DRAWPOLY - Draw a polygon

Description:

This routine draws a polygon using the data in the XCOL and YCOL areas to define the vertices of the region. The polygon is shaded using the current fill-area style attributes (see the FILLSTY command).

Usage:

drawpoly [fill]

Parameters:

FILL = _LOGICAL (Read)

Whether to fill the polygon or not. If TRUE then the current fill-area style attributes as set by the CHANGE command will be used. [TRUE]

PROJECTION = _CHAR (Read)

The geometry to be used for plotting the polygon. This is explained in more detail in the section on projections. Allowed values: "NONE", "TAN", "SIN", "ARC", "GLS", "AITOFF", "MERCATOR" and "STG".

[The value of the global parameter PONGO_PROJECTN is used. If PONGO_PROJECTN is not defined, the default value "NONE" is used.]

RACENTRE = _CHAR (Read)

The centre of the projection in RA (i.e. the angle must be specified as hh:mm:ss.sss). This parameter is only required for PROJECTION values other than "NONE".

[The value of the global parameter PONGO_RACENTRE is used. If PONGO_RACENTRE is not defined, the default value "0" is used.]

DECCENTRE = _CHAR (Read)

The centre of the projection in declination (i.e. the angle must be specified as dd:mm:ss.sss). This parameter is only required for PROJECTION values other than "NONE".

[The value of the global parameter PONGO_DECCENTRE is used. If PONGO_DECCENTRE is not defined, the default value "0" is used.]

Examples:

drawpoly

This draws a single polygon on the current graphics display. The polygon is filled or shaded using the current fill-hatch styles.

drawpoly projection=aitoff deccentre="12:00:00"

This draws a single polygon on the current graphics display. The polygon is filled or shaded using the current fill-hatch styles and the polygon is drawn using an AITOFF projection. The lines along the edges of the polygon are drawn as suitable arcs.

Notes:

• The XCOL and YCOL positions are assumed to be in radians.

• If a projection is used then expect the polygon to be incorrect if it crosses any discontinuities, or if the edges are severely distorted (the polygon is filled as plotted on the display surface, not the sky).