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I played for a while with the maps framework from the iphone os sdk and the routemap api from cloudmade and it was fairly easy to display the current location and other information on a map by using the data provided by the GPS.

I have the map of a building(airport, mall etc) transformed in tiles of some sort, my question is what would be the best approach to obtain the current position of a phone inside a building? I know that GPS is not accurate inside buildings or might not work at all.

animuson
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Sorin Antohi
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4 Answers4

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Unless you have a strange sort of building (i.e. radio transparent roof), you will not get a GPS signal inside the building, unless you are close to a window, which there are usually very few of (in a mall anyway).

You will not get useful positional information from cell triangulation (not at mall/airport terminal scale anyway).

I'm afraid I can't see any way to do what you are trying.

EDIT: come to think of it, some malls do have a glass roof, so it might be possible to get a GPS fix in some places. And some small airport terminals have big glass walls, although you'd be unlikely to want a map if they were very small.

Colin Pickard
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  • Hello Colin, initially i was thinking about inserting some bluetooth receivers inside the building but that will not work in general.. during my googleing for a solution i bumbed into these guys http://www.micello.com/ they have an free iphone app in store but i can't find any details about their aproach :( – Sorin Antohi Jul 23 '10 at 13:24
  • Looks like the Micello people don't have any mechanism for getting the current position. Essentially all they have is a .png and some POI data. – Colin Pickard Jul 23 '10 at 13:47
  • @ColinPickard, can you please elaborate on why one would not get positional information from cell triangulation? – Maksim Sorokin Dec 18 '12 at 20:02
  • cell triangulation is too inaccurate to use within a single building, even a very large building such as an airport. An error of 1/4 mile would put you at least in the wrong terminal, if not outside the airport itself. – Colin Pickard Dec 20 '12 at 00:05
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If you are able to install a few WiFi nodes inside a building, you can get your location inside this building with Navizon's Indoor Positioning System. They have a demonstration video of their indoor navigation solution on an iPhone.

Emily S.
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Indoor Atlas maps magnetic fields in buildings and then uses smartphone magnetometer data to geolocate indoor locations to within 2 meters. It's based on the fact that buildings have predictable magnetic fields due to the materials they are constructed with. It's the best solution I've seen for this. You can try it for free as see if they've mapped the particular buildings you're trying to geolocate inside of. Another solution I've seen requires bluetooth devices within the building to assist with the geolocation, not as good because of the infrastructure requirements.

iepathos
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Since you can't use GPS or Cell towers, you'll need some other sort of RF sources, that have known positions (as GPS and Cell Towers do) Perhaps that's what you're targeting anyway, something like a mall or airport with a number of WiFi routers in known locations, that you could "ping" off. It's not that simple of course --- an interesting research paper on such a service is at Microsoft Research: In fact they write about possible applications such as malls or airports.

Ralph Shillington
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