Just to make sure I understand the 'ground rules', the three base stations define a plane, unless they are on the same line. Is the mobile device also in this plane? How far apart are the base stations relative to the location of the mobile device? Or, better, is the mobile device 'inside' this triangle or 'outside'?
How precisely can you know the location of the base stations without violating the 'inexpensive' rule? Can the base stations 'ping' each other? Seems to me that an accuracy to 3 feet is going to be a problem without precise time measurement unless you can use some 'known' reference (like the precise location of the base stations) and the ability to use that 'known' to 'calibrate' each measurement, thus minimizing the errors from 'drift', etc., in the available, 'inexpensive', time references. Good luck. Joe -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Rick Harold Sent: Thursday, January 31, 2013 10:37 PM To: [email protected] Subject: [time-nuts] question for expert time guys To time experts/EE's. I would like to triangulate a position of a device which moves using 3 fixed positions devices of known location. The idea is to have these operate on 915mhz or 434mhz or 2.4ghz or appropriate frequency. These two type of devices (fixed and mobile) are all under my control and thus customized as needed. The mobile device (not a phone, custom device) would be the least expensive item. I'd like a range of 150 feet or better and accuracy of 3 feet or better. When manufactured these items they can be calibrated in order to adjust for any variation in IC's, discrete components etc... We can assume for now the temperature is constant 70 degree temperature. Cost is the key design factor. The general flow is: 1. base station 1 indicates we are determining position of device A. 2. Each base station 1, 2, 3 take turns pinging the device to determine distance. 3. A ping consists of (something like, e.g. frequencies as examples) -send 915mhz signal from base station to device -device response ASAP on different frequency -station waits and counts 'time' for return -this is repeated N? times to get best avg/accuracy. -The mobile device does not move very fast 4. Since delays of the process on each unit is calibrated the device and base station would subtrack that time out from the results. 5. obviously with 3 distances we can determine the 2D position of the mobile device I know the time accuracy is the key to count time = feet, 1ns. This overall project is not new concept. How to make it "inexpensive" is key. how inexpensive, very ;-) no OCXO or expensive components like that. That's my goal, and I'm looking for help on the design/thought process of getting there. I am open to a consulting arrangement for a fee, please email if you like. I've worked with 'regular' EE's (I'm a software guy) but this time accuracy is too much for them. Esp. finding a way to do it inexpensively. Thanks for any thoughts. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
