[IGSMAIL-0662] New ERP Format
AC
AC
Thu Jul 7 11:56:00 PDT 1994
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IGS Electronic Mail Thu Jul 7 11:56:00 PDT 1994 Message Number 0662
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Author: AC Coordinator
Subject: New ERP Format
Dear colleagues,
For your information, included bellow is a description of the the new IGS
standard erp format which is being adopted by all AC starting with the GPS week
756 (July 3/94) reports. This version is a result of discussions amongst all
AC and IERS and hopefully will allow improved EOP resolutions, flexibility and
improved orbit combination.
With many greetings
Jan Kouba
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Near-term earth orientation format proposal:
--------------------------------------------
field contents/HEADER comment
========================================================================
mandatory (i.e, all fields 1-10 must be coded should follow the order
bellow and separated by at least one blank):
1 MJD modified Julian day, with 0.01-day precision
2 Xpole 10**-5 arcsec, 0.00001-arcsec precision
3 Ypole 10**-5 arcsec, 0.00001-arcsec precision
4 UT1-UTC, UT1R-UTC
UT1-TAI, UT1R-TAI 10**-6 sec, 0.000001-sec precision (usec)
5 LOD, LODR 10**-6 ms/day 0.001-ms/day precision (us/day)
6 Xsig 10**-5 arcsec, 0.00001-arcsec precision
7 Ysig 10**-5 arcsec, 0.00001-arcsec precision
8 UTsig 10**-6 sec, 0.000001-sec precision (usec)
9 LODsig 10**-6 sec/day, 0.001-ms/day " (us/day)
10 Nr number of receivers in the solution (integer)
11 Nf number of receivers with "fixed" coordinates
12 Nt number of satellites (transmitters) in the solution
(integer)
optional (field 11->, only some may be coded, the order is also optional):
13 Xrt 10**-5 arcsec/day 0.01-mas/day precision
14 Yrt 10**-5 arcsec/day 0.01-mas/day precision
15 Xrtsig 10**-5 arcsec/day 0.01-mas/day "
16 Yrtsig 10**-5 arcsec/day 0.01-mas/day "
17 XYCorr X-Y Correlation 0.01 precision
18 XUTCor X-UT1 Correlation 0.01 "
19 YUTCor Y-UT1 Correlation 0.01 "
20 -> other parameters e.g. DPsi, DEpsi, their sigmas DPsig, DEsig, etc.
Should be described in the files (what they are, units, etc.)
------------------------------------------------------------------------
The .erp file can be form in the following way:
-------------
Before :any optional text/lines. The EOP table starts and is recognized by the
header, i.e. the character string, " MJD "
(the first, optional text line can be used e.g. for software/estimation
strategy/ITRF version identification/testing)
EOP Table:
line 1: Column heading starting with " MJD " (exact headings for f. 1-10)
line 2: units (in particular for yet undefined fields 20->)
line 3: values: SEPARATED BY AT LEAST ONE BLANK, leading 0's optional
line 3: " "
.
.
last line: a blank line (optional, only needed if any optional text bellow
is coded, otherwise EOF will terminate the values and the file.
After : Any (optional) text
-------------
REMARKS:
-For field numbers 4, 5 UT1-UTC and LOD are recommended. UT1R-UTC, UT1-TAI,
UT1R-TAI and LODR are acceptable alternatives. The heading should
reflect which of these is used.
- It is strongly recommended that AC reconstruct the UT1(R)-UTC (UT1(R)-TAI)
exactly to correspond to the submitted orbits.Such UT series may be assigned
corresponding sigmas, otherwise zero sigmas should be used to indicate fixed
values or values not to be used in any EOP combination solutions.
- the rates may be based on solution/apriori EOP. Non zero sigmas will
indicate solutions and zero (or omitted) sigmas indicate nominal (apriori)
rates.
- note that by using rates, the EOP discontinuities (e.g. as is the case for
midnight UT for most AC) can also be modelled without having different EOP
values at the same (UT midnight).
- the first 12 fields are widely used now and the optional part (field
13-16) should not affect most users, yet it contains all the necessary
resolution for precise reconstruction of orbit transformation from
terrestrial to inertial coordinate frames at the sub-cm level.
EXAMPLE (two line header):
(In this example, since the apriori EOP rates are given, no rate sigmas are
included. Alternatively zero rate sigmas could have been used. The example
reconstructs EMR EOP solutions completely, including the EOP discontinuities
at UT midnights. Note, this is equivalent to giving three EOP values daily,
i.e. at 0h, 12h and 24h as the given rates are only valid from 0 to 24h
UT. on each day)
MJD Xpole Ypole UT1-UTC LOD Xsig Ysig UTsig LODsig Nr Nf Nt Xrt Yrt
10**-5" 10**-5" usec us/d 10**-5" us us/d 10**-5/d
49466.50 18315 34988 -80220 2912 18 21 50 0 20 12 25 50 -224
49467.50 18341 34787 -83260 2746 18 20 60 0 21 12 25 47 -225
49468.50 18274 34565 -86180 2549 18 21 60 0 20 12 25 44 -225
49469.50 18284 34280 -88870 2375 18 19 60 0 20 13 24 39 -259
49470.50 18283 33971 -91410 2266 18 21 60 0 20 13 25 34 -294
49471.50 18360 33719 -93900 2231 20 22 70 0 20 13 25 32 -277
49472.50 18414 33480 -96360 2256 16 19 70 0 21 13 25 36 -213
---End of example------------
[Mailed From: Jan Kouba <kouba at geod.emr.ca>]
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