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topografix

Explain APRS?

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Can someone explain the basic principles behind location tracking using APRS? Here's the situation where I'd like to use APRS:

 

I'd like to use APRS to transmit the location of a moving vehicle (or better yet, a roving geocacher) back to a nearby base station, and extract the location data for use in my own software. (http://www.expertgps.com)

 

As I understand it, the tracked person carries a GPS, a radio, and some sort of device to connect the two and broadcast GPS data over the radio.

 

I don't understand the base station setup at all. Can someone clue me in? I assume there's another radio, a serial port connection to the PC, and some software that listens to the data stream coming off the radio and plots it on a map. Since I'd like to integrate this with my own mapping software, I'd like to find documentation of that data stream. Any specific pointers?

 

Can someone explain how FindU and other web tracking services tie into all this? How do they get the position of my mobile geocacher? Is the base station software supposed to notify the website, or do the notifications just propagate out over the APRS network until the FindU base station picks them up?

 

Thanks in advance,

 

--

Dan Foster

TopoGrafix: GPS Software, Waypoints, and Maps

http://www.topografix.com/

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If you are able to intergrate APRS into ExpertGPS. That would be awesome!

 

I'm no expert in the software part of APRS, but basically its just a simple ASCII text string that contains basically; your callsign, a destination callsign (or how it should be routed), and a short msg (Lat&Lon, Wx info, or text).

 

If you have a radio scanner that you can hook up to your soundcard. You can decode the packets with www.raag.org/sv2agw/ AGWPE.zip A common freq is 144.39 MHz. There are also a number of places on the internet to get live feeds of the APRS data. But, I really don't know how to access them other than through the WinAPRS program.

 

Also, a good webpage to look at for info would be the creator of APRS Bob Bruninga, www.aprs.org

 

The Tucson Amateur Packet Radio site (www.tapr.org) should have all the technical information you need, as well as, a email list in you need any more info.

 

I would really like to see your APRS enabled program when you finish.

 

Hope that helps.

William, KD7JJY

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quote:
Originally posted by TopoGrafix:

Can someone explain the basic principles behind location tracking using APRS?

Thanks in advance,

 

--

Dan Foster

TopoGrafix: GPS Software, Waypoints, and Maps

http://www.topografix.com/

 

Dan,

You have the fundamentals of APRS down just about right. The AGWPE program mentioned above can accept the data stream from a ham receiver via the computer's sound card and make the data available to other programs via TCP/IP. Check out http://www.qsl.net/soundcardpacket/ for more information.

 

Lou Catozzi

TxHiPowr

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There are a couple of radios on the market that will take the output from a GPS (in NMEA format) and beacon this as an APRS transmission.

 

The one I have is a Kenwood TH-D7E (in the USA it's known as the TH-D7A) which is a hand portable radio. The other one is the Kenwood TMD700, which is designed to be mounted in a vehicle, or at home.

 

For quite a while, I've used a program at home called UI-View (see http://www.ui-view.com/) with a device known as a Terminal Node Controller, or TNC, which outputs the required audio to a normal transceiver. However, out walking, this can be a pain to have to cart around.

 

You will need an Amateur Licence to transmit on the Amateur bands, of course. The only other way would be those Rhino radios, which I think are licence free in the USA.

 

--... ...--

Morseman

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I've had the TH-D7A for 4 years now and didn't know it would do that. Guess its time to get out the ol' users manual.

 

Time Flies like an arrow. Fruit Flies like a banana

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quote:
Originally posted by ikayak:

I've had the TH-D7A for 4 years now and didn't know it would do that. Guess its time to get out the ol' users manual.


 

I've now managed to get the PC and the TH-D7 talking to one another. icon_smile.gif

 

Watch out for the manual, the diagram showing the minature stereo plug is showing the outputs from the TNC *not* the connections to make to the 9 pin D for the COM port!

 

Look just below the picture of the stereo plug for the connections to the 9 way.

 

I hope to be beaconing with UI-View from home tonight.

 

Oh, if you want, you can use a Packet program, such as WinPack (same author as UI-View) to let you connect to a BBS on air.

 

--... ...--

Morseman

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quote:
Originally posted by ikayak:

I've had the TH-D7A for 4 years now and didn't know it would do that. Guess its time to get out the ol' users manual.


 

I've now managed to get the PC and the TH-D7 talking to one another. icon_smile.gif

 

Watch out for the manual, the diagram showing the minature stereo plug is showing the outputs from the TNC *not* the connections to make to the 9 pin D for the COM port!

 

Look just below the picture of the stereo plug for the connections to the 9 way.

 

I hope to be beaconing with UI-View from home tonight.

 

Oh, if you want, you can use a Packet program, such as WinPack (same author as UI-View) to let you connect to a BBS on air.

 

--... ...--

Morseman

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