ELPROF - Creates a radial or azimuthal profile of a two-dimensional image

Description:

This application will bin the input image into elliptical annuli, or into a `fan' of adjacent sectors, centred on a specified position. The typical data values in each bin are found (see parameter ESTIMATOR), and stored in a one-dimensional NDF  which can be examined using LINPLOT, LOOK, etc. A two-dimensional mask image can optionally be produced indicating which bin each input pixel was placed in.

The area of the input image which is to be binned is the annulus enclosed between the two concentric ellipses defined by parameter RATIO, ANGMAJ, RMIN and RMAX. The binned area can be restricted to an azimuthal section of this annulus using parameter ANGLIM. Input data outside the area selected by these parameters is ignored. The selected area can be binned in two ways, specified by parameter RADIAL:

• If radial binning is selected (the default), then each bin is an elliptical annulus concentric with the ellipses bounding the binned area. The number of bins is specified by parameter NBIN and the radial thickness of each bin is specified by WIDTH.

• If azimuthal binning is selected, then each bin is a sector (i.e. a wedge-shape), with its vertex given by parameters XC and YC, and its opening angle given by parameters WIDTH. The number of bins is specified by NBIN.

Usage:

elprof in out nbin xc yc

Parameters:

ANGLIM( 2 ) = _REAL (Read)

Defines the wedge-shaped sector within which binning is to be performed. The first value should be the azimuthal angle of the clockwise boundary of the sector, and the second should be the azimuthal angle of the anti-clockwise boundary. The angles are measured in degrees from the x-axis, and rotation from the x-axis to the y-axis is positive. If only a single value is supplied, or if both values are equal, the sector starts at the given angle and extends for 360 degrees. [0.0]

ANGMAJ = _REAL (Read)

The angle between the x-axis and the major axis of the ellipse, in degrees. Rotation from the x-axis to the y-axis is positive. [0.0]

ESTIMATOR = LITERAL (Read)

The method to use for estimating the output pixel values. It can be either "Mean" or "Weighted Mean". If the weighted mean option is selected but no variances are available in the input data, the unweighted mean will be used instead. ["Mean"]

IN = NDF (Read)

The input NDF containing the two-dimensional image from which a profile is to be generated.

MASK = NDF (Write)

An output NDF of the same shape and size as the input NDF indicating the bin into which each input pixel was placed. For radial profiles, the bins are identified by a mask value equal to the radius (in pixels) measured on the major axis, at the centre of the annular bin. For azimuthal profiles, the bins are identified by a mask value equal to the angle from the x-axis to the centre of the sector-shaped bin (in degrees). If a null value is supplied, then no mask NDF is produced. [!]

MTITLE = LITERAL (Read)

A title for the mask NDF. If a null value is given, the title is propagated from the input NDF. This is only prompted for if MASK is given a non-null value. ["Mask created by KAPPA - Elprof"]

NBIN = _INTEGER (Read)

The number of radial or azimuthal bins required.

OUT = NDF (Write)

The output one-dimensional NDF containing the required profile. For radial profiles, it has associated axis information describing the radius, in pixels, at the centre of each annular bin (the radius is measured on the major axis). For azimuthal profiles, the axis information describes the azimuthal angle, in degrees, at the centre of each sector-shaped bin. It will contain associated variance information if the input NDF has associated variance information.

RADIAL = _LOGICAL (Read)

Specifies the sort of profile required. If RADIAL is TRUE, then a radial profile is produced in which each bin is an elliptical annulus. Otherwise, an azimuthal profile is produced in which each bin is a wedge-shaped sector. [TRUE]

RATIO = _REAL (Read)

The ratio of the length of the minor axis of the ellipse to the length of the major axis. It must be in the range 0.0 to 1.0. [1.0]

RMAX = _REAL (Read)

The radius in pixels, measured on the major axis, at the outer edge of the elliptical annulus to be binned. If a null value (!) is supplied the value used is the distance from the ellipse centre (specified by XC and YC) to the furthest corner of the image. This will cause the entire image to fall within the outer edge of the binning area. [!]

RMIN = _REAL (Read)

The radius in pixels, measured on the major axis, at the inner edge of the elliptical region to be binned. [0.0]

TITLE = LITERAL (Read)

A title for the output profile NDF. If a null value is supplied the title is propagated from the input NDF. ["KAPPA - Elprof"]

WIDTH = _REAL (Read)

The width of each bin. If a radial profile is being created (see parameter RADIAL) this is the width of each annulus in pixels (measured on the major axis). If an azimuthal profile is being created, it is the opening angle of each sector, in degrees. If a null (!) value is supplied, the value used is chosen so that there are no gaps between adjacent bins. Smaller values will result in gaps appearing between adjacent bins. The supplied value must be small enough to ensure that adjacent bins do not overlap. The supplied value must be at least 1.0. [!]

XC = _REAL (Read)

The x pixel co-ordinate of the centre of the ellipse, and the vertex of the sectors.

YC = _REAL (Read)

The y pixel co-ordinate of the centre of the ellipse, and the vertex of the sectors.

Examples:

elprof galaxy galprof 20 113 210 angmaj=49 rmin=10 rmax=210 ratio=0.5

This example will create a one-dimensional NDF called galprof containing a radial profile of the two-dimensional NDF called galaxy. The profile will contain 20 bins and it will be centred on the pixel co-ordinates (113,210). Each bin will be an annulus of an ellipse with axis ratio of 0.5 and inclination of 49 degrees to the x-axis. The image will be binned between radii of 10 pixels, and 210 pixels (measured on the major axis), and there will be no gaps between adjacent bins (i.e. each bin will have a width on the major axis of about 10 pixels).

elprof galaxy galprof 10 113 210 radial=f anglim=20 rmin=50 rmax=60

This example also creates a one-dimensional NDF called galprof, this time containing an azimuthal profile of the two-dimensional NDF called "galaxy", containing 10 bins. Each bin will be a wedge-shaped sector with vertex at pixel co-ordinates (113,210). The clockwise edge of the first bin will be at an angle of 20 degrees to the x-axis, and each bin will have a width (opening angle) of 36 degrees (so that 360 degrees are covered in total). Only the section of each sector bounded by radii of 50 and 60 pixels is included in the profile. In this case the default value of 1.0 is accepted for parameter RATIO and so the bins will form a circular annulus of width 10 pixels.

Related Applications

ESP: ELLFOU, ELLPRO, SECTOR.

Implementation Status:

• This routine correctly processes the DATA, VARIANCE, TITLE, UNITS, WCS (in radial mode only) and HISTORY  components of the input NDF to the output profile NDF. WCS information is also propagated to the output mask NDF.

• WCS information is currently lost by this application.

• Processing of bad pixels and automatic quality masking are supported.

• All non-complex numeric data types can be handled. Arithmetic is performed using single-precision floating point.