;+
; NAME:
;       smei_sky_hdr_check
; PURPOSE:
;       Align sky map headers for various routines
; CATEGORY:
;       camera/idl/sky
; CALLING SEQUENCE:
PRO smei_sky_hdr_check, hdrs, hdr
; INPUTS:
;       hdrs		structure; type: smei_sky_hdr
;	hdr		structure; type: smei_sky_hdr
;
; OUTPUTS:
;       hdrs=hdrs       structure or array; type: smei_sky_hdr
;
; INCLUDE:
        @compile_opt.pro                ; On error, return to caller
; PROCEDURE:
;	smei_sky_hdr_check, hdrs, hdr
;	       two headers to be compared
; MODIFICATION HISTORY:
;       FEB-2010, John Clover (UCSD/CASS)
;		Compares two hdr structures for matching cameras and
;		returns them with the same dimensions
;		Still ignorant of modes, and prefers c3 to c3s unless
;		/prefer_smoothdark was used in caller (smei_sky)
;
;-
	camloca = intarr(3)
	camlocb = intarr(3)
		for i=1,3 do begin
			;caveat, if /prefer_smoothdark not set, both smooth and unsmoothed
			;c3 are in the list and will return two locations
			;here I pick the first, which is not smoothed by default
			;since you can force it to unsmoothed with prefer.. so
			;instead assume that if it is not specified, that you should
			;use the standard skymap
			camloca[i-1] = ((where(hdrs.camera EQ i))[0] GE 0)
			camlocb[i-1] = ((where(hdr.camera EQ i))[0] GE 0)
		end
		; multiply arrays [1, 1, 0] * [1, 0, 0] returns [1, 0, 0] keep camera 1
		combined = camloca*camlocb
		; if there is no overlap, nullify both headers
		if ((where(combined EQ 1))[0] ne -1) then begin
			for i=0, n_elements(hdrs)-1 do begin
				; camera # is in hdrs[i].cameras but here hdrs[i]
				if (combined[hdrs[i].camera-1] EQ 1) THEN boost, comba, i
			end
			for i=0, n_elements(hdr)-1 do begin
				if (combined[hdr[i].camera-1] EQ 1) THEN boost, combb, i
			end
			hdrs = hdrs[comba]
			hdr = hdr[combb]
		endif else begin
			; no overlap, nullify both headers
			; smei_sky_read returns -1 for null header
			hdrs = -1
			hdr = -1
		end
END