program icesat_ave
cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc
c
c                      I C E S A T _ A V E
c
c  Averages and tresholds 40 Hz ICESat data (geoid assumed removed)
c  Input:
c  
c  ifile
c  ofile
c  trsh
c
c  (c) Rene Forsberg, DNSC/Denmark, yyc apr 2006
c
cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc
      implicit double precision(a-h,o-z)
      character*72 ifile,ofile
c
      write(*,*) 'input: ifile'
      write(*,*) '       ofile'
      write(*,*) '       trsh'
      read(*,'(a)') ifile
      read(*,'(a)') ofile
      read(*,*) trsh
      open(10,file=ifile,status='old')
      open(20,file=ofile,status='unknown')
c
      iave = 0
      sumlat = 0
      sumlon = 0
      sumt = 0
      sumh = 0
      hmin = 9999
      nout = 0
c  
10    read(10,*,end=20) iday,rlat,rlon,t,h
c
      if (abs(h).gt.trsh) goto 10
      if (nout.eq.0.and.iave.eq.0) then
        idayp = iday
        tp = t
      endif
c
      iave = iave+1
      sumlat = sumlat+rlat
      sumlon = sumlon+rlon
      sumt = sumt+t
      sumh = sumh+h
      if (h.lt.hmin) hmin = h
c
      if (iday.ne.idayp.or.abs(t-tp).gt.1.d0.or.iave.ge.40) then
        if (iave.ge.1) then
          write(20,15) 
     .    iday,sumlat/iave,sumlon/iave,sumt/iave,sumh/iave,hmin,iave
15        format(i5,2f11.5,f11.2,2f9.3,i4)
          nout = nout+1
        endif
        iave = 0
        sumlat = 0
        sumlon = 0
        sumt = 0
        sumh = 0
        hmin = 9999
        tp = t
        idayp = iday
      endif
      goto 10
c
20    if (iave.ge.1) then
        write(20,15) 
     .  iday,sumlat/iave,sumlon/iave,sumt/iave,sumh/iave,hmin,iave
        nout = nout+1
      endif
      write(*,*) 'no of output records: ',nout
      end