;+
; NAME:
;	AZ2CR
; PURPOSE:
;       Generates arrays of column and row numbers from arrays of
;       azimuth and zenith angle, using a geometrical transformation.
; CATEGORY:
;	
; CALLING SEQUENCE:
;	AZ2CR, YEAR, MONTH, DAY, CAMERA, FILTER, AZIMUTH, ZENANG $
;	     , COLUMN, ROW [, DEGREES=degrees [, BIN=bin [, SITE=site] ] ]
; INPUTS:
;	YEAR, MONTH, DAY: Self-evident.  Must be a 4-digit year.
;       CAMERA: The number of the camera that acquired the images
;		to be transformed.
;	FILTER:	The filter through which the images were acquired.
;       AZIMUTH: The array of azimuths, expressed in degrees E of
;		geographic N.
;       ZENANG: The corresponding array of zenith angles, expressed
;               in degrees.  ZENANG must have the same structure
;		as AZIMUTH.
; KEYWORD PARAMETERS:
;	/DEGREES: Set if angle measure in degrees is desired.
;       BIN:    If set, gives the binning factor for the image
;               relative to a 512x512 original image.  If not set,
;               a 256x256 image is assumed in calculating the column
;		and row numbers.
;       SITE:   A number specifying the location of the Polar Camera
;               on the specified date.  This information is redundant
;               but the keyword is retained for consistency with
;		older versions of this routine.
; OUTPUTS:
;       COLUMN: An array of the same structure as AZIMUTH and
;               ZENANG, giving the image column numbers of the
;		directions specified by AZIMUTH and ZENANG.
;       ROW:	An array of the same structure as AZIMUTH and
;               ZENANG, giving the image row numbers of the
;		directions specified by AZIMUTH and ZENANG.
; COMMON BLOCKS:
;	None.
; SIDE EFFECTS:
;	None.
; RESTRICTIONS:
;	The input angles must be in degrees.
; PROCEDURE:
;       The transformation parameters appropriate to the date are
;       read in, and the transformation equations applied to the
;	input AZIMUTHs and ZENith ANGles.
; MODIFICATION HISTORY:
;	Modified 93/11 from POSITION.PRO by D P Steele.
;	Documented 94/06 by D P Steele.
;       Modified 94/09/27 by D P Steele: replaced /SMALL keyword
;		with BIN=bin keyword for greater flexibility.
;	Modified by D P Steele, 18 Oct 1994 to add DEGREES keyword.
;-
PRO az2cr,year,month,day,cam,filt,az,za,cl,rw $
	 ,degrees=degrees,bin=bin,site=site,small=small

IF N_PARAMS() LT 9 THEN BEGIN
    doc_library,'az2cr'
    RETURN
    ENDIF

IF KEYWORD_SET(degrees) THEN ff=!DTOR ELSE ff=1.

; Read in mean parameters for transformation between (row,col) and (az,za)
rdmnparm,year,month,day,cam,ccol,crow,stretch,warp,camaz,site=site

camaz=camaz/ff

; JHU/APL - convert polar coordinates to rectangular
polrec3d,REPLICATE(1.,N_ELEMENTS(az)),za,az,x,y,z,degrees=degrees

rot_3d,3,x,y,z,camaz,xp,yp,zp,degrees=degrees	;rotation along the z-axis
rho=stretch*SIN(warp*za*ff)
phi=+ATAN(yp,xp)

;variables to be returned
cl=ccol-rho*SIN(phi)
rw=crow-rho*COS(phi)

IF KEYWORD_SET(bin) THEN BEGIN
    cl=cl/(bin/2)
    rw=rw/(bin/2)
    ENDIF

RETURN
END