FASTRACK(1)
NAME
fastrack - strategy module to create one or more time series
of maps of regions tracked in heliographic coordinates
extracted from a series of solar images
SYNOPSIS
fastrack [-clnvz] [argument= value ...]
DESCRIPTION
fastrack extracts from a series of solar images multiple
regions fixed in co-moving frames at a set of initially
specified heliographic coordinates. The tracked regions are
of a common specified size, and the same map projection is
used, only the central point varying. Depending on the
nature of the tracking, the heliographic coordinates of the
map centers will be continuously adjusted as functions of
time, matching the specified coordinates only at the start.
If a tracking matching the Carrington rate is selected, the
heliographic coordinates of all map locations will, by
definition, remain fixed.
If images are missing from the input data series or other-
wise rejected, fastrack will linearly interpolate in time
across the gaps in the mapped output. (Missing images at
the end points result in continuation backward or forward
from the first or last valid map.) Partial input images may
produce missing values in the mapped images.
The input data series is normally assumned to be continuous,
so if an image selection range is made (...,series:XXX[I-
J],sel:[M-N]) the first selector (M)is assumed to apply only
to the first data set (I) and the last selector (N)to apply
only to the last data set (J); all intervening images are
accepted. The -c flag forces the image selection to apply
independently to each data set in the series.
The -l flag sets a "lagrangian" tracking option, forcing the
tracking to be at the differential rotation appropriate to
the instantaneous latitude for each point in the region,
rather than at a common rate for the whole region.
The -n option "turns off" tracking in the sense that the
images are tracked at minus the Carrington rate. There is
no correction for observer motion in the latitudinal direc-
tion, so this is not quite the same as mapping to fixed
heliocentric coordinates.
The -z flag directs the output maps to be organized in polar
coordinates, with azimuthal angle the most rapidly varying
coordinate, (columns) and radial distance from the map
center the next (rows). The length of the angle dimension
in that case will not be a power of 2 unless set by the cols
value.
If the verbose option (-v) is set, one line of history
information will be produced per input image.
The mapped data sets are placed in one or more 3-dimensional
FITS files, with time (image serial number) the most slowly
varying axis.
ARGUMENTS
in=Dataset
The input dataset name. The input dataset is expected
to be a series of calibrated images of all or part of
the solar disc in a "plate" coordinate system. The
dataset is assumed to include in its ancillary data the
parameters required for heliographic mapping, namely
the observation time and heliographic location. NO
DEFAULT
out=Dataset
The output dataset name. NO DEFAULT
bckgn=name The file name of a background image to
be subtracted from the data for purposes
of detrending. If not supplied, no
detrending is performed. Note that the
background image must be in the same
format as the images. If it is used,
all images in the input data set must be
in or reconstructable to the same for-
mat; detrending is performed before the
images are mapped. If the background
image is 1-dimensional (presumably
corresponding to MDI crop format),
detrending will be performed before the
images are reconstructed.
lat=real The array of heliographic latitudes (in
degrees) of the centers of regions at
start of tracking. (Default [0.0])
lon=real The array of heliographic longitudes (in
degrees) of the centers of regions at
start of tracking. (Default [0.0])
Note: if multiple latitudes and longi-
tudes are requested, the number should
agree; if it doesn't, the longer array
is used and the unspecified latitude or
longitude center values default to the
last one specified.
map=string Mapping projection option: recognized
values are "rectangular", "Postels",
"gnomonic", "stereographic", "ortho-
graphic", "Lambert", "cyleqa", "sineqa",
and "Mercator". (Default: "Postels")
scale=real Scale of maps (in heliographic degrees /
pixel) at a location appropriate for the
selected mapping option; a 0 value
implies autoscaling to best scale of
image. Typical values would be about
0.057 * resolution [arcsec / pixel] for
solar radii of 1000 arcsec, or about
0.12 for SOI full-disc images (or HiDHN
or HLH or TON images). Default: 0.0,
implying auto-scaling.
map_pa=real Position angle of the north direction on
the output image, measured positive
counterclockwise, in degrees. (Default:
0.0)
radius=real The desired minimum radius of all
tracked regions, in heliographic
degrees. This is advisory only; if
used, the maps will be squares of length
equal to the smallest power of two at
the chosen map scale necessary to
include the minimum radius, unless
over-ridden by the rows and cols argu-
ments (see below). For a typical scale
of 0.12, a radius of about 15 deg
corresponds to a 128*128 map. If both
rows and cols are non-zero, this argu-
ment is ignored.
cols=int
rows=int The desired number of columns (rows) in
the mapped images; if non-zero, each
over-rides the corresponding auto-scaled
dimension appropriate to the radius
paremeter. (Default: 0)
a0=real
a2=real
a4=real a0, a2, and a4 are the coefficients in a
sin^2 (latitude) expansion of the dif-
ferential rotation rate, minus the Car-
rington rotation, in microradian / sec.
