Path: utzoo!utgpu!watmath!clyde!att!cbnews!henry@zoo.toronto.edu
From: henry@zoo.toronto.edu (Henry Spencer)
Newsgroups: sci.military
Subject: Re: Spoofing GPS signals?
Message-ID: <6150@cbnews.ATT.COM>
Date: 2 May 89 03:29:45 GMT
References: <5984@cbnews.ATT.COM>
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From: henry@zoo.toronto.edu (Henry Spencer)
>[Accuracy] depends on how long you watch, how many "birds" you can see,
>your a priori, and the quality of your sattelite emphermis. NASA/JPL
>routinely uses the civilan signals to obtain millimeter accuracies.

One reason for this is that the current birds are "pre-production" versions.
The "production" ones, now starting to be launched, include some sort of
capability whereby DoD can degrade the accuracy of the unencrypted signal
whenever they feel like it.  Potential users in fields like aviation do
*not* like this, especially since there is no provision for warning of it.

                                     Henry Spencer at U of Toronto Zoology
                                 uunet!attcan!utzoo!henry henry@zoo.toronto.edu