GVCALC(1)
NAME
gvcalc - calculation of velocity from sets of MDI filter-
grams taken through a heliostat
SYNOPSIS
gvcalc [-qvrf] [argument= value ...]
DESCRIPTION
gvcalc calculates Dopplergrams from sets of MDI filtergrams
taken through the heliostat ground testing system. The fil-
tergrams are assumed presnt in groups of five at tuning
positions 0 through 4 (nominal continuum, -120 mA, -40 mA,
+40 mA, +120 mA from filter transmission center, respec-
tively). The location of the image center is found for the
individual filtergrams using the limb finder fit_limb() and
the average and rms center is saved. The images are not
registered prior to the doppler shift calculation. The
Doppler velocity is computed using the mdi_vcalc() function.
The resulting image is inverted unless the no-flip flag (-f)
is given. The position angle is computed based on the
observation time and date but the Dopplergram is not
rotated. The determined radius is used to differentiate
full disk from calmode and high-res images. If the image is
determined to be a full disk measurement a calibration
Doppler image is subtracted. If the raw flag (-r) is given,
the calibration image is not subtracted and the ephemeris
corrections (subtraction of Earth's spin and orbital motion)
are not made.
The -q option prints out the list of required arguments and
their default or environmental values, then quits. The -v
option sets verbose mode, redirecting history from stdout to
stderr.
OPTIONS
in0=name dataset of filtergrams at tuning posi-
tion 0 (no default)
in1=name dataset of filtergrams at tuning posi-
tion 1 (no default)
in2=name dataset of filtergrams at tuning posi-
tion 2 (no default)
in3=name dataset of filtergrams at tuning posi-
tion 3 (no default)
in4=name dataset of filtergrams at tuning posi-
tion 4 (no default)
outlog=name name of log file (default:
/home/soi/data/logs/V_mdi.log)
out=name output dataset (default: Vobs.fits)
calib=name calibration dataset (default:
/home/soi/calib/calib.256.fits)
vtable=name velocity lookup table (default:
/home/soi/tables/VTable.fits)
frac_lenside=Real parameter for limb finding (default:
70/1024)
frac_box=Real parameter for limb finding (default:
200/1024)
frac_thresh=Real parameter for limb finding (default:
0.3)
KEYWORDS
The following keywords are set in the output file:
GVCALC_VERS Current gvcalc version.
VTABLE_VERS VTable used in Doppler velocity calcula-
tion.
VRES Velocity resolution in m/s.
ISFLIPT Boolean true if image flipped top to
bottom.
X0 Location of image center in pixels.
Y0 Location of image center in pixels.
X0_RMS Standard deviation of image center
determination.
Y0_RMS Standard deviation of image center
determination.
RMAJOR Determined image radius in pixels.
R_RMS Standard deviation of image radius.
P P-angle to rotate image CW for N at top,
E to left.
B0 Latitude of sub-earth point.
V_ORBIT Line-of-sight velocity of MDI.
IMAGE_T Time of image observation.
MDI_PATH FullDisk or HighRes indicator.
MDI_DATA Observable indicator == "Doppler".
CALIBFN Calibration file path.
VTABLE_NAME Velocity lookup table filename.
LOGFN Log file name.
MDI_MODE Image or cal mode indicator, "Image" or
"Calib".
EXAMPLES
FILES
/home/soi/tables/VTable.fits
SEE ALSO
fit_limb(3), mdi_vcalc(3)
DIAGNOSTICS
BUGS
It would be a lot more convenient to have the associated
filtergrams collected in a single dataset.
The parameters used by the limb finder should not have to be
set as arguments.
Standard library IO functions are used to create output log.
The name of the output log file should be determined from
the input data; without a default.
The calib image to be subtracted is only correct for 256x256
images.
There is no correct recognition of High-Res images.
AUTHORS
Phil Scherrer, Rick Bogart, Kay Leibrand, Luiz Sa, Katie
Scott
HISTORY
1994-02-14 SOI Version 0.8