AIPS HELP file for FETCH in 31DEC24
As of Thu Apr 25 22:22:43 2024
FETCH: Task to read an external image in a flexible format
INPUTS
DATAIN Input file name (Non-AIPS)
OUTNAME Output image name (name)
OUTCLASS Output image name (class)
OUTSEQ -1.0 9999.0 Output image name (seq. #)
OUTDISK 0.0 9.0 Output image disk unit #.
HELP SECTION
FETCH
Task: Task to read an image from an external text file. This
file contains a header section defining to image followed
by the image.
Adverbs:
DATAIN.....A file external to the AIPS system from which the image
can be read. Use of DATAIN depends on the host operating
system.
OUTNAME....Output image name (name). Standard behavior
with default = 'FETCH MAP'.
OUTCLASS...Output image name (class). Standard defaults.
OUTSEQ.....Output image name (seq. #). 0 => highest unique.
OUTDISK....Disk drive # of output image. 0 => highest number
with sufficient space.
EXPLAIN SECTION
FETCH: Task reads an external, formatted file containing an
image and converts it to an AIPS image file.
DOCUMENTOR: W. D. Cotton, NRAO.
RELATED PORGRAMS: AIPS, All AIPS image tasks.
PURPOSE
FETCH is designed as a skeleton task to allow a user to
put an image or image-like data into the AIPS system. The image
is expected to be stored in row order in a formatted text file
and to contain a header section which describes the image (see
below). The data may be written in a variety of formats.
Blanking is supported.
Currently the data must not wrap accross multiple lines of the
text file
COMMENTS
DATAIN:
The user must supply a text file containing the image and
its description. The header section of the input file contains
a series of keyword-value pairs to define the image followed by
the data in row order. The input file can be specified as
follows shown in the following examples:
DATAIN='disk$res:[username]image.dat' (VMS)
DATAIN='myarea:image.dat' (Unix)
where MYAREA is an environment variable set before
starting AIPS e.g.:
percentsetenv MYAREA /mnt/username
Note also: in UNIX all files whose names are pased
to AIPS should have names containing only upper case
characters.
The header portion of the image file contains a number of
keyword-value pairs in free format and in arbitrary order
terminating with a '/' character. Keywords which MUST appear in
every image are:
NAXIS = n (The number of axes in the image, up to
7 are allowed)
DIM = m1, m2, ... (The dimension of each axis used.)
FORMAT = 'r?w.d' (The FORTRAN format to be used to read
the data. r = the repeat count; ? may
be either I, F, E, or D; w = the width
of each value in characters; d = the
location of the decimal point. This
format will be repeated as many timeas
as necessary, starting a new line each
time, to read a row of the image.
Optional keywords are:
OBJECT = 'name' (The name of the object 8 char. max)
TELESCOP = 'name' (The name of the telescope used 8 char
max)
INSTRUME ='name' (The instrument used, 8 char. max)
OBSERVER='name' (The observers name, 8 char. max.)
UNITS = 'units' (The units of the image, 8 char max)
EPOCH = xxxx.x (The mean Epoch of the coordinates)
CRTYPE='a','b'... (The axis type (label) of each axis,
8 char. max.)
CRVAL = x.x, y.y... (The coordinate values at the reference
pixel on each axis, angles are in
degrees.)
CRINC = x.x, y.y ...(The increment in coordinate values
between successive pixels. Note: use a
negative increment for the RA axis.)
CRREF = x.x, y.y... (The reference pixel on each axis, need
not be an integer.)
CRROT = x.x, y.y... (The rotation; by convention the
rotation angle on the sky is
associated with the declination or
latitude-like axis.)
SCALE = x.x (A scale factor to be applied to the
values read mostly useful when the
data is in integer form.)
OFFSET = y.y (An offset to be added to the values
read after any scaling.)
BLANK = b.b The blanked (undefined) value BEFORE
any scaling and offset.
The header section is terminated by a '/'. Comments may be
included preceded by a '!'. Following this is the data stored
by row (first axis) with the other axes given with the lower
numbered axes varying the fastest. A simple example follows:
! Required keywords
NAXIS = 2 DIM = 5,5 FORMAT='5F5.2'
! Optional keywords
OBJECT='junk' TELESCOP='thin air' UNITS='JY/STR'
OBSERVER='Phantom'
EPOCH=2000.0
CRTYPE='RA---TAN','DEC--TAN'
CRVAL=180.0,40.0
CRINC=-0.1,0.1
CRREF=3.0,3.0
/
1.10 1.20 1.30 1.40 1.50
2.10 2.20 2.30 2.40 2.50
3.10 3.20 3.30 3.40 3.50
2.10 2.20 2.30 2.40 2.50
1.10 1.20 1.30 1.40 1.50
SIZE RESTRICTIONS
=================
Currently, FETCH will read images with dimensions less than or equal
to 1024 on a side with up to 16384 characters on each line.