your data bill is for data transfer over the mobile network only. You can listen to the GPS satellites' broadcasts for as long as your battery lets you and you won't be charged a penny.
If your data connection is enabled and you aren't connected to a WiFi network then your phone will talk to your provider's aGPS servers (see wiki link above) to let you ascertain a fix more quickly. Also see the stuff about Google's WiFi hotspot location database above.

I had a tough friday and 1/2 of saturday
http://www.strava.com/activities/190934532

wow! kudos given, looks like a fun ride :-)

Apparently, if you zoom in far enough in data view, you'd see little bumps deviating from the actual pace:

http://www.scarletfire.co.uk/how-to-tell-if-someone-used-digital-epo-to-cheat-on-strava/

There are plenty of other ways of doctoring GPS tracklogs so that they don't exhibit this behaviour. Removing points and shuffling up timestamps (which is what digital epo did) is a very naive/basic method.

A while back I wrote some tools to analyse tracklogs to pick out the obvious ways of speeding up tracklogs (point removal/shuffling, interpolation, etc). This can be made much easier if there's extra data such as HR, cadence or power as it is much harder (but not impossible) to fake the speed increase along with realistic corresponding changes in HR/cadence/etc.

For example, if cadence data is present then can even be possible to have a reasonable guess at the gearing setup of the bike if you plot cadence against computed speed and look at the resulting bands that the points will fall into (albeit quite noisily).

I'm sure Strava can do this given their huge corpus of data. It'd be nice if they did this at some point in the future and retrospective flagged all of the dodgy looking uploads.

I'd love to see a GPS device that cryptographically signed each trackpoint (just the time and position data is enough) so that they could not be messed with, but there's no chance of this.

Did hill repeats yesterday in thinly veiled attempt at KOM. Failed. 6 repeats much nausea
http://www.strava.com/activities/192285292

that gradient is insane..

I can get two whole days of strava out of my phone with the data off, still had 28% left on the second evening, which 4 hours of WiFi then finished off. Sony z2 are powered by magic, also properly waterproof, tested this by leaving it in the bottom of a lake in Croatia...

what's the battery life on a garmin then?

12-14hrs on an edge 800 with screen on lowest brightness, not navigating and minimal screen backlight activation.

far superior than my nexus smart phone then!

They should make an Edge800/1000 with an E-ink display...

I got about 10hrs on South Downs Double before recharging, was on OS maps view most of the time, which is heavy, didn't use backlight even in the dark as I had Exposure Diablo on my helmet.

On a road ride down to Falmouth from here (Devon), It lasted the duration >13.5 hours I think including stops which I didn't turn it off. I just checked the maps occasionally and used Open Street Maps not OS maps, which are much less memory (therefore battery) hungry.

Read the previous page? Or the Garmim thread?

there's a garmin thread??? linky plz

http://www.lfgss.com/conversations/185085/newest/

http://www.lfgss.com/search/?q=garmin&defaults=true

Have two ;-)

much love

Snoopy Kissed Marcy also giving me Kudos on my boring commute. What's that all about then?

Went cycling in Switzerland over the weekend. Strava said I climbed 7,460 feet on Sunday, while someone else on the same ride recorded 5,730.

@pharoahsanders

Unless you tell Strava to recalculate the elevation it normally uses what it got from the device. Even the same GPSes on the same ride can be way out from each other as they slowly get better/worse lock (positional accuracy is favoured over elevation accuracy).

Even when you tell Strava to recalculate it'll be based on an imperfect set of DEM (Digital-Elevation-Model) data.

Just ride the bike and ignore that kind of stuff.

I don't care too much about the data, I just found it interesting in the context of the discussion upthread about strava accuracy.

I blocked that account last week.

wheelsucking behind a Hayabusa when curryring paid off this morning I see... ;-)

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