; APGPS
;---------------------------------------------------------------
;! Apply GPS-derived ionospheric corrections
;# Task Calibration VLA
;-----------------------------------------------------------------------
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;; Associated Universities, Inc. Washington DC, USA.
;;
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;-----------------------------------------------------------------------
;---------------------------------------------------------------
APGPS LLLLLLLLLLLLUUUUUUUUUUUU CCCCCCCCCCCCCCCCCCCCCCCCCCCCC
APGPS Task to apply ionospheric delay and Faraday rotation
corrections derived from GPS measurements
INNAME Input UV file name (name)
INCLASS Input UV file name (class)
INSEQ 0.0 9999.0 Input UV file name (seq. #)
INDISK 0.0 9.0 Input UV file disk unit #
ANTENNAS Antennas to correct
SUBARRAY 0.0 9999.0 Subarray to correct
0 -> all
OPCODE Corrections to apply
'IFR ' - Faraday rotation
only
'DISP' - dispersive delay
and Faraday rotn
default: IFR only
INVERS Version number of GP table
containing GPS data
GAINVER Input CL table version
GAINUSE Output CL table version
PRTLEV Print level
0 -> none
1 -> solutions
2 -> more detail
----------------------------------------------------------------
APGPS
Task: Uses GPS delay data stored in a GP table to calculate
phase corrections due to the excess path length of
the ionosphere and to calculate the ionospheric Faraday
rotation.
Adverbs
INNAME.....Input UV file name (name). Standard defaults.
INCLASS....Input UV file name (class). Standard defaults.
INSEQ......Input UV file name (seq. #). 0 => highest.
INDISK.....Disk drive # of input UV file. 0 => any.
ANTENNAS...List of antenna numbers to correct. If all of the
entries are zero then ionospheric corrections will
be generated for all antennas. If any of the
entries are not blank then corrections will only be
generated for those antennas with numbers listed in
this array unless at least one entry is negative
when corrections will be generated for all antennas
except those whose numbers correspond to the
absolute values of the non-zero entries.
SUBARRAY...Subarray to correct. Corrections will only be
generated for the subarray with this number unless
this number is zero, in which case all antennas
matching the ANTENNAS selection will be corrected
in all subarrays.
OPCODE.....Type of corrections to generate. If this is 'DISP'
then both dispersive delay and ionospheric
Faraday rotation corrections will be generated
otherwise only ionospheric Faraday corrections
will be generated.
INVERS.....Version number of GP table. 0 => highest
GAINVER....Version number of CL table to use. 0 => highest
(used to define times at which corrections are
calculated)
GAINUSE....Version number of output CL table. 0 => new
PRTLEV.....Print level
0 => no printout (default)
1 => model TEC, gradients in latitude and
longitude and residual sum of squares
----------------------------------------------------------------
APGPS: Calculate ionospheric Faraday rotation and delay from
GPS data
Documentor: Chris Flatters
Related Programs: LDGPS
APGPS fits a simple model of the total electron content of the
ionosphere to GPS delay data and uses this model to calculate
corrections for the ionospheric Faraday rotation and delay.
The model is parameterized by the total electron content at the
zenith above the GPS receiver and linear gradiants in latitude
and longitude. This isa reasonable model only for reasonably
compact arrays situated close to a GPS receiver.
If you use APGPS for arrays more than a few kilometers in size,
you should use ANTENNAS to make sure that corrections are only
applied to antennas close to the receiver. If you have data from
more than one receiver then you can run APGPS for each receiver,
selecting a different set of antennas for each run.
This program is primarily intended to correct VLA data using
data from GPS receivers at the VLA site.
PRINTOUT
If PRTLEV is set to 1 or a greater value then APGPS will
print out
- the model TEC at the zenith,
- the TEC gradients in latitude and longitude,
- the residual sum of the squares, and
- the fractional error bound
every time it recalculates the ionospheric model. If the
true ionospheric model is characterized by a vector x
(with x(1) = TEC, x(2) = gradient in longitude, x(3) = gradient
in latitude) and the model calculated by APGPS is x' then
the fractional error that is printed is an upper bound on
|| x - x' || / || x ||
where || x || denotes the L2 norm (or the sum of the squares)
of x.
The residual sum of the squares and the error bound may help
in finding poor solutions.
If PRTLEV is set to 2 or more then APGPS will also print out
the model zenith TEC for each satellite that provided data in
the solution interval (identified by PRN) and the mean and
standard deviations of the measured zenith TECs.