program read_ssh
c
c	Peter M. Woiceshyn	Auguust 26, 2002
c       818-354-1450
c	Peter.M.Woiceshyn@jpl.nasa.gov
c
c   Sample program provides FORTRAN statements used to read in TOPEX/POSEIDON
c	 sea surface height data in centimeters.
c
c   The 2001 TOPEX/POSEIDON data are on a 540 X 540 element grid with the
c	origin at
c
c   	-89.8333 deg (S) latitude and 0.3333 degrees (E) longitude.
c
c      	lat grid interval, dlat = 1/3
c      	lon grid interval, dlon = 2/3
c
c
c	GRID LIMITS
c
c	lat limits: -89.8333 (S)  to  89.8333 (N)
c       lon limits:   0.3333 (E)  to 359.6667 (E)
c
c
c	DATA LIMITS
c
c	lat limits: -65.8333 (S)  to  65.8333 (N)
c       lon limits:   0.3333 (E)  to 359.6667 (E)
c
c   There are 12 monthly data files for year 2001.
c
C----------------------------------------------------------------------C
c
c   Declarations:

	REAL ssh(540,540)    ! Topex data is in cm.

c                	       The values greater than or equal to 32767
c				   indicates no data
c
C----------------------------------------------------------------------C

	REAL del1, del2
	REAL lon(540), lat(540)
C	
	INTEGER*2    lon2, lat2
c
	
	CHARACTER*2  c_mo(12)
	CHARACTER*2  yc
	CHARACTER*20 f_in
	CHARACTER*4  f_label
	CHARACTER*4  suff

C----------------------------------------------------------------------C

	DATA   c_mo/'01','02','03','04','05','06',
     &	            '07','08','09','10','11','12'/


C----------------------------------------------------------------------C

	     yc = '01'
	
	   suff = '.dat'

        f_label = yc//c_mo(1)	! 0001  Jan 2001
  
           f_in = 'ssh'//f_label//suff

C----------------------------------------------------------------------C

	     lon2 = 540
	     lat2 = 540
  
	     del1 = 1.0/3.0
	     del2 = 2.0/3.0
  
	   PRINT *,' ' 
	   PRINT *,'    longitude array dimension =  ',lon2
	   PRINT *,'     latitude array dimension =  ',lat2
	   PRINT *,'           delta latitude deg = ',del1
	   PRINT *,'          delta longitude deg = ',del2
	   PRINT *,' ' 

C  Construct lat & lon arrays

	DO jj = 0, lat2 - 1
	
                   lat(jj+1) = jj*del1 - 90.0 + del1/2.0
	ENDdo

	DO ii = 0, lon2 - 1
	
                   lon(ii+1) = ii*del2 + del2/2.0
	ENDdo
  
c
c
c	Lat range:	-89.8333(S) to  89.8333(N) degrees 
c
c	Lon range:	  0.3333(E) to 359.6667(E) degrees 
c
c
	   PRINT *,' ' 
	   PRINT *,'    Reading file: ',f_in
	   PRINT *,' ' 

	       OPEN(22,file=f_in,form='unformatted')

		      read(22) ssh
	
	       CLOSE(22)
	       
	DO j = 270, 271
	     DO i = 1, 5

	  WRITE (6,'(A7,I5,2x,A7,I5,2x,A7,F8.2,2X,A7,F8.2,2X,A7,F10.2)') 
     &       '   i = ', i,'   j = ', j,
     &       ' lat = ', lat(j),' lon = ', lon(i),
     &          ' ssh = ',ssh(i,j)
	       
	     ENDDO
	        WRITE (6,'(A2)') ' ' 
	ENDDO
	        WRITE (6,'(A2)') ' ' 
C----------------------------------------------------------------------C
	       
	STOP

	END

C----------------------------------------------------------------------C
C
C  Output from executing this program:
C
C host{wd21pw}432> read_ssh.x
c 
c    longitude array dimension =    540
c     latitude array dimension =    540
c           delta latitude deg =    0.333333
c          delta longitude deg =    0.666667
c 
c 
c     Reading file: ssh0101.dat     
c  
c   i = 1     j = 270   lat = -0.17   lon = 0.33   ssh =     6.10
c   i = 2     j = 270   lat = -0.17   lon = 1.00   ssh =     5.76
c   i = 3     j = 270   lat = -0.17   lon = 1.67   ssh = 32767.00
c   i = 4     j = 270   lat = -0.17   lon = 2.33   ssh =     1.38
c   i = 5     j = 270   lat = -0.17   lon = 3.00   ssh = 32767.00
  
c   i = 1     j = 271   lat =  0.17   lon = 0.33   ssh = 32767.00
c   i = 2     j = 271   lat =  0.17   lon = 1.00   ssh =     5.29
c   i = 3     j = 271   lat =  0.17   lon = 1.67   ssh = 32767.00
c   i = 4     j = 271   lat =  0.17   lon = 2.33   ssh =     1.26
c   i = 5     j = 271   lat =  0.17   lon = 3.00   ssh = 32767.00
c  
c 
C host{wd21pw}433> 
C
C----------------------------------------------------------------------C