[aprssig] Can objects/items dead-reckon?

Tom Russo russo at bogodyn.org
Mon Feb 27 10:48:50 CST 2012

On Mon, Feb 27, 2012 at 04:12:35PM +0000, we recorded a bogon-computron collision of the <andrewemt at hotmail.com> flavor, containing:
> Greetings, all.
> I was looking at the spec regarding Objects and Items, and it's not clear whether a station sending such APRS messages can add a course and speed for Objects.
> Can course and speed be specified for an Object? I would presume so, given the stuff about tracking storms/hurricanes/etc., but can it be done for generic Objects?

Yes, objects can have extended data such as course and speed.  See page
58 of the APRS 1.1 spec document, where there's even an example of that.

> If Objects can have a course and speed, is the sending station and/or the receiving stations supposed to dead-reckon the future position of the Object based on that course/speed? If so, how long should such dead-reckoning be carried on before the original position/velocity report is considered too stale to continue extrapolating?

The receiving station dead-reckons positions.

I don't know what other clients do, but Xastir has a user-configurable
dead-reckoning timeout.  The observing user decides what the staleness cut-off 

Tom Russo    KM5VY   SAR502   DM64ux          http://www.swcp.com/~russo/
Tijeras, NM  QRPL#1592 K2#398  SOC#236        http://kevan.org/brain.cgi?DDTNM
"And, isn't sanity really just a one-trick pony anyway? I mean all you get is
 one trick, rational thinking, but when you're good and crazy, oooh, oooh,
 oooh, the sky is the limit!"  --- The Tick

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