IRAF Help page for: HGREMAP
HGREMAP (April98) grasp.pipeline HGREMAP (April98)
NAME
hgremap -- Transfer GONG images to heliographic coordinates
USAGE
hgremap input
PARAMETERS
input
List of input solar disk images.
trim_file = "pipeline$lib/plm250.sinlat"
PLMTRIM's output ASCII triming file.
offset = 90.
Camera offset angle (degrees) measured eastward from north.
pangle_cor = no
Perform correction for solar P-angle when remapping to
heliographic coordinates? Used for GONG prototype and field
data when the camera rotator is off.
coude_cor = no
Perform correction for Coude rotation of the images when
remapping to heliographic coordinates. Used for GONG
Breadboard instrument data.
turret_cor = no
Perform correction for turret rotation of the images when
remapping to heliographic coordinates. Used for GONG prototype
and field data when the camera rotator is off.
interp_type="spline3"
Type of image interpolator to be used when remapping to
heliographic coordinates. The minimum match abbreviated
choices are:
"nearest"
Nearest neighbor interpolation.
"linear"
Linear interpolation.
"poly3"
Third order divided differences.
"poly5"
Fifth order divided differences.
"spline3"
Cubic spline interpolation.
"sinc"
Sinc function interpolation.
geometry = "fndlmb"
Geometry type.
"fndlmb"
Use results of gongcor.fndlmb for image center and radii.
"hgeom"
Use results of Toner's Hankel geometry code for image
center and radii.
NOTE: this option will disappear once the Hankel geometry is
included as a standard part of the upstream reductions.
apod_type = "cos"
Apodization type.
"none"
No apodization performed.
"cos"
Cosine apodization (i.e., equal area) function.
"kb"
Kaiser-Bessel apodization function.
"dc"
Dolph-Chebychev apodization function.
"cb"
Cosine-Bell (or Tuckey) apodization function.
apod_par = 2.5
Value of parameter alpha for Kaiser-Bessel or Dolph-Chebychev
apodization functions.
apod_cbr = 0.75
Apodization radius for Cosine-Bell apodization function.
orientation = "counter"
Input image orientation.
"counter"
Heliographic west is counterclockwise to heliographic
North. This is the orientation of the GONG.
"clock"
Heliographic west is clockwise to heliographic North.
mask = no
Apply moving mask
mask_cbr = 0.01
Moving mask radius for cosine-bell apodization.
mask_EWrad= 0.99
Maximum mask fractional radius in the E-W direction.
mask_NSrad = 0.98
Maximum mask fractional radius in the N-S direction.
DESCRIPTION
HGREMAP transfers GONG input images into heliographic coordinates. Remapped
images may be apodized and a moving mask may be applied. Although the input is
assumed to be GONG data, other data sets may be reduced provided
the proper header keywords and values are placed in the input
images.
HGREMAP expects to find the following input image header keywords:
KEYWORD DATA TYPE DESCRIPTION
DATE-OBS string UT date of observation (YYYY/MM/DD)
TIME-OBS string UT time of observation (HH:MM:SS.SSSS)
SITE string 2-character site abbreviation (e.g., TC)
LAT real Latitude of observing site (degrees)
FNDLMBXC real X-center of images (pixels)
FNDLMBYC real Y-center of images (pixels)
FNDLMBMA real Radius of semi-major axis (pixels)
FNDLMBMI real Radius of semi-minor axis (pixels)
FNDLMBAN real Ellipse rotation angle (degrees)
counter clockwise from Y-axis
C_MA real Radius of semi-major axis (pixels) from
Hankel geometry (optional)
C_MI real Radius of semi-major axis (pixels) from
Hankel geometry (optional)
FILLED bool Image is a fill image not to be used in
processing
The trim_file is a file produced by grasp.suntrans.plm_trim, and
contains information about the size of the heliographic remapping
grid, the type of grid (equally spaced in sin(latitude) or
latitude), the maximum L-value for the spherical harmonic transform
(SHT), the SHT type (all-m or even-m) and other information
required by the SHT subroutine. For standard GONG reductions:
Lmax = 250
SHT_TYPE = all-m
number of heliographic longitude points = 372
number of heliographic latitude points = 220
latitude grid is equally spaced in sin(latitude)
If apod_type != none, then an apodization image is created by
making an aritificial disk image of unit value, apodizing it,
remapping to heliographic coordinates and normalizing it to unit
power. The remapped image is saved in memory. The apodization
windows are given by:
apod_type = cos
Cosine (or equal area) apodiztion.
apod(x,y) = cos[sqrt(1 - x**2 - y**2)]
The response of this apodization function has a narrow core
and high first sidelobe.
apod_type = dc
Dolph-Chebychev apodization with alpha = apod_par.
apod(x,y) = DFT(x,y)[W(k)]; DFT = Discrete Fourier Transform
where
cos[ arcos[ beta cos[PI*k/N]]]
W(k) = -1**k * ------------------------------
cosh[ N * arcosh(beta)]
beta = cosh[(1/N) * arcosh(10 ** alpha)]
The parameter alpha represents the log of the ratio of
main-lobe to sidelobe level. As alpha increases, the width
of main-lobe increases. The sidelobes are of equal height.
apod_type = kb
Kaiser-Bessel apodiztion with alpha = apod_par.
I0(PI*alpha*rho)
apod(x,y) = ----------------
I0(PI*alpha)
where
I0 == Modified Bessel Function for n=0.
The response of this apodization has a wider core, but
smaller sidelobes than the Dolph-Chebychev function.
apod_type = cb
Cosine-Bell (Tukey) apodization, with apodization radius ,
Rcb=apod_cbr. If the radius of the disk is R, then
/ 1.0 0 <= r/R <= Rcb
/
apod(x,y) = <
\ PI [(r/R)-Rcb]
\ 0.5*[1. + cos --------------; Rcb <= r/R <= 1.0
2 (1 - Rcb)
The response of this function has a very narrow core, but
also very high and ugly sidelobes.
Each image is that is processed is remapped into heliographic
coordinates according to the specifications in the \Itrim_file\R.
If pangle_cor=yes, the solar P-angle is calculated by an
ephemeris subroutine and taken into account during the
remapping. This correction is required when reducing GONG
Breadboard data, Taiwan Network data, or GONG prototype and
field data taken with the camera rotator off.
If coude_cor=yes, a Coude angle is calculated by an ephemeris
subroutine and taken into account during the remapping. This
correction is required when reducing GONG breadboard data.
If turret_cor=yes, a Turret angle is calculated and taken into
account during the remapping. This correction is required for
GONG prototype and field data when the camera rotator is off.
If geometry=fndlmb, DNSPIPE will look for the major and minor
axis lengths from the keywords FNDLMBMA and FNDLMBMI.
If geometry=hgeom, DNSPIPE will look for the major and minor
axis lengths from the keywords C_MA and C_MI.
If orientation=counter, the remapping is done assuming that
heliographic west is on the counterclockwise side of
heliographic north for the input images. This is the normal
orientation of the GONG images.
If orientation=clock, the remapping is done assuming that
heliographic west in on the clockwise side of heliographic
north for the input images. This is the normal orientation of
the South Pole Experiment data.
EXAMPLES
1. To remap list of GONG magnetograms to heliographic coordinates. Using the
standard reduction defaults.
pi> files *mag*.fits > maglist
pi> hgremap @maglist
TIME REQUIREMENTS
BUGS
If using the fits kernal, all images must have the pixtype of real or HGREMAP appends
characters to the output image names. To correct for this problem use:
pi> chpixtype *fits *fits "r"
Data
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