C
C PROGRAM "cnvrnx3-rnx2" ===== Version 2.0 ===================
C
C Program for reading a RINEX 3 file and creating a GPS-only copy that
C is then converted to Rinex 2.
C The result is a version 2 and a version 3 file
C with only the GPS data of types: C1, P1, P2, C2, L1, L2, C5, L5, S1, S2 or S5,
C if present in the original RINEX 3 file (absent C2, P2, L2 either of L2C 
C or "heritage L2", blank columns are created for them, for compatibility in 
C some special cases).
C
C The line command to launch this program is:
C
C cnvrnx3-rnx2 rnxv3 i
C
C Where: "rnxv3" is the 12-character name of the input RINEX 3 file 
C                to be processed;
C        "i"     is a two-character flag signaling the type and number 
C                of output files, and whether the "heritage" 
C                or the L2C phase are to be used. See details below.
C
C ALL ARGUMENTS MUST BE PRESENT: They have no default values.
C
C In the code below, "i" is called "icreate".
C There are six output options, depending on the value of flag "i":
C
C  i = +0  to save in RINEX 2.11 both L2 phase and L2C phase (as "LC").
C
C  i = -0  NOT to save in RINEX 2.11 the L2C code and phase.'
C          A blank column "T2" is created instead of "C2", to symplify the code.' 
C
C  i = 30  A GPS-only RINEX 3 version is created.
C
C  i = 1   to output the  RINEX 2 GPS-only as a permanent file
C                (the GPS-only RINEX 3 file is a scratch file).
C  i = 2   to output both RINEX 2 and 3 GPS-only permanent files.
C
C  i =-1, i = -2  Same as = 1, =2 above, but forcing the use of    NOT IN USE
C                  the phase of L2C whenever possible.             NOT IN USE
C
C Both output files names begin with that of the original file, 
C with ".gps.rnx" or ".gps.rnx3" added at the end, to identify them clearly.
C
C Doppler data are NOT copied to the output RINEX 2 file.
C
C SPECIAL HEADER COMMENT RECORDS:
C
C The header of the RINEX 2 version generated with this program contains a 
C number of COMMENT records with information complementary to that in the
C regular RINEX 2 header records, e.g. a listing the original RINEX 3
C 3-letter-code data types that were converted to the 2-letter ones in the 
C "# / TYPES OF OBSERV" record. Also clarifying the kind of L2 phase data:
C "heritage" or L2C; whether the L2 phase from L2C requires a 1/4 wave 
C correction or not; etc.
C
C The user has to select which rinex 3 data types are going to be
C copied to the rinex 2 file by "commenting out" the type of all unwanted
C rinex 3 data in the header of their file, changing the name of the type 
C labels first letter to a "T". Example:  L1C -> T1C, S1C ->  T1C 
C to deselect L1C, S1C.
C This is not necessary for any type of Doppler: all of those are automatically
C excluded from the RINEX 2 ouput file.
C
C THERE HAS TO BE at most only one type of data in the header
C for each of basic type groups "C1", "P1" and  "L1",
C provided the respective phases and codes are truly present
C (i.e., with both listed in the header, and their data columns that are not 
C all blanks.
C -- Exception: C2, L2, P2. There should be a column for each of these, even if 
C it is all blanks; if there is not one in the original Rinex 3, one will be
C created automatically by this program in the Rinex 2 version.
C
C Due to uncertainty with the treatment by receiver manufacturers 
C of the 1/4 cycle offset between the old and the new civilian L2 phase data,
C at least for now, it is safest to choose the "heritage" L2 phase, if
C available, and not the L2 of L2C. So this program makes that choice
C automatically, unless the user expressly request the use of the L2C phase 
C through the command line, as explained above.
C If there are no P2, L2 heritage data in the RINEX 3 file, then C2 and
C the phase of L2C are used instead, automatically (this takes care of two
C future situations: when most or all GPS satellites transmit L2C, and when the
C heritage signals in L2 are no longer supported).
