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track_region \- strategy module to create a time series ofmaps of a region tracked in heliographic coordinates extracted froma series of solar images
.B track_region
\fI [argument= value ...]\f
\fItrack_region\fR extracts a region fixed in some set of heliographiccoordinates from a series of solar images. The tracked region is specifiedby the radius in degrees and heliographic coordinates of the axis of aheliocentric cone. On output, a square map of a region containing thiscone is produced. In determining the size of the output map, the desiredmap scale is used to determine the smallest power-of-2 size containing therequested cone. If the scale is 0, the output scale is matched to the bestscale of the observed image at disc center.

The mapped data set is placed in a single 3-dimensional FITS file, with

time (image serial number) the most slowly varying axis. .NXR ""
.NXR "track_region command" "options"
.IP \fBin=\fIname\fR 20

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.
.IP \fBout=\fIname\fR 20

The output dataset name.

.IP \fBstart=\fItime\fR 20
.IP \fBstop=\fItime\fR 20

The desired start and stop times for data. If the input dataset is

fully specified (including sequence number range), these times need not be supplied.
.IP \fBlog=\fIstring\fR 20

The file name of the log file associated with the input dataset(s)

(default "logfile"). This log file is expected to contain centering and scaling information from the calibration of the input dataset as appropriate.
.IP \fBlat=\fIfloat\fR 20

The heliographic latitude of the center of the tracked cone.

.IP \fBlon=\fIfloat\fR 20

The heliographic longitude of the center of the tracked cone.

The heliographic coordinates are in degrees,

and are appropriate to the time of (first)
central meridian crossing of the point.
.IP \fBradius=\fIfloat\fR 20

The radius of the tracked cone, in degrees; for a typical scale of 0.12

(see below), a radius of about 15 deg corresponds to a 128*128 map.
.IP \fBscale=\fIfloat\fR 20

Scale of map (heliographic degrees / pixel) at location appropriate for 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 MtWilson or HRH or TON. (Default 0.0)
.IP \fBmap=\fIstring\fR 20

Mapping option: recognized values are "rectangular",

"Postels", "gnomonic", "stereographic", and "orthographic" (and others).

Default: "Postels".

.IP \fBtrack=\fIstring\fR 20

Tracking option: recognized values are "eulerian" and "lagrangian".

With the "eulerian" option, the entire region is tracked at a fixed

rate appropriate to the center of the tracked cone, while the "lagrangian" option tracks points at the differential rotation rate appropriate to their individual latitude.

Default: "eulerian".

.IP \fBa0=\fIfloat\fR 20
.IP \fBa2=\fIfloat\fR 20
.IP \fBa4=\fIfloat\fR 20
a0, a2, and a4 are the coefficients in a sin^2 (latitude) expansion of the differential rotation rate, minus the Carrington rotation, in microrad / 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


.IP \fBplatform=\fIstring\fR 20

Observing platform, used for observer ephemeris; valid values are "SOHO",

"HRH", "MtWilson_60", "GONG", and "TON" (and others); for multi-site networks, the ephemeris data are assumed contained in the data.

Default: "SOHO"

.IP \fBxscale=\fIfloat\fR 20

Default: read from first image in data series.

.IP \fByscale=\fIfloat\fR 20
"xscale" and "yscale" are the horizontal and vertical scale of each image, both in arcsec / pixel; if only one is present it is assumed to apply to the other. Note that the sign is interpreted, with positive values signifying that sky north and sky west correspond to increasing row and column values respectively when the plate
position angle is 0. An inverted image can be signaled by making one of the quantities negative.

Default: read from first image in data series.

.IP \fBobstime=\fItime\fR 20

Observation time. Default: read from each image.

.IP \fBplate_pa=\fIfloat\fR 20

The angle (in degrees) by which the image

would have to be rotated counterclockwise
to place sky north at the "top" (last row).

It is immaterial whether the image is

inverted or direct.

Default: read from each image.


A number of features are not yet implemented, including the Lagrangian

tracking option and the ability to specify start and stop times. The module has only been tested with one dataset, and options associated with platform recognition do not exist.

Luiz Sa and Rick Bogart

1994-09-19 SOI Version 0.9
.#$Id: track_region.1,v 1.2 1994/09/19 18:58:16 rick Exp $ .#$Source: /home/soi/CM/man/man1/RCS/track_region.1,v $ .#$Author: rick $

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