program rtopo2
c
c     read formatted version of etopo2

c     Rows of data (latitude lines) are read one by
c     one starting at 89 58' North and stepping southward
c     by 2'. There are 5400 latitude lines.  The 89 58'
c     South line is not given, elevation 2810 meters can
c     be assumed.
c     There are 10800 longitude points along each latitude
c     line. The first is 180 West, second 179 58' West, etc.
c
c     Depth and elevations are in meters
 
      
      parameter (ilon=10800,ilat=5400)
      dimension itopo(ilon)
c      dimension idepth(ilon,ilat)
      
      open(20,file='etopo2.dat')

c     specific region to be printed
      alonl = -90.0
      alonr = -60.0
      alatt = 60.0
      alatb = 30.0

      if(alonl.lt.-180..or.alonr.gt.180.)then
        print*,' longitude specification error +- 180'
	print*,' alonl, alonr : ',alonl,alonr
	stop
      endif	
      if(alatt.gt.90..or.alatb.lt.-90.)then
        print*,' latitude specification error +- 90'
	print*,' alatt, alatb : ',alatt,alatb
	stop
      endif
      
      write(*,49)alatb,alonl,alatt,alonr
49    format('Sample Data             :'/,
     *       'Column and Row spacing  : 2.0 degrees'/,
     *       'SW corner (lat/lon)     :',2f6.0/,
     *       'NE corner (lat/lon)     :',2f6.0)


      ilonl = nint(alonl + 180.)*30 + 1
      ilonr = nint(alonr + 180.)*30 + 1
      ilatb = nint(90.- alatb)*30 + 1
      ilatt = nint(90.- alatt)*30 + 1
      if(ilonr.eq.ilon+1)ilonr=ilon
      if(ilatb.eq.ilat+1)ilatb=ilat

      do j=1,ilat
         read(20,'(15i6)')(itopo(i),i=1,ilon)
	 
         if(j.gt.ilatb)go to 60  !stop read data once min. latitude found
	 
c        print some data on a 2 degree grid
         if(j.ge.ilatt.and.j.le.ilatb.and.mod(j,60).eq.0)then
          write(*,'(24i6)')(itopo(i),i=ilonl,ilonr,60)
         endif

c        move latitude line data into depth 2-d array
c        uncomment 'dimension depth (i,j)' above to use this feature
c
c         do i=1,ilon
c	  idepth(i,j)=itopo(i)
c	 enddo
	  	 
      enddo

60    print*,'Processing completed: '      
           
      stop
      end