How to implement indoor navigation on the iPhone

Question

I would like to locate the iPhone in a building to build an application with similar features as the iPhone app of the American Museum of Natural History. There is no good GPS reception as there are also rooms in the cellar I would like to cover.

What can save me is that there is good wifi coverage in the whole area, so my idea was to triangulate the position based on the wifi base stations in range, whose positions are known. However I found no public API to find out which base stations are in range.

Questions

1. Do you have an idea how the app mentioned above manages to get the correct location indoors?
2. Could one add the wifi base stations manually to Apple's database and use the usual CoreLocation?
3. Do you have other ideas how to implement it?

Any help is very much appreciated!

Boundary conditions

1. The indoor navigation is only used during an event to guide guests new to the building, so no complex infrastructure should be installed.
2. There are approximately 14-18 rooms to be covered. They are in different parts of the building, so wiring everything up would be very costly.
3. The preferred solution would not require a server backend of any kind and would work with a list of wifi access points and their corresponding locations.

Answer 1

I wouldn't know about 1 and 2. But if you would implement such a thing, turn it around to save a lot of trouble: create your own free-of-charge wifi network, and let the network determine the location, either based on triangulation, or just based on the currently associated access point. Make their signal weak so you have one audible access point per room. Let the app ask a server in what room he appears to be. This will also work for any other mobile/pda/laptop.

As for other ideas: You could use bluetooth to do somewhat the same as you're planning for wifi. You can't do everything with bluetooth, but listing devices seems to be one possibility. So just put a bluetooth device in every room. Bluetooth range is limited by definition.

Another one would be to use the microphone in conjunction with a high pitched sound which identifies the room, but that would cause trouble with dogs (for blind people), attract bats, and repel mice at the same time. Better focus on an RF based solution ;-)

Answer 2

Check out wirelesswerx.com THey seem to be doing indoor location using Bluetooth and it looks like they can do permanent install or temporary for events...