Location and distance calculation using Wifi in an

Question

How to get the distance of our mobile device from a wifi hotspot kept inside a building? This is basically for navigational purposes inside the building.. Any help would be appreciated.

Answer 1

Hi Kris

I understood what you are asking, The distance between Wifi access point and the Receiver, correct ? If yes, then it seem to be not possible after watching the discussion below.

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Answer 2

If you want to use WiFi for indoor location (step 1 before navigation), then distance to the WiFi Access Points is not the correct approach. Instead use RSSI.

With Android you would need to take WiFi fingerprint of a building by moving around every few meters and sample the RSSI strength. You need to provide a user interface that lets the user manually specify on an image of the building (e.g. a CAD drawing). Doing this will build up a database of what the RSSI is for different locations in the building. When you come to use this data for locating a user indoors, then you need an app to take the RSSI strength measurement and compare it against the database you've prepared to find the appropriate match.

Notes: - If anyone adds/removes access points, you'll need to resample the building - The measurements can be affected by density of people - Some access points are variable strength access points, so the RSSI fingerprint is not consistent. - This won't work with iPhone because there is no API to get the RSSI strength.

So, it is a useful, but not perfect way to get indoor location. There are a lot of more detailed articles on RSSI fingerprinting available.

Of course, navigation has to be built on to of that then.