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Path: utzoo!linus!philabs!seismo!flinn
From: flinn@seismo.UUCP (E. A. Flinn)
Newsgroups: net.space
Subject: re: G.K. O'Neill's satellite plan
Message-ID: <567@seismo.UUCP>
Date: Sun, 29-Jan-84 11:19:44 EST
Article-I.D.: seismo.567
Posted: Sun Jan 29 11:19:44 1984
Date-Received: Tue, 31-Jan-84 02:03:13 EST
References: <16109@sri-arpa.UUCP>
Organization: Center for Seismic Studies, Arlington, VA
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	Two potentially important uses for GPS are in civil surveying and
in geophysical research.  Texas Instruments and a small company in
Massachusetts have developed and are already beginning to market 
backpack units which can determine position to a few centimeters in a 
geocentric coordinate system (i.e., the coordinate system defined by 
the GPS satellite orbits), although they do not work in real time.  
These units are not much more expensive than the usual doppler 
geoceiver rigs, which are accurate to a meter or so.  NASA is also
developing small GPS receivers for two purposes: (1) to locate
altimeter satellites to a few centimeters (the altimeters have 2-cm
accuracy and require similar knowledge of orbital position), and to
monitor crustal deformation and movement of the tectonic plates.  The
NASA and competing units are now being field-tested in California, and
there should be papers given at the next meeting of the American
Geophysical Union on the results of this comparison study.

	For further information on geophysical applications of this
kind of space technology, see an article I wrote for Science in June
1981, and the references cited there.