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[aprssig] USNS and APRS

Wes Johnston, AI4PX wes at ai4px.com
Mon Jun 1 11:26:13 UTC 2009

Let's say that I use the B0 format to specify 10 discrete positions.  Let's
say 100 people show up to my event.  Does the software dither the positions
slightly, or does everyone at a particular location "stack up" on top of one


On Mon, Jun 1, 2009 at 06:02, Bob Bruninga <bruninga at usna.edu> wrote:

> >Bob, any thoughts on using USNG with APRSTT?
> The beauty of APRStt is that it is a LOCAL system, SIMPLEX rnage only from
> the sender.  Thus, each APRStt is set up to match the needs of its users
> (usually one club) and this is independent of how APRStt might be used
> somewhere else.
> And APRStt can use any grid system, lat/long, SAR GRIDS, Mile marks, and
> even flea-market spaces at Dayton.  And any one APRStt can support many of
> these at the same time if needed.
> At our first system in Dayton, we defined the position format to be Bxy*
>  Just one digit in X and one digit in Y.  But the spec has always said there
> would be xxyy, xxxyyy, xxxxyyyy versions for greater precision, or greater
> coverage area.
> So after dayton, we formalized this as follows.  There are 10 possible
> Position formats that can be implemented in any instance.  In most cases,
> only the one that is applicable at any parcicular APRStt will be used.  But
> that does not prevent the engine from accepting more than one if needed.
>  Here are their definitions:
> B0x*        One of 10 special positions
> B1xy*       1 digit XY  ( 10 mi in 60 mi area) (default)
>                       (or 1 mi in 10 mi area)
>                       (or.1 mi in  1 mi area)
> B2xxyy*     2 digit XY   ( 1 mi in 60 mi area) (default)
>                      (or .1 mi in 10 mi area)
>                      (or 60 ft in  1 mi area)
> B3xxxyyy*   3 digit XY  ( .1 mi in 60 mi area) (default)
>                      (or 60 ft in 10 mi area)
> B4xxxxyyyy* 4 digit XY  ( 60 ft in 60 mi area) (default)
> B5zzzmm*    at bearing zzz range mm miles
> B6EEENNN*   SAR UTM Grid - Easting and Northing
> B7RRRMMM*   Road RRR, Milemark MMM
> B8......*   Table interpolation
> B9...   *   TBD
> What we used at Dayton is now B1xy*.  This added digit also is kind of a
> redundant check to make sure the proper number of digits has been received
> for a given posit.
> Back to the original question,  So what each XY grid represents and how
> much precision is independent of whether it is UTM or LAT/LONG or USNS.
>  That is established at se-up time at that location.
> Again, dont panic at all the options.  Usually, only one format will be
> used in a given applcation depending on the area covered and the degree of
> precision desired.  At Dayton, we only used B1xy*.  At the 2010 Scout
> Jamboree, we will use B2xxyy* because the published map that will be in the
> hands of every scouter will have an XX YY grid already on it.
> Hope that helps
> Bob, Wb4APR
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Where there's silence, there is no Hope.
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