C
C I the user choses the option "+0" in the command line, both the "heritage" 
C L2 phase (as "LC") and the L2C phase are saved in the output RINEX 2.11 file.
C
C     ************** Oscar L. Colombo - V 1.0 January 2012 **************
C     ************** Oscar L. Colombo - V 2.0 June 2012    **************
C
      implicit real*8(a-h,o-z)
C
      character*1   cl2conly,charmin
      character*2   cicreate
      character*4   char4
      character*7   stat
      character*12  rnxfilen,rnxfilev3
      character*21  rnx2fileout,rnx3fileout
      character*80  headrec,header(100),rnxhead
      character*200 typestring
      character*450 datarecs(30),datarec,recout,record
C
      dimension nprnc2(32)
      data ihead/1/,inunit/10/,interval/0/,iendheader/0/,
     .ibad/0/,nl2cprn/0/,nprnc2/32*0/,l2cnot/0/
C
      write(0,'(" ")')
      write(0,'(" Program ""CNVRNX3-RNX2"" V1.0")')
      write(0,'(" for converting RINEX 3 ",
     ."to RINEX 2")')
      write(0,'(" Copyright (C) 2012 Oscar L. Colombo.")')
      write(0,'(" ")')
C
C WINDOWS (Intel Visual Fortran)          ! Comment or uncomment
      call getarg(1,rnxfilev3,istatus1)   ! the following statements
      call getarg(2,cicreate,istatus2)    ! to switch from WINDOWS to UNIX/LINUX
    5 continue
      if(istatus1.gt.12.or.istatus2.ne.2.
     .or.ibad.eq.1) then
C  WINDOWS
C  UNIX/LINUX (Gfortran) 
C     call get_command_argument(1,rnxfilev3,12,istatus1)
C     call get_command_argument(2,cicreate,2,istatus2)
C   5 continue
C     if(istatus1.ne.0.or.istatus2.ne.0.
C    .or.ibad.eq.1) then
C  UNIX/LINUX
C  UNIX/LINUX (G77) 
c     call getarg(1,rnxfilev3)
c     call getarg(2,cicreate)
c   5 continue
c     if(ibad.eq.1) then
C  UNIX/LINUX
      print*,' '
      print*,' ERROR in line command "cnvrnx3-rnx2"'
      print*,' The correct command is: '
      print*,' '
      print*,'"cnvrnx3-rnx2  rnxv3 i"'
      print*,' '
      print*,' "rnxv3",   = Name of the RINEX file',
     .' to be converted -- up to 12 characters long.'
      print*,' '
      print*,' "i"        =  2-character flag.'
      print*,' '
      print*,' To copy L2 and the phase of L2C if both present:'
      print*,'  i = +0  (and only the RINEX2 file is created) '
      print*,' NOT to copy any L2C data, even if they are present:'
      print*,'  i = -0  (and only the RINEX2 file is created) '
      print*,' To create a RINEX 3 file with only the GPS data:'
      print*,'  i = 30 '
      print*,' To copy the "heritage" L2 phase whenever possible:'
      print*,'  i = +1 if only the RINEX2 file is created;'
      print*,'  i = +2 if both RINEX2 & RINEX3 files are ',
     .'created.'
c     print*,' To copy as "L2" the phase of L2C, whenever possible:'
c     print*,'  i = -1 if only the RINEX2 file is created;'
c     print*,'  i = -2 if both RINEX2 & RINEX3 files are ',
c    .'created.'
      print*,' '
      print*,' The converted RINEX 2.11 file does not include Doppler '
      print*,' data.'
      print*,' '
      print*,' NOTE: If more than one type of L1 phase and S/N data is'
      print*,' present: one of L1(C,Y,M,W,P) and the corresponding '
      print*,' S1(C,Y,M,W,P)'
      print*,' MUST be chosen, deselecting the others by changing'
      print*,' the first letter in their labels to a "T" '
      print*,' in the header of the input Rinex 3 file.'
      print*,' Example: L1C -> T1C, S1C ->  T1C to select L1W, S1W .'
