Is there a technology that can pinpoint an iPhone's *exact* location (to the feet/couple feet, indoors)?

Question

Is there is a way to determine an iPhone's exact location (indoors, and to a distance of just a couple of feet) via use of radio/antenna's or some other infrastructure located around premises (i.e a hospital, shopping mall, school). Will appreciate any ideas/direction (technologies, research) as for how to overcome this limitation.

Answer 1

If you mean for an area you have control over (setting up a location network for a specific school/hospital) as opposed to generic location, you'd be able to triangulate your position based on wifi signal power for APs with known locations.

If you wanted it to be a generic solution, and you know there would be multiple APs in/around the buildings you wanted, you could triangulate all wifi signals while you have GPS outside the building, and then reference those locations when you lose gps accuracy. The first part is something that many wardriving applications already do.

Here's an article describing a commercial technology for this purpose in high-level detail: link

And here's a link to a SO page where people have started discussing possible methodologies: link

Answer 2

Use the GPS and hope that you got good coverage.

Other than this, you can deploy several wifi hotspots that can measure the signal strength for each packet and do a triangulation to calculate the iPhone position with regards to three or more of these hotspots based on the signal strength each of them measured.

A quick search for "signal triangulation" on the internet reveals a Wi-Fi Based Real-Time Location Tracking technology from Cisco. I have not used it, so I can't vouch for it; and I suspect it's rather expensive. There might be other solutions as well.

The alternative would be to buy several wifi routers or access points and flash them with your own version of the firmware. You can probably use OpenWRT or DD-WRT as a base for this.