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Topic: Arduino WiFly Triangulation (Read 2656 times) previous topic - next topic

MadDawgScientist

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

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)

MadDawgScientist

How do I pull RSSI data from the WiFly?

zoomkat

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.

http://www.youtube.com/watch?v=AUzkiIB4QZ8
Google forum search: Use Google Advanced Search and use Http://forum.arduino.cc/index in the "site or domain:" box.

MadDawgScientist

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

retrolefty


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


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