[aprssig] Traffic spec

Robert Bruninga bruninga at usna.edu
Thu Nov 20 15:00:02 EST 2008

> If I was to manually create and send a 
> SPEED-POST packet... how is the TO formatted,
> APRS, BEACON, or something else like APAGW?

To post a SPEEDPOST sign on the map at a given location showing
speed past that point, the packet in its raw format would look
like this when displayed in the common "TAPR-2" format:

Hdr:  WB4APR>APtfc1,DIGI1:
Data: ;50W-Bowie*120730/DDMM.mmN\DDDMM.mmWm270/015/{15}MPH at

Where WB4APR here is the AX.25 call of the sending TNC

Where APtfc1 is the AX.25 TOCALL. 
 (I made up APtfc1 for traffic version number 1)

Where "50W-Bowie" is the name of this signpost 
 (route 50 westbound through Bowie).

Where 120730/ is 0730 local time on the 12th

Where 270/015 shows traffic direction and speed (15 MPH)

Where {15} is the signpost-object format 
for what gets put on the signpost display symbol

And "at 730" is for the time of the data.

Notice that the time and the speed are redundant, this is
because there are two objectives:  1) To display the SIGNPOST
symbol on the map with a heading vector for those people with
APRS map displays and 2) to be useable to mobile operators who
only see the text on their mobile radio display.  Here is how it
looks on the display of the D7 HT:

 {15}MPH at

So all we need is a program to parse the readily available
traffic data from web pages, and then spit out the correct
packet with the correct location and informaiton, and then APRS
mobiles can see traffic speeds during their commutes and drive

Bob, Wb4APR

Hope that helps.

Bob, Wb4APR

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