PRO prov

; This procedure reads in the ASCII file '/jasper/cnsr3_data1/prov/prov.ascii',
; locates the breaks in the Canadian political boundaries listed
; in the file, and OPLOTs the lines onto the existing plot.  You
; must call MAP_SET first to define the projection.

COMMON provinces,lats,lons,nb,b,l

IF N_ELEMENTS(l) EQ 0 THEN BEGIN
    PRINT,'Reading provincial boundaries file...'
    OPENR,unit,'/jasper/cnsr3_data1/prov/prov.dat',/GET_LUN
    len=1
    READU,unit,len		; length of each array to follow

    lats=FLTARR(len)		; latitudes and longitudes are
    lons=lats			; FLOATs
    keys=INTARR(len)		; keys are INTs

    READU,unit,lats
    READU,unit,lons
    READU,unit,keys

    CLOSE,unit
    FREE_LUN,unit

    l=FIX(keys/10)		; interpret 3rd col as # of pts per boundary
    b=WHERE(l,nb)		; locate non-zero elements
    l=l(b)			; save only non-zero elements
ENDIF

PRINT,'Plotting provincial boundaries...'
FOR i=0,nb-1 DO BEGIN	; for each boundary segment
    s=b(i)		; define start point in lats, lons arrays
    q=b(i)+l(i)-1	; as well as quitting point
    OPLOT,lons(s:q),lats(s:q)	; overplot the boundary segment
ENDFOR

PRINT,'Done...'
RETURN
END