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I'm using a midrange Android smart phone to collect gpx tracks for adding trails, and checking road alignment. I am often surprised to see how much the gpx track wanders when I'm cycling down a straight road. The phone reports it's accurate to with in 5m, but I think it's more like 10m or more off. Would I see a big improvement if I switched to a dedicated GPS? As most of the mapping I do is done while cycling I was looking at the cycling specific GPS units, that come with handlebar mounts, and other bicycle related features. The Bryton Rider 530 looks nice, but I'd be interested in hearing suggestions. |
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One factor that can affect all GPS receivers is device orientation. For example if the device is in a pocket or backpack, the orientation can change while moving and affect accuracy. Handlebar or stable mounts should provide an improvement for any device. Tall buildings on either side and leafy trees overhead can also affect any GPS device. A dedicated GPS should be slightly more consistent but I've not seen large differences under ideal conditions. |
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I guess it depends on your phone and your GPS device. In my case I find my older Garmin eTrex 10 does a better job than either my current mid-range Android phone or my previous high end Android phone. While my current phone claims to use the Russian Glonass satellites in addition to American GPS satellites I've never seen it do so. The old Garmin actually does use both systems, locks faster and returns much more consistent positions and tracks. When hiking, the phone's GPX track will wander all over the place. On the eTrex, my return track will be within a couple of meters of my outgoing track. In addition, the eTrex has a waypoint averaging feature where I can get a point position very accurately especially if I have it average the same place several hours apart (or better on different days). I use that for making sure trail junctions are accurate, etc. On the other hand, collecting any data where you need to type is a real pain on the eTrex. If I am collecting house numbers it is much easier to use Keypadmapper on my phone (I have built my own version that doesn't automatically report to OCID) or if I am surveying businesses I use OsmTracker with its default button set to either voice record data or take photos. For collecting speed limits I use OsmTracker with a custom button set that makes it easier for me to use in the car. When using data collected via Keypadmapper or OsmTracker I know that the positions will be approximate and use Bing imagery for better positioning (after verifying the imagery location seems reasonable based on an visual average of uploaded GPX tracks and/or the GPX track from my eTrex). Regardless of using a phone or dedicated GPS device, there are times and places where GPS is going to inaccurate. Deep canyons (or the urban equivalent) restrict the view of the sky and you will consistently have bad positioning. Wet tree leaves block the signals, so in a forest in or shortly after rain will be bad. And there are other things that can make a difference. |
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See the "GPS Accuracy" picture on this page: https://www.singletracks.com/blog/mtb-gear/gps-accuracy-gps-vs-smartphone-vs-cyclocomputer/. There it is evident, that for example the "iPhone 6s" has much higher variance than the "Garmin Edge 520" or the "Bryton Rider 330". Also here is a nice comparison: https://www.singletracks.com/blog/gps/gps-distance-accuracy-test-smartphone-apps-vs-dedicated-gps/. So standalone GPS can be a major improvement in terms of positioning variance. (Or the iPhone is bad. :D) Furthermore, I'd suggest to mount the GPS device on your helmet for lowest positioning error. I found, that by carrying a smartphone in an arm-band on my right upper-arm facing outwards resulted in a systematic(!) positioning error of 5m to the right. I was running in a forest. So deflection and reflection of GPS signals is essential. |
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I'm using a Garmin 62s, which usually is mounted on my handlebar. For an idea of the accuracy with this setup, see the traces in/around https://www.openstreetmap.org/relation/2845739 (the vast majority of these are mine). |
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I sometimes record my walks with two devices, Garmin Oregon 450 and Moto G3 android phone. The Garmin can be set to record points more often but otherwise the traces are very similar. Maybe you would like to compare two pairs of traces with possibly JOSM or GPS Prune. The two pairs I recorded on 02july2017 and 04july2017 are here https://www.openstreetmap.org/user/andy%20mackey/traces note the garmin is in a pouch on backpack chest strap and the motorola is in a clear neck pouch so both can get a good signal, as suggested in one of the other answers. |
