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June 09, 2008


Owen Stephens

But what does GPS add over the current 'triangulation' service already available. Clearly a slightly more accurate location, but in terms of Geotagging photos, how accurate is really important? For location based services like 'show me the nearest', the triangulation would seem good enough as well.

It just seems to me that the important thing here is not GPS, but the ability of other applications to access location data from the device (GPS or triangulated) - and presumably those who have the software development kit for iPhone already know whether this is possible or not?

Richard Akerman

There are two other techniques for location determination:
1. Use cellphone tower information
2. Use wifi node information

If I understood Steve correctly, Google Maps on the current iPhone mainly uses wifi node info.

Both of these have a huge disadvantage in that they require you to gather tremendous amounts of information in advance, and they don't handle changes well. Presumably they were able to gather enough info to cover most of metro US acceptably, but I don't see how this can possibly scale to covering the entire world. GPS gives you a much more accurate location anywhere in the world it can see enough satellites, with zero information update or maintenance cost.

Because of that, I think that Location Services will get a much bigger push if the iPhone has GPS. I don't know how reliably you could do road nav using just celltower locations, for example.

glen wood

@Richard Akerman

you can't do road nav by celltower triangulation - at least not anywhere I have tried, throughout the Midlands in the UK. In my city, the iphone is usually inaccurate by 0.5 to 1 mile from my actual position.

but then the iphone is very US-centric (and probably very metro-centric within that). It misses lots of features that every phone user in Europe takes for granted (my friends almost refuse to believe me when I tell them some of the stuff thats wrong/missing with the iphone) and includes features that seem useless. I guess it's aimed at bay-area or NYC hipsters, and the rest of us have to like it or lump it.


i like my photos to be geotagged to within a couple of yards accuracy - 10ysrds min. Recording the heading would be good too :)

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