[OZAPRS] Odd data path

[Andy Nguyen]

Hi Norm,

in Mic-E encoding, the X.25 destination address contains the encoded position, and some other data, in 7-bit printable ASCII characters:

- 6 latitude digits
- 3-bit mesg identifier
- N/S W/E indicator
- longitude offset indicator

for ST54S9:

- S = LAT 3, mesg bit A = 1
- T = LAT 4, mesg bit B = 1
- 5 = LAT 5, mesg bit C = 0
- 4 = LAT 4 N/S indicator = S
- S = LAT 3 long offset = 100
- 9 = LAT 9 W/E indicator = E

ie. latitude of 34 degrees 54.39 minutes South, in the Eastern hemisphere, message id = 1 1 0, ie. En Route
The longitude can be calculated from the long offset and information field.

The specs is documented here: http://www.aprs.org/doc/APRS101.PDF, page 44.

Regards,
Andy
vk3yt

On 14 Jun 2016, at 3:14 pm, Norm McMillan <vk3xci at gmail.com> wrote:

> ST54S9,VK5RHO-1,WIDE1*,WIDE2-2,qAR,VK5THB--5
> 
> The bit I don't understand is the ST54S9. I always thought that this defined the TNC device and usually starts with AP for APRS followed by a string to ident the tnc?
> 
> Now I look a little closer at the data-stream I see quite a few SWU1U4, S7T9Y5... hmmm all six element strings starting with S?
> 
> A brief explanation or link?
> 
> 
> norm
> vk3xci
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