Alerting system for a person-of-interest

Projects General Guidance
1

I would like to make a system through which i can be alerted of the presence of a person if he comes within a radius of say 50 m of where i am located. Also, i should be able to know the direction and distance of his location from mine.

The most basic idea is to use a signal receiver-transmitter system. A transmitter would be mounted on the person(or maybe his car) and the i would be carrying the receiver which can be interfaced with an Arduino, which would alert me as soon as the person enters a certain zone around me.

My biggest problem at the moment is choosing the correct transmitter-receiver. Since we are talking about distances around 50 m(164 feet) i think i would need a radio transmitter-receiver. But i have not used any of those before and i am not sure which device would be a good fit for this project. Also i would like to be able to tell the distance and direction of the person-of-interest.

I would be very grateful for any sort of ideas regarding the transmitter-receiver device. I am also open to suggestions if the project can be done in some other way.

2

The easiest way is to use GPS and transmit the data wirelessly.

You could create a proximity sensor by using a RF module system that has RSSI (Received Signal Strength Indicator.) You can get a rough estimate of distance by the strength of the received signal. Using three modules (or switched antennas) you might be able to triangulate the direction.

But, personally I would use GPS for this application.

3

Are we talking indoor or outdoor?

4

inventorArtist:
Are we talking indoor or outdoor?

Yeah we are talking outdoors mostly. But it should work anywhere basically.

5

These solutions assume the other person is a willing participant who already has the appropriate equipment. Why not ask him/her to shout "Hello" and use use the human body's inbuilt sophisticated audio equipment?

...R

6

Yeah, I think it would be helpful to know the details of the project (situation, constraints) or objective to be able to help.