Answer- it varies! Depending on your phone, the network, your location and which app you're using! (at the moment in a built up area with lots of masts and wifi around as well I'm showing about +/-20m).
I recently read a posting comparing the accuracy of Ordnance Survey Map grid references on an iPhone and a G3 (on "Gavin's Gadgets"- some great articles- and photo comparisons from lots of devices). The iPhone appeared to be way out in the article and it got me wondering because last weekend, whilst walking and comparing an HTC One, Nokia 1520 & iPhone 5s I was comparing navigation and location accuracy. I was by the coast it was pretty easy to know exactly where I was. Of the three, the Nokia 1520 and iPhone 5s gave my actual position on satellite maps most accurately. I wasn’t specifically looking at grid co-ordinates. So just now I fired up the three devices. Quickly looking at the 1520 & HTC One, the grid refs match to 8 figure accuracy. The iPhone is out noticeably (using the ViewRanger app on the iPhone and on the HTC One). Out of curiosity I downloaded ‘Coordination’ (app on iOS to give grid references). And it’s grid ref matches the HTC One and 1520. Quick conclusion- ViewRanger on iOS isn’t accurately showing my grid references- certainly compared to other iOS apps (I’ll contact the maker- though might be a setting difference between my iOS and Android version in ViewRanger). I'm in a built up area and lots of masts and wifi signals around (about +/-20m accuracy).
It got me thinking a bit more about what affects locational accuracy - and as I dug deeper I found several approaches used to determine accuracy on Smartphones- and realised there was more to this. Garmin were touting WAAS (EGNOS in Europe) with a quoted ‘5 times more accurate than GPS’- which got me thinking that if I was out walking in the wilds something like a Garmin device would be useful alongside a phone!
A couple of interesting sites I found along the way:
http://www.follow-the-arrow.co.uk/resources/gps.html
http://www.andygup.net/how-accurate-is-android-gps-part-1-understanding-location-data/
http://www.andygup.net/how-accurate-is-android-gps-part-2-consuming-real-time-locations/
UPDATE: issue with Viewranger on iOS is due to a difference in behaviour to the Android version of ViewRanger (and most map apps on iOS). Most map apps on iOS and Android (including ViewRanger on Android) default to using the grid reference system used on Ordnance Survey maps. However, ViewRanger on iOS defaults to using a different reference system. There is a settings option in ViewRanger on iOS to change the grid system to the more widely used system (at least in the Uk) and to bring it in line with the android version.
I recently read a posting comparing the accuracy of Ordnance Survey Map grid references on an iPhone and a G3 (on "Gavin's Gadgets"- some great articles- and photo comparisons from lots of devices). The iPhone appeared to be way out in the article and it got me wondering because last weekend, whilst walking and comparing an HTC One, Nokia 1520 & iPhone 5s I was comparing navigation and location accuracy. I was by the coast it was pretty easy to know exactly where I was. Of the three, the Nokia 1520 and iPhone 5s gave my actual position on satellite maps most accurately. I wasn’t specifically looking at grid co-ordinates. So just now I fired up the three devices. Quickly looking at the 1520 & HTC One, the grid refs match to 8 figure accuracy. The iPhone is out noticeably (using the ViewRanger app on the iPhone and on the HTC One). Out of curiosity I downloaded ‘Coordination’ (app on iOS to give grid references). And it’s grid ref matches the HTC One and 1520. Quick conclusion- ViewRanger on iOS isn’t accurately showing my grid references- certainly compared to other iOS apps (I’ll contact the maker- though might be a setting difference between my iOS and Android version in ViewRanger). I'm in a built up area and lots of masts and wifi signals around (about +/-20m accuracy).
It got me thinking a bit more about what affects locational accuracy - and as I dug deeper I found several approaches used to determine accuracy on Smartphones- and realised there was more to this. Garmin were touting WAAS (EGNOS in Europe) with a quoted ‘5 times more accurate than GPS’- which got me thinking that if I was out walking in the wilds something like a Garmin device would be useful alongside a phone!
A couple of interesting sites I found along the way:
http://www.follow-the-arrow.co.uk/resources/gps.html
http://www.andygup.net/how-accurate-is-android-gps-part-1-understanding-location-data/
http://www.andygup.net/how-accurate-is-android-gps-part-2-consuming-real-time-locations/
UPDATE: issue with Viewranger on iOS is due to a difference in behaviour to the Android version of ViewRanger (and most map apps on iOS). Most map apps on iOS and Android (including ViewRanger on Android) default to using the grid reference system used on Ordnance Survey maps. However, ViewRanger on iOS defaults to using a different reference system. There is a settings option in ViewRanger on iOS to change the grid system to the more widely used system (at least in the Uk) and to bring it in line with the android version.
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