[aprssig] APRS Formats, truncation or rounding?

Curt, WE7U archer at eskimo.com
Wed Jun 21 12:20:27 CDT 2006

On Tue, 20 Jun 2006, Curt, WE7U wrote:

> 1) Mic-E
> 2) Non-Compressed Standard APRS Format
> These two types of posits contain lat/long's down to 100's of a
> minute.  When creating the packets, what do the devices do with the
> remaining minutes digits?  Truncate?  Round?
> Both hardware devices and software can create these two types of
> packets, so this includes D7A's, D700A's, TinyTraks, OpenTrackers,
> other hardware trackers, all of the APRS clients, etc.
> Would we need experiments with each type of hardware/software using
> a GPS in simulator mode to determine this?

The experiment is as simple as putting a GPS into simulator mode and
"DD MM.MMM" format, then changing the last digits from .004 to .005
to .006 and kicking off a transmit for each.

Look up the positions on an APRS client or on FINDU to see whether
the device or software truncates/rounds when generating the posit.

Curt, WE7U.   APRS Client Comparisons: http://www.eskimo.com/~archer
"Lotto:    A tax on people who are bad at math." -- unknown
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