Sensor Node Localization

[wowowee]

Hello Everybody,

I would like to implement a sensor node localization through the use of a PIC16F877 microcontroller and ultrasonic waves to calculate the distance.

Here are steps of what I would like to implement:
1. I have 4 nodes, each having an ultrasonic rx/tx, a radio frequency rx/tx and a PIC16F877 which serves as the brain to each node . 1 node is interfaced in the personal computer w/c could be called as the base node or the beacon. The other 3 nodes are called the listeners.
2. Here is what I would like to happen; When the 3 listener nodes are relocated, the computer then displays the real-time orientation of the nodes. The computer has this data through the base node which is interfaced with the computer.

My question then is, how am I be able to measure the distances between each of the nodes?

Thank you very much in advance...

 

[penoy_balut]

you have to make four fixed beacon, each one capable of interrogating your listeners, then process those four distances gathered to calculate relative positions.

 

[wowowee]

Ahhh...ok, i get your point...But I want my implementation to have 1 beacon/base node which serves as the reference point or the origin. The whole system would only localize if at least 3 listener nodes are placed all together on the arena. The base is the one to calculate estimated local coordinate system of the 3 listener nodes...I know this is possible 'coz I've seen a very similar scenario but was not implemented with a PIC16F877 and yes, it was a very expensive approach.Could you help me on how to calculate estimated distances using TDOA or other similar approaches?
Anywayz, thank you very much kind sir....