Thread: tracking police gps

There is a fairly common way to track vehicles. Take the output of the GPS, create a packet using a TinyTrack (from Byonics) or something similar, transmit it over a ham radio frequency, and it's instantly available for all to see on the web. like this:

http://www.findu.com/cgi-bin/find.cgi?call=k7rkt-1

The most likely scenario (in the US anyway) is the use of Motorola MDT or RD/LAP data transmission protocol. Many police departments use mobile data terminals to send and receive dispatches and other data that would tie up the voice channels. Adding periodic GPS coordinate updates to this data stream is pretty simple if they're already have a deployed data network.

MDT (aka MDC4800) protocol is relatively easy to decode with a scanner and soundcard input. This was a blast 5 years ago, but now just about everyone is switching to the higher speed RD/LAP protocol which runs at 19,200bps. Because it's encoding method is more complex (4 levels vs 2) it hasn't (to my knowledge) been decoded yet.

Listen to 855.8375 for data. This is the ARDIS/Motient national frequency that many police/fire/ambulance/UPS/taxis have used in the past for their mobile data terminals. Your PD *might* be using this network and they *might* still be at 4800bps, in which case you *might* be able to decode the data stream.

Obviously even if you got as far as obtaining an ASCII data stream from an MDT channel you'd still have hurdles left to jump to get a map with little red dots all over town representing police cars.

Stop speeding and you won't have to worry about it. <grin>

-- divideoverflow

In the uk not only are they digitally encrypted but on channels that are not available to the public so a scanner is pretty useless nowadays.

With some creative soldering you can get a scanner to work in ranges it wasn't intended to.

Actually reading the data might not be necessary, if you could just locate the transmitter.

I wonder if they figured it out yet.
Guy's, the thread is 1 and a 1/2 years old........

Originally Posted by MGD

I wonder if they figured it out yet.
Guy's, the thread is 1 and a 1/2 years old........

Well don't look at me, I only responded cos it was in new posts.

Originally Posted by ElKeeed

Well don't look at me, I only responded cos it was in new posts.

03-24-2004, 05:35 PM

Great uptime on your computer

Originally Posted by MGD

Guy's, the thread is 1 and a 1/2 years old........

Does that make it not relevant now?

If we can't bring up old threads, what's the point of the search button?

-arebelspy

Originally Posted by arebelspy

Does that make it not relevant now?

If we can't bring up old threads, what's the point of the search button?

-arebelspy

Nothing wrong at all with bringing up old posts. I'm just wondering how it appeared in his new posts.