      print*,' ALSO: one must choose just one S2(C,Y,M,W,P,X,L,S).'
      print*,' EXCEPT when option "+0" is chosen in the command line.'
      print*,' With this option, it is OK to select one of S2(Y,M,W,P)'
      print*,' and one of S2(C,X,L,S).'
      print*,' '
      print*,' Try again.'
      print*,' '
      stop
      endif
      read(cicreate,'(a1,i1)') charmin,kicreate
      if(charmin.ne.'+'.and.charmin.ne.'-'.and.charmin.ne.'3') then
      ibad = 1
      go to 5
      endif
      read(cicreate,'(i2)') icreate
      if(icreate.eq.30) icreate = 0
      rnxfilen = rnxfilev3
      if(iabs(icreate).gt.2) then
      ibad = 1
      go to 5
      endif
C
      l2cmust = 0
C!!!?
      if(icreate.lt.0) then
      print*,' '
      print*,' The option chosen does not work properly yet.'
      print*,' SORRY '
      print*,' '
      print*,' !!!!!! JOB ABANDONED !!!!!!'
      print*,' '
      stop
      endif
C!!!?
      if(icreate.lt.0) l2cmust = 1
      if(icreate.eq.0) l2cmust = 2
      l2conly = 1
      nol2c   = 1
C!!!
c      print*,' charmin, icreate ',charmin,icreate
C!!!
      if(charmin.eq.'-'.and.iabs(icreate).eq.0) then
      l2cnot = 1
      l2cmust = 0
      endif
      kikiriki = 0
      if(charmin.eq.'3') then
      l2cnot = 0
      l2cmust = 0
      l2conly = 0
      kikiriki = 1
      endif
C!!!
c     print*,' l2cnot, l2conly, l2cmust ',l2cnot,l2conly,l2cmust
C!!!
C
      write(rnx3fileout,'(a7,"0",a4,".gps.rnx3")') rnxfilen(1:7),
     .rnxfilen(9:12)
      write(rnx2fileout,'(a7,"0",a4,".gps.rnx2")') rnxfilen(1:7),
     .rnxfilen(9:12)
C
      if(iabs(icreate).eq.1.or.icreate.eq.0)   stat = 'scratch'
      if(iabs(icreate).eq.2.or.charmin.eq.'3') stat = 'unknown'
C
      open(10,file=rnxfilen,form='formatted',status='old',err=10)
      go to 11
   10 continue
      print*,' '
      print*,' Error when trying to open file: ',rnxfilen
      print*,' File is missing or garbled.'
      print*,' '
      print*,' !!!!! JOB ABANDONED !!!!!'
      stop
   11 continue
C
      if(stat.eq.'scratch') then
      open(20,form='formatted',status='scratch')
      elseif(stat.eq.'unknown') then
      open(20,file=rnx3fileout,form='formatted',status='unknown')
      endif
C
      nhead = 0
C
      write(0,'(" Processing input file ",a12)') rnxfilen
      nrec = 0
C
C Copying the header of the input RINEX 3 file to the RINEX 2 version:
C
      kp2 = 0
      kc2 = 0
      kl2 = 0
      klc2= 0
      lp2 = 0
      lc2 = 0
      ll2 = 0
      llc2= 0
   20 continue
      if(ihead.eq.1) then
      nrec = nrec+1
      read(10,'(a80)',end=70) headrec
C!!!
c     print*,headrec
C!!!
      if(nrec.eq.1) then
      if(headrec(61:80).ne.'RINEX VERSION / TYPE') then
      print*,' '
      print*,' File: ',rnxfilen
      print*,' is not a RINEX file, or else the header is garbled.'
      print*,' Hint: First record should have "RINEX VERSION / TYPE"'
      print*,' in columns 61 - 73, but this one does not.'
      print*,' '
      print*,' !!!! JOB ABANDONED !!!!'
