[aprssig] Displaying Human Presence (was frequency)

[Robert Bruninga]

> You could expand on this, and have a PIR sensor 
> in the shack, so that any "Live" individual in 
> there triggers that, and so updates the
> stations presence settings.  

APRSdos has a person-present bit in position reports.  Presence
is detected by keyboard or mouse activity.  If a person arrives
in the shack and activity is detected, then the normal station
report is sent out now and the decay timer is reset to a short
period.

This alerts everyone reliablly that a human is present.
Eventually, with no human activity, then the posit beacon decays
back to the 30 minute rate eventually.  Similarly, APRSdos
displays stations with human presence in a different color than
those that have no human activity, so it is easy to see on the
map, who is worth trying to chat with.

The transmitted human-activity bit is encoded in the "case" of
the Latitude hemisphere.  "N/S" means human present.  "n/s"
means human activity not detected.  The idea is that APRS is
supposed to facilitate real-time communications between humans..
Not lights-on-nobody-home.

This is backwards compatible to most clients.  Uiview does not
recognize lower case "n/s" so the no-human-present stations
disapplear on a Uiview map until again they are again inhabited.

Bob, WB4APR