My friend and I were making an ‘exploratory OSM trip’ not so long ago and were recording some GPS traces to upload them to OSM later on. We both had iPhones, one of which was using 3G and another one was offline.
The results we’ve got on a device that was online shocked me a little bit, so I decided to share my discovery here in the blog. Check it out:
As you see on the right image, the track is perfectly aligned to the roads on Apple maps, so there is absolutely no usefulness in uploading it to OSM (of course, unless you want to get a precise copy of a rather roughly drawn road network)!
It turns out that iPhones tend to align the geolocation to the nearest road on Apple maps when moving at certain speeds. This applies to devices having iOS6+ and either a cached build-in map or a live internet connection. Such ‘feature’ seems to be very deeply integrated into the OS, because the app we used on both iPhones was released far before Apple announced their maps. We toggled the Internet on both devices and confirmed that it was nothing to do with the model of the phone by itself.
Please beware of this problem when using your iPhone to collect GPS tracks the next time! It’s definitely worth checking them against the exact match with the Apple map before uploading to OSM or just tracing over.
Any thoughts on this problem are very welcome in the comments. How can the alignment be switched off by the developers?