c  read_matrix subroutine
c  This program reads in the binary input matrices
c   It requires a data file and an error file.
c  created 9/96
      subroutine read_matrix(grid,grerror,nx,ny,xres,yres,xleft,
     1   xright,ytop,ybot)
      parameter (ngx=1000,ngy=700)
      character*80, fin,finerror
      integer nx, ny, iost, i, j
      real xres,yres,xleft,xright,ytop,ybot
      real grid(ngy,ngx),grerror(ngy,ngx)

c prompt user for input files
      print *,"Enter the name of the input grid data file"
      read *,fin
      print *,"Enter the name of the input gridded error file"
      read *,finerror
      iost = 10
      ioster = 11
c
c open grid file
      open(iost,file=fin,status='old',form='unformatted',iostat=icd)
      if (icd .ne. 0) then
        write(6,*) 'error opening input file  iostat= ',icd
        stop 99
      end if
c  read header
       read(iost) nx,ny,xres,yres,xleft,xright,ytop,ybot
c
c open grid error file
      open(ioster,file=finerror,status='old',
     1     form='unformatted',iostat=icd)
      if (icd .ne. 0) then
        write(6,*) 'error opening input error file  iostat= ',icd
        stop 99
      end if
c  read error file header
       read(ioster) nxe,nye,xrese,yrese,xlefte,xrighte,ytope,ybote
c
c  test that error file is compatible with data file
c  stop if they do not have the same header line
      call checkerr(nx,ny,xres,yres,xleft,xright,ytop,ybot,
     1   nxe,nye,xrese,yrese,xlefte,xrighte,ytope,ybote)
c
c  read data and errors
       do i = 1, ny
         read(iost) (grid(i,j),j=1,nx)
         read(ioster) (grerror(i,j),j=1,nx)
       enddo
        close(iost)
        close(ioster)
        return
	end