ARROWS
Name
ARROWS
Purpose
To display "weathervane" directional arrows on an astronomical image
Explanation
Overlays a graphic showing orientation of North and East.
Calling Sequence
ARROWS,h, [ xcen, ycen, ARROWLEN= , CHARSIZE= COLOR= , /DATA
FONT=, /NORMAL, /NOTVERTEX, THICK= ]
Inputs
h - FITS header array, must include astrometry
Optional Inputs
xcen,ycen - numeric scalars, specifying the center position of
arrows. Position in device units unless the /NORMALIZED
keyword is specified. If not supplied, then ARROWS
will prompt for xcen and ycen
Optional Keyword Inputs
arrowlen - length of arrows in terms of normal Y size of vector-drawn
character, default = 3.5, floating point scalar
charsize - character size, default = 2.0, floating point scalar
color - color name or number for the arrows and NE letters. See
cgCOLOR() for a list of color names.
Data - if this keyword is set and nonzero, the input center (xcen,
ycen) is understood to be in data coordinates
font - IDL vector font number (1-20) to use to display NE letters.
For example, set font=13 to use complex italic font.
NotVertex - Normally (historically) the specified xcen,ycen indicated
the position of the vertex of the figure. If this
keyword is set, the xcen,ycen coordinates refer to a sort
of 'center of mass' of the figure. This allows the
figure to always appear with the area irregardless of
the rotation angle.
Normal - if this keyword is set and nonzero, the input center
(xcen,ycen) is taken to be in normalized coordinates. The
default is device coordinates.
thick - line thickness, default = 2.0, floating point scalar
Outputs
none
Example
Draw a weathervane at (400,100) on the currently active window,
showing the orientation of the image associated with a FITS header, hdr
IDL> arrows, hdr, 400, 100
Method
Uses EXTAST to EXTract ASTrometry from the FITS header. The
directions of North and East are computed and the procedure
ONE_ARROW called to create the "weathervane".
Procedures Used
GETROT - Computes rotation from the FITS header
ONE_ARROW - Draw a labeled arrow
ZPARCHECK
Revison History
written by B. Boothman 2/5/86
Recoded with new procedures ONE_ARROW, ONE_RAY. R.S.Hill,HSTX,5/20/92
Added separate determination for N and E arrow to properly display
arrows irregardless of handedness or other peculiarities and added
/NotVertex keyword to improve positioning of figure. E.Deutsch 1/10/93
Added /DATA and /NORMAL keywords W. Landsman July 1993
Recognize GSSS header W. Landsman June 1993
Added /FONT keyword W. Landsman April 1995
Modified to work correctly for COLOR=0 J.Wm.Parker, HITC 1995 May 25
Work correctly for negative CDELT values W. Landsman Feb. 1996
Use GETROT to compute rotation W. Landsman June 2003
Restored /NotVertex keyword which was not working after June 2003 change
W. Landsman January 2004