[Xastir] New user..and thanks..

[Curt Mills]

On Sat, 18 Nov 2006, Jeff Mohler wrote:

> Ive just this moment finished making my first map, discovered that
> they have to be square in the process.

No they don't.  They need to be rectangular though for Xastir.  If
you two georeference points on the map, hopefully as close as
possible to two diagonal corners, then Xastir should be happy to
display it to you.  The reason for getting near the corners is
accuracy.


> 640x640 fit everything just fine.

You can use 1600x1200 if you like.  Or bigger.  Or some completely
different aspect ratio like 100x2000.  Doesn't matter.  For best
accuracy you want it to be in WGS84 or NAD83 datum, and
non-projected.


> I'll have to play with the options in the opentracker on the sending
> side, to see how I can most intelligently deal with near-real-time
> updates.  When in action, 30s is far too slow, but I dont see how 5
> vehicles could xmit updates every 5 seconds without lots of
> collisions.

Either set them up for SmartBeaconing with parameters that make then
transmit fast enough for you, which will allow them to somewhat
randomly change their timing as they go, or set them up for
timeslotting.  Unfortunately I think most of the trackers out there
aren't set up to transmit more often than once per minute using
timeslotting.

BTW:  Some collisions are ok.  Don't expect to get every
transmission.  If you set them up for non-timeslotting as in a
regular timed transmission or SmartBeaconing, set them up so that
you have a enough free time for all of them to transmit, plus double
or triple.  You'll get some collisions for each, but you'll get a
lot of positions out as well.  Hopefully that made some sense.

I doubt you're going to get updates every 5 seconds unless you're
running only one or two cars.  You may be able to get as fast as 2
seconds per transmission, across all the cars, so if you have 10
cars you might be able to get 20 second updates per car.  To get
each one transmitting in the clear you'd probably require custom
mods to the OpenTracker firmware, but Scott would know.

If you just have each car transmitting every 20 seconds with
fixed-timing (not timeslotting), then you have the chance of
collisions and you may not get updates for 40 seconds, or 60, or
even longer, from any particular car.

Another way to avoid this is to have each car on a separate
frequency, then base can have multiple receivers (a separate
scanner or radio per frequency) and get all of them in the clear.
Xastir can handle that just fine, but you'd need a separate TNC per
scanner or radio, as the soundcard driver (AGWPE) would only be able
to handle two radios.  If you had a system that was capable of
handling multiple soundcards, then _perhaps_ AGPWE could be run on
each one of them, giving you two radio channels per soundcard.  I'm
not a Windows guy so I don't know for sure.

-- 
Curt, WE7U.				archer at eskimo dot com
http://www.eskimo.com/~archer
  Lotto:  A tax on people who are bad at math. - unknown
Windows:  Microsoft's tax on computer illiterates. - WE7U.
The world DOES revolve around me:  I picked the coordinate system!"