SUBROUTINE PLTWV (EF,Z,NP,NT,O,PR,PL)

C	[WATERLEVEL VIEW]
C	PROGRAM TO PRODUCE APERSPECTIVE DRAWING OF A SINGLE VALUED
C	FUNCTION DEFINED OVER A SPHERICAL SURFACE, IN SUCH A WAY AS
C	TO EXHIBIT THE ARCS OF LATIDUDE AND LONGITUDE.
C	EF(NP,NT)	ARRAY OF FUNCTION VALUES
C	Z		WATER LEVEL
C	NP		NUMBER (=2*N+1) OF POINTS ON ONE LATITUDE
C	NT		NUMBER OF POINTS ON ONE LONGITUDE
C	O(3,3)		ORTHOGONAL ROTATION MATRIX
C	PR		PROJECTION SUBROUTINE
C	PL		PEN MOVEMENT SUBROUTINE
C	[02-JUN-74]   !THD ZERBE

	EXTERNAL PR,PL
	LOGICAL	B
	DIMENSION EF(1),O(3,3)
	COMMON/VIS/ N0
	CALL VISNP (PH,TH,JP,IT,NP,NT,O)
	NH=(NP-1)/2
	CALL PR(R,P,1.0,TH,PH+0.05,O)
	B=((-0.25).LT.P).AND.(P.LE.(0.25))
	IF (TH.GT.(1.57079)) GOTO 10
	I1=1
	I2=IT
	I3=IT
	I4=NT
	GOTO 12
 10	I1=IT
	I2=NT
	I3=1
	I4=IT
 12	J1=JP
	J2=JP+NH
	J3=JP-NH-1
	J4=JP
	N0=0
	CALL VISWS (EF,Z,J1,J2,NP,I1,I2,NT,1,-1,B,O,PR,PL)
	CALL VISWS (EF,Z,J1,J2,NP,I1,I2,NT,1,1,B,O,PR,PL)
	CALL VISWS (EF,Z,J1,J2,NP,I3,I4,NT,1,1,B,O,PR,PL)
	CALL VISWS (EF,Z,J1,J2,NP,I3,I4,NT,1,-1,B,O,PR,PL)
	N0=0
	CALL VISWS (EF,Z,J3,J4,NP,I1,I2,NT,-1,-1,(.NOT.B),O,PR,PL)
	CALL VISWS (EF,Z,J3,J4,NP,I1,I2,NT,-1,1,(.NOT.B),O,PR,PL)
	CALL VISWS (EF,Z,J3,J4,NP,I3,I4,NT,-1,1,(.NOT.B),O,PR,PL)
	CALL VISWS (EF,Z,J3,J4,NP,I3,I4,NT,-1,-1,(.NOT.B),O,PR,PL)
	RETURN

	END