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From: REM%MIT-MC@sri-unix.UUCP
Newsgroups: net.space
Subject: re: G.K. O'Neill's satellite plan
Message-ID: <16109@sri-arpa.UUCP>
Date: Sat, 28-Jan-84 16:27:00 EST
Article-I.D.: sri-arpa.16109
Posted: Sat Jan 28 16:27:00 1984
Date-Received: Thu, 2-Feb-84 01:00:05 EST
Lines: 38

From:  Robert Elton Maas 

Let me step back and analyze this system from an abstract viewpoint.

Why would anybody want to know their position (relative to a coodinate
system fixed on the Earth; as we all know absolute position is either
nonsense or useless as the Earth spins thru space) anyway??

To establish rendezvous with some desired target (a fixed object or
somebody else who you're trying to meet), to prevent rendezvous
with some undesired object (a hazardous area), or to estimate distance
between the current location and a potential target to determine
feasibility of rendezvous, or to find the set of all potential targets
within some prescribed radius. Following a route on a computerized map is
merely a combination of using the navigation system to get a direction
vector to achieve approximate rendezvous with the next map target, and
using local feedback to avoid local obstacles and to improve the
proximity of rendezvous, this procedure being followed over and over
for different intermediary rendezvous points along a route.

Can anybody think of any other fundamental use for a locator system?

In the woods/mountains, getting within a few hundred meters should be
sufficient. When your two locators say you are "at the same location"
but you still can't see each other, you shout or fire a gunshot or use
a local radiobeacon or radio-describe landmarks. In a crowded city you
need more accurate information, both because normal city noises tend to
drown out your shouts and the like, and because gunshots tend to
disturb the residents and the police. It would be nice if a single
system could handle both country and city, but perhaps cellular radio
in cities will do a better locator job anyway, as well as provide
other services that are too compute-intensive for the satellite to
handle (the satellite would have to handle a whole world's load
whereas the corner radio-cell-transceiver would have to hande only one
square block's worth of load, about 9 orders of magnitude less), so
maybe a dual city/country system is inevitable and having the
satellite accuracy be insufficient to handle crowded cities is a minor
inconvenience?