From: johne@vcd.hp.com (John Eaton)
Subject: Re: Can Radio Freq. Be Used To Measure Distance?
Organization: Hewlett-Packard VCD
X-Newsreader: Tin 1.1 PL5
Lines: 26

Robert G. Carpenter (rgc3679@bcstec.ca.boeing.com) wrote:
: I'm wondering if it's possible to use radio waves to measure the
: distance between a transmitter(s) and receiver?
: 
: Seems to me that you should be able to measure the signal strength
: and determine distance. This would be for short distances (2000 ft),
: and I would need to have accuracy of 6 inches, or so.
: --------------------
You might try looking at whats available in laser locating systems. They
work best for close work( 1 mile and under).

RF is used for much longer distances in two major modes. Transponder and
phase measurment. Transponder requires you send a pulse to another station
and it returns it to you and you measure the round trip time minus the
receiver time.

Phase measurements require two or more transmitting stations sending the
same frequency signal multiplexed in time. A receiver can pick them up and
measure the phase shift between signals. Maps can be drawn that plot the
Lines of Position that correspond to a certain phase shift between two
stations. 

John Eaton
!hp-vcd!johne