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[aprssig] Commercial APRS-like Systems

Keith VE7GDH ve7gdh at rac.ca
Mon Jun 7 16:55:37 UTC 2010


Tim N9PUZ wrote...

> Are there commercial, APRS-like systems available? I know various 
> companies such as Qualcomm have fleet tracking, etc. but I was asked 
> this morning if I knew of anything available to the private sector with 
> similar features to APRS.

There are fleet tracking systems that use the cellular network. However
there is AIS which is used by ships at sea...

http://en.wikipedia.org/wiki/Automatic_Identification_System

However, it is based on a sophisticated technology called STDMA...
Self-Organized Time Division Multiple Access. It's a step or two
above "come as you are" with 25 year old technology. Often, it
is hams that lead the way. In the case of AIS, they are way ahead
of us. I'm still amazed that we can do what we can with really
old technology, but with STDMA and 9600 baud, ships can
theoretically have 4500 time slots per minute. Admittedly,
AIS is direct from ship to ship... i.e. no digipeaters involved.
However they do have the equivalent of receive stations and
IGates to gather all the data for use elsewhere. I haven't tried
to do the math, but perhaps with digipeaters involved (depending
on the number of them around you) you could still have many
hundreds of time slots per minute.

73 es cul - Keith VE7GDH
--
"I may be lost, but I know exactly where I am!"



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