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--></style><title>Reprocessed IGS Trop Product now available with
Gradients</title></head><body>
<div>Authors: Yoaz Bar-Sever and Sung Byun</div>
<div><font face="Arial"><br></font></div>
<div><font face="Arial"><br></font></div>
<div>Dear Colleagues:<br>
</div>
<div>We'd like to announce the availability the reprocessed IGS
tropospheric product. The reprocessed product is based on IGS
reprocessed orbit and clock from 1995 to 2007.</div>
<div><br></div>
<div>The reprocessed product, and all products going forward from 2007
now include estimates of the North and East delay gradients, in
addition to the zenith path delay.</div>
<div><br></div>
<div>The only other change to the estimation approach was the
replacement of the Niell mapping function with GMF. A summary of the
estimation approach is provided below.</div>
<div><br></div>
<div>While retaining the naming convention of the trop product files,
the format has been expanded slightly to accommodate the addition of
gradients, hopefully in a transparent manner:</div>
<div><br></div>
<div>The "SOLUTION_FIELDS_1" line of the Header now specify
the gradient fields. For example:</div>
<div><br>
+TROP/DESCRIPTION<br>
*KEYWORD______________________ VALUE(S)______________<br>
SAMPLING
INTERVAL <span
></span
> <span
></span>
300<br>
SAMPLING
TROP <span
></span
> <span
></span
> <span
></span> 300<br>
ELEVATION CUTOFF
ANGLE <span
></span
> <span
></span> 7.0<br>
TROP MAPPING FUNCTION
GMF</div>
<div
> SOLUTION_FIELDS_1 <span
></span> TROTOT STDDEV N_GRAD STDEV
E_GRAD STDEV<br>
-TROP/DESCRIPTION<br>
<br>
<br>
The main body of the file which contains data now looks as follows
(eg, for ALGO site on 2010-123):<br>
<br>
+TROP/SOLUTION<br>
*SITE EPOCH_______ TROTOT STDEV N_GRAD STDEV E_GRAD
STDEV<br>
ALGO 10:123:00000 2421.4 1.9 -4.634
3.733 -0.861 2.125<br>
ALGO 10:123:00300 2421.3 1.9 -4.614
3.692 -0.883 2.106<br>
ALGO 10:123:00600 2421.5 1.8 -4.541
3.617 -0.793 2.091<br>
ALGO 10:123:00900 2421.8 1.7 -4.490
3.539 -0.527 2.069<br>
ALGO 10:123:01200 2421.9 1.7 -4.508
3.456 -0.397 2.035<br>
<br>
Note that all units are in mm. These files are available at both JPL
and CDDIS sites.<br>
<br>
At JPL:</div>
<div>ftp://sideshow.jpl.nasa.gov/pub/igs_trop/trop_zpd/repro1/yxxxx
(from 1995 to 2007)</div>
<div>ftp://sideshow.jpl.nasa.gov/pub/igs_trop/trop_zpd/yxxxx (from
2008 to present)</div>
<div><br>
At CDDIS:</div>
<div
>ftp://cddis.gsfc.nasa.gov/pub/gps/products/troposphere/zpd/repro1/xx<span
></span>xx (from 1995 to 2007)</div>
<div
>ftp://cddis.gsfc.nasa.gov/pub/gps/products/troposphere/zpd/xxxx <span
></span
>
(from 2008 to present)</div>
<div><br></div>
<div>With this reprocessing we now have 15 years of consistently
derived trop products from hundreds of sites.</div>
<div><br></div>
<div><b>Summary of estimation approach:</b></div>
<ul>
<li>Fixed orbits and clocks: IGS Final Re-Analyzed Combined
(1995-2007), and IGS Final Combined 2008-Current
<li>Earth orientation: IGS Final Re-Analyzed Combined (1995-2007), and
IGS Final Combined (2008-Current)
<li>Transmit antenna phase center map: IGS Standards
<li>Receiver antenna phase center map: IGS Standards
<li>Elevation angle cutoff: 7 degrees
<li>Mapping function (hydrostatic and wet):<font color="#3900FC">
GMF</font>
<li>A priori delay (m): hyd = 1.013*2.27*e -0.116*ht wet = 0.1
<li>Data arc: 24 hours
<li>Data rate : 5 minutes
<li>Estimated parameters: station clock (white noise), station
position, wet zenith
<li>delay (3 cm/hour random walk), delay gradients (0.3 cm/hour
random walk), phase biases (white noise)</ul>
<div><br></div>
<div>Contact Sung Byun <<a
href="mailto:byun@jpl.nasa.gov">byun@jpl.nasa.gov</a>> or Yoaz
Bar-Sever <<a
href="mailto:Yoaz.E.Bar-Sever@jpl.nasa.gov"
>Yoaz.E.Bar-Sever@jpl.nasa.gov</a>> with any question</div>
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