ud_grade

This program can upgrade or degrade the resolution of a HEALPix map.

Location in HEALPix directory tree: src/f90/ud_grade/ud_grade.f90 

FORMAT

% ud_grade [options] [parameter_file]

COMMAND LINE OPTIONS

-d

--double

double precision mode (see Notes on double/single precision modes)

-s

--single

single precision mode (default)

QUALIFIERS

nside_out =

Defines the resolution parameter for the output map. (default= 64)

infile =

Defines the name of the file containing the map to be up/degraded. (default='map.fits')

outfile =

Defines the filename for the output up/degraded map. (default='outmap.fits')

DESCRIPTION

This facility transforms the resolution of an input HEALPix map. At each step of map resolution upgrade the four output map pixels nested in one pixel of the input map are given the values of the input pixel. At each step of map resolution degradation the four input map pixels nested in one output map pixel are averaged to produce the pixel value in the output map. Caution Beware that, at this stage, the parallel tranport of the polarization (Q and U Stokes vectors) that would be necessary to describe the change in local coordinates is not implemented.

DATASETS

The following datasets are involved in the ud_grade processing.

Dataset	Description
None required

SUPPORT

This section lists those routines and facilities (including those external to the HEALPix distribution) which can assist in the utilisation of ud_grade.

mollview

IDL routine to view an up/downgraded map.

anafast

This HEALPix facility can analyse an up/downgraded map.

EXAMPLE # 1:

ud_grade

ud_grade runs in interactive mode, self-explanatory.

EXAMPLE # 2:

ud_grade filename

When `filename' is present, ud_grade enters the non-interactive mode and parses its inputs from the file `filename'. This has the following structure: the first entry is a qualifier which announces to the parser which input immediately follows. If this input is omitted in the input file, the parser assumes the default value. If the equality sign is omitted, then the parser ignores the entry. In this way comments may also be included in the file. In this example, the file contains the following qualifiers:
nside_out= 64
infile= map.fits
outfile= outmap.fits

Ud_grade transforms the HEALPix map in 'map.fits' to resolution Nside=64, no matter what the input map resolution was. The up/downgraded map is stored in 'outmap.fits'.

RELEASE NOTES

■ (Initial release HEALPix 0.90)

■ Extension to multi-dimensional maps (HEALPix 1.20)

MESSAGES

This section describes error messages generated by ud_grade

Message	Severity	Text
can not allocate memory for array xxx	Fatal	You do not have sufficient system resources to run this facility at the map resolution you required. Try a lower map resolution.