On Thu, 04 Dec 2003 04:10:46 GMT, "Kevin Brooks"
wrote:


"phil hunt" wrote in message
...
On Thu, 04 Dec 2003 00:40:10 GMT, Scott Ferrin
wrote:

At least the US has control over Navstar. I don't know if they do
this or not but I don't imagine it would be impossible to say, deny
all service to a war zone except to those using such and such
decription.

Would it be technically possible to have a local positioning
system for military purposes? If it had lots of transmitters and
switched frequencies often, it would probably be hard to jam or
destroy.

Such systems have already been used for decades in the training arena. For
example, at FT Irwin (NTC), the maneuver area (a large area at that; some
350K acres when the system was originally set up) was covered with a
transmitter/receiver system that pinpointed the location of vehicles or even
manpacked locator transmitters, allowing the creation of a digital map of
each exercise for use in conducting the after action reviews (held in what
was appropriately called the "Starwars Room"). I believe that the latest
version of this system now uses GPS to provide the location data, though.

There is too much required work to establish such a system in a tactical
area. All of the points have to be carefully surveyed (and unless you use
GPS to do *that* then you are back to the old, slow manual survey loop)and
line-of-site considerations must be met. Then you'd have to worry about
redundancy, or else the loss of a single transmitter would be catastrophic.
At the pace of current operations, this is just not feasible.

GPS remains the best alternative, and remember that the "selective
availability" (SA) function remains capable of denying highly accurate GPS
usage to other parties within a theater of operations (without affecting
other worldwide users) if so desired (see http://www.igeb.gov/sa.shtml ).

Brooks


I don't imagine China and Europe would give the US that kind of
control over Galileo ;-)