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### Topic: Arduino WiFly Triangulation (Read 4066 times)previous topic - next topic

##### Apr 28, 2011, 06:29 pm
Hi. all.

I'm working on a project that uses Wifi triangulation in a path-finding algorithm to move a wheelchair from point A to point B.

I'll need to know the position of both A (the wheelchair in realtime) and B (the destination), given the RSSI from two different routers (I think that's how it works?).

However, I'm not entirely familiar with how to actually implement triangulation using the WiFly on the Arduino (Duemilanove ATmega328).

If someone could point me in the right direction I would greatly appreciate it. My programming experience is minimal.

#### robtillaart

#1
##### Apr 28, 2011, 06:41 pm
You must see the RSSI signal strength as the (reciproke) diameter of a circle The stronger the signal the smaller the diameter.

You have two circles and they intersect each other in two points and one of the points is you

Check - http://paulbourke.net/geometry/2circle/ - for the math

However be aware that due to reflections and variations in signal strength you will have limited accuracy. It works not as nice as in some movies
Rob Tillaart

Nederlandse sectie - http://arduino.cc/forum/index.php/board,77.0.html -
(Please do not PM for private consultancy)

#2
##### Apr 29, 2011, 04:00 am
How do I pull RSSI data from the WiFly?

#### zoomkat

#3
##### Apr 29, 2011, 04:48 am
There have been numerous post in the past concerning using RF signal strength to determine bot locations. Don't ever remember a workable setup being posted. The below might show how the wifi strength can vary independent of distance from the source.

Why I like my 2005 Rio Yellow Honda S2000  https://www.youtube.com/watch?v=pWjMvrkUqX0

#4
##### Apr 30, 2011, 12:52 am
So there's no way to get RSSI values from the WiFly using the Arduino?

#### retrolefty

#5
##### Apr 30, 2011, 01:28 am

So there's no way to get RSSI values from the WiFly using the Arduino?

Sure, electrically it can be done. However what we are saying is that the fundamental RSSI signal will never be precise enough to do meaningful triangulation, just too many peaks and nulls and reflections to confuse any triangulation algorithm.

Lefty