Pages: [1]   Go Down
Author Topic: Arduino WiFly Triangulation  (Read 2445 times)
0 Members and 1 Guest are viewing this topic.
Offline Offline
Newbie
*
Karma: 0
Posts: 4
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

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.
Logged

Global Moderator
Netherlands
Offline Offline
Shannon Member
*****
Karma: 216
Posts: 13666
In theory there is no difference between theory and practice, however in practice there are many...
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

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 smiley-sad
Logged

Rob Tillaart

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

Offline Offline
Newbie
*
Karma: 0
Posts: 4
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

How do I pull RSSI data from the WiFly?
Logged

0
Offline Offline
Tesla Member
***
Karma: 141
Posts: 9549
Arduino rocks
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

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.


 
Logged

Consider the daffodil. And while you're doing that, I'll be over here, looking through your stuff.   smiley-cool

Offline Offline
Newbie
*
Karma: 0
Posts: 4
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

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

Left Coast, CA (USA)
Offline Offline
Brattain Member
*****
Karma: 361
Posts: 17293
Measurement changes behavior
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

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
Logged

Offline Offline
Newbie
*
Karma: 0
Posts: 4
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Ok. Thanks, all!
Logged

Pages: [1]   Go Up
Jump to: