University of Miami GPS Volcano Monitoring Data on Surface Deformation: Available via Internet

University of Miami GPS volcano monitoring data on
surface deformation: available via Internet

GPS volcano monitoring data is available from the University of Miami
ftp site:

corsica.rsmas.miami.edu in directory /pub

Additional information about data holdings, related research and
relevant imagery and data are made available at the following URL:

"http://www.geodesy.miami.edu/"

The following information about the data sets was abstracted from the
README file located in the /pub directory of the FTP site:

This directory contains "quick-look" GPS results for the permanent
station CASA at Mammoth Lakes, California, located near the top of the
resurgent dome at the USGS 2 color laser facility. The data begin
April 20, 1994. Results were obtained with the GIPSY software
developed at JPL. We give absolute as well as relative positions for
3 sites: CASA, Goldstone (id. GOLD) and Quincy (id. QUIN). The
reference frame is ITRF92. Distances are given in meters, latitude and
longitude in degrees, but all formal errors are in meters.

Directory Content :

- CASA.XYZ, GOLD.XYZ, QUIN.XYZ : X, Y, Z Coordinates and their errors.

- CASA.GC : Geocentric Coordinates, Longitude, Latitude, Radial Height (from
the earth's center of mass) and their errors.

- QUINCASA.NEV, GOLDCASA.NEV : Relative baseline components (north, east,
vertical) of the second site with respect to the first site,
plus corresponding errors and their correlations. The first entry
after the "+-" is the error; entries to the right of the error are
the correlations.

- STATION.DIFF : Differences between daily results and official ITRF92
coordinates for selected sites mapped to epoch.
This gives an indication of the accuracy of the results.

Strategy used in the analysis :

- The zenith wet troposphere delay is estimated every 6 minutes and
modelled as a random walk stochastic process (Dixon et al., 1991).

- Carrier phase cycle ambiguities (biases) are estimated, not fixed.

- No fiducial (fixed) sites are used in the analysis.
Rather, results are transformed into the ITRF92 reference frame using
6 to 10 collocated sites, following the approach of Heflin et al.
(1992) and Blewitt et al. (1992).

- Prior to June 1, 1994, IGS precise orbits were used, and 12-15
stations were analyzed daily.

- Beginning June 1, 1994, data editing was improved, and an average of
20 stations were included in the analysis; we continued to use IGS
precise orbits until June 30, 1994.

- Beginning July 1, 1994, satellite orbits are estimated
simultaneously with station positions to facilitate production of
near real-time results, and the number of stations included in the
daily analysis increased to an average of 25.

- Prior to January 31, 1995, only phase data are used (no P-code) due
to Anti-Spoofing (A/S). We began to use P-code from Feb. 1, 1995, and
changed to use P-code observations just from some sites with good
quality on Feb. 24, 1995.

- On Feb. 1, 1995 the elevation cutoff angle of observations changed
from 20 degrees to 15 degrees.

- From March 3, 1995, corrections of antenna phase center variations
are included in our analysis.