Question

How would I go about figuring the position of someone inside (or outside) of a given area (such as a building) using assisted GPS with IOS app?

• Is it possible to have it accurate enough withing a few feet?
• Is this the right way to go about it?
• Is it possible to utilize more than one wifi connection in the calculation?

Answer 1

Your app can use the Core Location framework to determine the device location. Core Location will use whatever hardware is at its disposal to determine the device location to the degree that you request. For example, some devices have WiFi but no GPS; others have WiFi, GPS, and cellular radios. Future devices may have other location technologies built in.

The point is that as an application programmer, you don’t worry about that. Instead, you say: “give me a location that’s accurate to 100 meters” or “let me know when the device has moved from the current spot by more than 10 meters” or “give me the location with the best accuracy you can manage.”

Again, take a look at Apple’s Core Location documentation to get a better idea of how it all works.

If you’re looking to track a device with, say, 1-meter resolution inside a building, you’re not likely to get that from Core Location. There’s been research on triangulating position using known locations of WiFi transceivers, but nothing that’s implemented in any commercial smart phone that I know of. I don’t believe that iOS gives you easy access to the data you’d need to do this, so it’s probably not a possibility. You could, however, go the other way: program several WiFi receivers around the building to listen for any nearby devices, use that information to triangulate the devices’ positions, and then make that information available via some web service.