Subject: [SCIGN-0381] USGS Analysis Subject
From: Jeff Behr
Date: 3 Apr 1998 11:25:49

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SCIGN Electronic Mail    Fri Apr  3 11:25:49 PST 1998      Message Number 0381
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Author: Jeff Behr
Subject: USGS Analysis

Subject: USGS Processing on the Web

April 3, 1998

The USGS-Pasadena announces daily updates of station positions 
for 47 SCIGN stations processed to support the SCIGN earthquake 
response capability.  USGS processing uses the GAMIT/GLOBK soft-
ware and the IGS predicted ephemeris for rapid update of station 
positions.  Processing typically completes by 1:30 PM PT (21:30 
UTC) with graphics of station position posted to the USGS Web 
pages at:

	http://www-socal.wr.usgs.gov/scign/Analysis

Daily analyses from June 1997 to March 1998 produced coordinate 
estimates dominated by inaccuracies in the predicted orbits.  Day-
to-day scatter in station positions were on the order of 26-34 mm
horizontal, 32-38 mm vertical.  Introduction of the GLOBK module 
GLORG to redefine the reference frame (ITRF 96) on the basis of 
well-known SCIGN station coordinates and velocities minimized the 
region-wide error, leading to typical day-to-day scatter of approx-
imately 3-6 mm horizontal, 8-18 mm vertical.

We'd like to thank Tom Herring, Bob King and Simon McClusky for 
their support of the USGS processing.  We'd also like to thank the 
IGS analysis centers for providing predicted orbits for such 
applications.

We welcome comments on our analysis technique, our results and
our presentation.  Please send them to [email-masked].

Thanks, 
Jeff Behr  

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Jeff Behr
SCIGN Operations Center                 TEL: (626) 583-7816
US Geological Survey                    FAX: (626) 583-7827
525 S. Wilson Ave.
Pasadena, CA 91106                      [email-masked]
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[Mailed From: Jeff Behr <[email-masked]>]