Positioning Demo

A project log for SubPos Positioning System

A "dataless" Wi-Fi positioning system that can be used anywhere GPS can't.

Blecky 05/03/2015 at 02:580 Comments

Here is a quick and dirty demo video to show off the completed system as it stands so far. The red markers are the known node positions (which are taped to the wall in the video) and the blue marker is the trilaterated position (where the phones are on the table). The nodes themselves are located around the room as you can see in the video.

The node GPS position is "faked" for obvious reasons, but the demo is live. You will also notice at 37 seconds that one of the phones is still waiting to get a beacon frame as the sampling rates differ between phones, but it eventually gets there (as I scroll around you see it go from 3 nodes to 4 nodes and the position then changes). The algorithm itself is performing an averaging function to smooth out the calculated distances from the path loss as well, but you only notice this when moving about.

The position of these nodes is too close to actually be that useful due to the inherent error in the system at the moment (about 1-2 meters so far), I am still working on getting this lowered with faster polling and beacon transmit rates (custom AP firmware) as well as better averaging. I will test more nodes across a larger area as well as more nodes with lower power at some stage when I get some time as well. The current Android application is capable of obtaining a rough position estimate from even just a single node (the position of the node and the radius/error).

Edit: the app binary has been uploaded here if anyone is interested in testing it. I will get an SDK available in the next couple of weeks.

Here is the positioning data I used for those interested, the room I was in is 370x370cm and the GPS coordinates correspond to this:

Square: 370x370cm

Elevation 3200cm

Window Side
NE - A(1) - -37.8107630, 144.9623010
SE - B(2) - -37.8107940, 144.9623150

Kitchen Side
NW - C(3) - -37.8107750, 144.9622620
SW - D(4) - -37.8108060, 144.9622760

Device ID    : 1

Device ID    : 2

Device ID    : 3

Device ID    : 4