mProjectCube1

Usage

Overview

mProjectCube reprojects a single cube to the scale defined in a FITS header template file (read more about header templates here). The program produces a pair of files: the reprojected cube and an "area" image consisting of the fraction input pixel sky area that went into each output pixel. The "drizzle" algorithm is implemented. The algorithm proceeds by mapping pixel corners (as adjusted by drizzle, if called) from the input pixel space to the output pixel space, calculating overlap area with each output pixel, and accumulating an appropriate fraction of the input flux into the output cube pixels. In addition, the appropriate fraction of the input pixel area is accumulated into the area image pixels. Projection of points from input pixel space to output pixel space is calculated in two steps: first map from input pixel space to sky coordinates; second map from sky coordinates to output pixel space.

One situation that has happened often enough to warrant special note: It is possible to define a FITS header with the reference location off the image. In particular, people often reference cylindrical projections (e.g., CAR, CEA) to location (0.,0.) (e.g., the Galactic center). This is not wrong in itself but does lead to extremely large pixel offsets (e.g., in the hundreds of thousands). Related to this, if you extract a header from an image with large offsets of this type, it is unlikely that you can simply change projection types without also adjusting the reference location/offsets. Most likely, you will end up witr the reprojected data all being off-scale.

Options

-z factor

Processing is done utilizing the drizzle algorithm. factor is a floating point number; recommended drizzle factors are from 0.5 to 1.

-d level

Causes additional debugging information to be printed to stdout. Valid levels are 1-5 (for higher debugging levels, it is recommended to redirect the output to a file).

-s statusfile

Output and errors are written to statusfile instead of being written to stdout.

-h hdu

Use the specified FITS extension (default is to use the first HDU with image data)

-x scale

Apply a correction factor of scale to each pixel.

-w weightfile

Path to a weight map to be used when reading values from the input image.

-W fixed-weight

Use constant weight value for the whole image.

-t threshold

Pixels with weights below threshold will be treated as blank.

-X

Makes the output region (originally defined in the header template) big enough to include all of the input images.

-e

Process the data as total energy rather than the default energy density (scale values by relative pixel areas).

-f

Output the full region requested even if there is a border of NULL values (default is to shrinkwrap to just the pixels with values).

Arguments

in.fits

Input FITS file to be reprojected.

out.fits

Path of output FITS file to be created.

hdr.template

FITS header template to be used in generation of output image

Result

Two files are created as output: the reprojected FITS file (out.fits), and an "area" image (out_area.fits) which records the amount of coverage (in output pixel space) provided by the input images.

Messages

OK

[struct stat="OK", time=seconds]

ERROR

Drizzle factor string (string) cannot be interpreted as a real number

ERROR

Weight threshold string (string) cannot be interpreted as a real number

ERROR

Flux scale string (string) cannot be interpreted as a real number

ERROR

Cannot open status file: statusfile

ERROR

HDU value (hdu) must be a non-negative integer

ERROR

No overlap

ERROR

Not enough memory for output data image array

ERROR

Not enough memory for output area image array

ERROR

Output wcsinit() failed.

ERROR

Input wcsinit() failed.

ERROR

FITS library error

ERROR

All pixels are blank

ERROR

Template file not found

ERROR

Image file in.fits missing or invalid FITS

ERROR

Weight file weightfile missing or invalid FITS

Examples

$ mProjectCube rawdir/real_orig.fits projdir/base_unity.fits templates/galactic_orig.txt

[struct stat="OK", time=143]