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Homebrew GPS tracking device?

  1. Sep 2, 2012 #1
    I was looking through some recent catalogs from electronic stores and a new thing they are trying to hitch is the GPS car tracking devices. There is a major flaw in the system for anonymity, you have to register with a " air time" service to add tracking days and such.

    For 139 dollars I was intrigued. I remembered I had an old Garmin Gps that I used to walk around the mountains.

    Would it be possible to turn that into a tracker that could be pulled up on a computer screen or something?

    I think with a little know-how it can be done.

    No doubt this will get flagged for illegal activity discussion.

    At least they keep this place clean.
     
  2. jcsd
  3. Sep 2, 2012 #2

    Bobbywhy

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    Gold Member

    As far as I understand the Garmin GPS is completely passive. That is, it receives signals from several satellites and gives you your lat/long. There is no signal transmitted, and there is no way a passive receiver can be detected.

    In order to track a moving object (car, for instance) it would be necessary to transmit something to get detected by the satellites or other fixed receivers.

    Cheers,
    Bobbywhy
     
  4. Sep 3, 2012 #3
    If you need to do the tracking real time, it gets a little messy. You might have to encode the GPS output onto an audio signal and transmit it by cellphone. (You'd need a way to keep the cellphone's battery charged.)

    Non-real time tracking would only require a way to store the time and data on a memory chip.
     
  5. Sep 3, 2012 #4

    berkeman

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    Staff: Mentor

    This is done with HAM radio all of the time. It's called APRS, and you tie your GPS to your HAM radio -- your position is sent via HAM radio to whatever tracking software you choose to use. It's very handy when you have a bunch of HAM radio operators helping with bike races and similar events, spread out over the countryside:

    http://en.wikipedia.org/wiki/Automatic_Packet_Reporting_System

    You need a HAM radio license (and APRS-capable HAM radio), but that's easy to get now. There may be other ways to accomplish what you want, without using HAM radio, though.
     
  6. Sep 5, 2012 #5
    The GPS coordinates probably spit out of the GPS receiver inside your garmin on a USART unless the receiver and microcontroller are combined. You could solder into these data lines and record/parse the data with a microcontroller, and then later download it onto your computer with some serial interface like USB. You might also need to disable battery saving features in the receiver since the Garmin microcontroller will be communicating with it. You would have to power it all with a battery. It won't be real time and will require some significant effort, but it will log coordinates. If you want remote real time access, the HAM radio idea is good or use a gsm modem that downloads to a server like the device you saw probably has. With all of that effort, you probably would save time and money just buying what they made or designing your own device.
     
    Last edited: Sep 5, 2012
  7. Sep 5, 2012 #6

    es1

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    I don't know how feasible it is to hack a Garmin but it is possible to build a completely homebrew GPS. Personally I found this fascinating. It's definitely not a project for the feint of heart though.

    http://www.holmea.demon.co.uk/GPS/Main.htm
     
  8. Sep 6, 2012 #7
    Or try to get a hold of one of Progressive insurance's SnapShot modules.
     
  9. Sep 6, 2012 #8
    You can buy a lot of that stuff integrated on an IC. The front end and everything to the interface to your digital circuitry comes in hybrid packages from companies like Trimble. You just have to design the antenna trace impedance mostly and then your FPGA/whatever. So, that at least would be 1 short cut.
     
  10. Sep 10, 2012 #9
    The trick is the communicaiton channel - HAM works, but I do not know how small of a HAM transmitter you can get. I think cell phones actually can be anonymous if you buy a pre-paid one - then send data via SMS.

    Also - Sparkfun has a bunch of GPS modules and a small arduino - may be easier then hacking a consumer device.

    Etherway - this can surely be done, but will involve working on a number of different things...

    An interested related project....http://www.chriscoldewey.com/2008/05/11/tracking-deer-on-google-earth/
     
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