ADD_DBM - Generate a chopped image from a single beam map

Description:

Create a chopped image from a single beam input map. Can be used to create a dual-beam (e.g. a simlated scan map image) or a triple-beam map (e.g. a simulated jiggle map image).

For dual-beam it simply finds the signal detected at each pixel by looking at the difference between the pixels nearest to each chop beam. This calculates a middle beam response. (ie the response at each pixel is the difference between the L and the R beams).

For the triple-beam response the signal is the difference between the middle pixel and half the values measured in the negative beams. Set NBEAMS to 3 to use triple-beam response.

This task can be used to generate test data for remdbm.

Usage:

add_dbm in chop pa out

Parameters:

CHOP = REAL (Read)

Chop throw in pixels of the input image. There is no default. The range of this parameter should lie between 1 and the size of the input image.

IN = NDF (Read)

Input single beam image.

MSG_FILTER = CHAR (Read)

Message filter level. Options are QUIET, NORMAL and VERBOSE. Default is NORM.

NBEAMS = INTEGER (Read)

When NBEAMS=2 a dual-beam response is calculated. When NBEAMS=3 a triple-beam response is calculated. Default is 3.

OUT = NDF (Write)

Output Dual beam image. Default output name is input name plus _dbm_int(pa)_int(chop).

PA = REAL (Read)

Position angle of chop throw. Positive is anti-clockwise starting from North. The angle should be specified in degrees.

PIXSIZE = REAL (Read)

Pixel size in arcseconds. This is required for compatibility with remdbm (since the CHOP_THR FITS keyword has to be in arcseconds rather than pixels and REMDBM requires SCUPIXSZ FITS keyword). A null value will be treated as 1 arcsec. Default is to use the value of SCUPIXSZ from the FITS header (if present).

Examples:

add_dbm gaussian 0 30 dbm_out

Generate a dual beam image from the single beam 'gaussian' input NDF using a 30 pixel chop at 0 degrees. Write the resulting image to dbm_out.sdf.

add_dbm image 90 45 3bm_out nbeams=3

Generate a triple-beam image with throw 45 and position angle 90 degrees.

Notes:

• The output images are compatible with REMDBM.

• All extensions and AST/WCS information are propogated to the output image.

• A variance array is created if present in the input image.

• If a quality array is present in the input image it is used to generate a bad pixel mask in the output image and is removed.

• Bad pixels in the input image are treated as zeroes for the dual beam calculation.

Related Applications

SURF: remdbm