Thus, if they are all 0, rigid
Carrington rotation is assumed. The
default values, a0 = -0.02893, a2 =
-0.3441, a4 = -0.5037, correspond to the
Mt Wilson 1982/84 differential rotation
rate determined by Snodgrass. Ignored
if the -n flag is set.
merid_v=real Meridional velocity to be used for
tracking, in microradian / sec, positive
northward. (Any anomalous zonal velo-
city must be included in a0.) Ignored
if the -n flag is set. (Default: 0.0)
xc=float (Defaults 0.0)
yc=float If non-zero, specify the coordinates of
the solar disc center of each image,
overriding whatever the appropriate data
keywords provide. The locations are
assumed to be specified in units of
image pixels measured from (0, 0) at the
center of the first image pixel.
imgscale=real The plate scale to be assumed for each
image, in arcsec / pixel. If specified,
this value overrides that found in the
input data. (Default: Not specified)
basename=name If the basename is "lat", the output
maps will be named latBB.BN.fits or
latBB.BS.fits or lat00.0.fits, where
BB.B is the specified central latitude
of the map. If the basename is "lon",
the output maps will be named
lonLLL.L.fits, where LLL.L is the cen-
tral longitude (at start of tracking, of
course). If the basename is "latlon",
the output map names will combine the
above forms, e.g.
latBB.BNlonLLL.L.fits. Otherwise, the
files will be named NNNN.fits, where
NNNN is the map number. (Default: Not
specified)
EXAMPLES
fastrack -pad in=
prog:mdi,level:lev1.4,series:fd_V_01h[29818-29843],sel:[7-
42] out=
prog:mdi,level:lev2_track,series:vtrack_07_015_01536[45836]
cols= 128 rows= 128 scale= 0.125 lat= {-30.0,-
15.0,0.0,15.0,30.0} lon= 60.0 basename= lat
FILES
SEE ALSO
track_region(1), project(1)
DIAGNOSTICS
soi_errno is returned and also set as the abortflg value in
the results keylist.
BUGS
The "lagrangian" tracking option is untested and probably
very slow. Because it calculates the instantaneous longi-
tude for each point from an integrated rotation rate based
on its current latitude, the use of this option with a non-
zero meridional anomalous velocity is likely to produce
results that are at best difficult to interpret.
Whether or not a mapped point is on the visible hemisphere
(within 180 degrees of requested tracking center) is deter-
mined once for all at the outset; if the proper motion is
very large and the tracking time long, there could be wrap-
ping around the limb, and mappable points could be marked
unmappable, but this is only likely to happen if the region
is very large (full disc for example).
The meridional anomalous velocity merid_v is expected in
microradians per sec. The zonal anomalous velocity is
equivalent to a0 and must be added to the equatorial value
for the differential rotation (minus the Carrington rate).
It might be better to have these expressed in degrees per
day or meters per sec. The rotation rate is expanded in the
customary even powers of sin (latitude), not the more
rational Legendre function expansion. Furthermore, the rate
is sidereal, and the zero-order term in the argument rate is
assumed not to include the Carrington rate (1 rotation /
25.38 days =~ 2.8653291 urad/sec). Thus the appropriate
coefficients to use for tracking under a rigid Carrington
rotation model are all 0. Tracking at fixed proper motions
requires setting a2 and a4 to 0 and a0 (and merid_v) to
0.0014368 * rate (m/s) urad/sec.
If "lat", "lon", or "latlon" basenames are selected, the
latitudes and/or longitudes of centers must all differ by at
least 0.1 degree from one another, otherwise files will be
overwritten.
With polar coordinate output the map scales don't mean a
lot.
Data quality selection via quality bitmasks or otherwise is
still unimplemented; all input images are used uncondition-
ally.
AUTHOR
Rick Bogart
HISTORY
2000-08-15 SOI Version 4.8