      print*,' '
      stop
      endif
      if(headrec(6:6).ne.'3') then
      print*,' File: ',rnxfilen,' is not RINEX V 3'
      print*,' '
      print*,' !!!!! JOB ABANDONED !!!!!!'
      print*,' '
      stop
      endif
      headrec(41:52) = 'G           '
      write(20,'(a80)') headrec
      write(20,'(a20,"RINEX VERSION OF ORIGINAL FILE",10x,"COMMENT",
     ."             ")')
     .headrec(1:20)
      go to 20
      endif
      if(headrec(61:67).eq.'GLONASS') go to 20
cG    7 C1C L1C C1W C2W L2W C2L L2L                          SYS / # / OBS TYPES 
      if(headrec(1:1).ne.'G'.and.headrec(61:79).eq.
     .'SYS / # / OBS TYPES') then
      go to 20
      elseif(headrec(1:1).eq.'G'.and.headrec(61:79).eq.
     .'SYS / # / OBS TYPES'.and.ihead.eq.1) then
      read(headrec(5:6),'(i2)') ntypes
      do i = 1,200
      typestring(i:i) = ' '
      enddo
      write(20,'(a80)') headrec
      typestring(1:52) = headrec(8:60)
      if(ntypes.gt.13) then
      nrec = nrec+1
      read(10,'(a80)',end=70) headrec
      write(20,'(a80)') headrec
      typestring(53:104) = headrec(8:60)
      endif
C!!!
c      print*,ntypes
c      print*,typestring
C!!!
      ks1 = 0
      ks2 = 0
      ksl1 = 0
      do i = 1,ntypes
      k1 = 1+4*(i-1)
      k2 = k1+3
      char4 = typestring(k1:k2)
      if(char4.eq.'C2M '.or.char4.eq.'C2P '.or.char4.eq.'C2W '.
     .or.char4.eq.'C2Y ') then
      kp2 = 1
      lp2 = 4+(i-1)*16
      endif
      if(char4.eq.'C2L '.or.char4.eq.'C2S '.or.char4.eq.'C2X ') then
      kc2 = 1
      lc2 = 4+(i-1)*16
      endif
      if(char4.eq.'L2L '.or.char4.eq.'L2S '.or.char4.eq.'L2X ') then
      klc2 = 1
      llc2 = 4+(i-1)*16
      endif
      if(char4.eq.'L2M '.or.char4.eq.'L2P '.or.char4.eq.'L2W '.
     .or.char4.eq.'L2Y ') then
      kl2 = 1
      endif
      if(char4.eq.'S1C ') ks1 = ks1+1
      if(char4.eq.'S1X ') ks1 = ks1+1
      if(char4.eq.'S1W ') ks1 = ks1+1
      if(char4.eq.'S1P ') ks1 = ks1+1
      if(char4.eq.'S1Y ') ks1 = ks1+1
      if(char4.eq.'S1M ') ks1 = ks1+1
C
      if(char4.eq.'S2C ') ks2 = ks2+1
      if(char4.eq.'S2X ') ks2 = ks2+1
      if(char4.eq.'S2W ') ks2 = ks2+1
      if(char4.eq.'S2P ') ks2 = ks2+1
      if(char4.eq.'S2Y ') ks2 = ks2+1
      if(char4.eq.'S2M ') ks2 = ks2+1
C
      if(char4.eq.'L1C '.or.char4.eq.'L1W '.or.char4.eq.'L1X '.or.
     .char4.eq.'L1P '.or.char4.eq.'L1Y ') ksl1 = ksl1+1
      
C!!!
c     write(*,'(" ks2, char4 "i1,a4)') ks2,char4
C!!!
      enddo
cc      endif
      if(klc2.eq.1.and.l2cmust.eq.2.and.ks2.eq.2) ks2 = 0
      if(kikiriki.eq.0) then
      if(ks1.gt.1.or.ks2.gt.1.or.ksl1.gt.1) then
      print*,' '
      print*,' More than one s/n "S"  column for L1 or L2 data '
      print*,' and more than one phase for L1, according to '
      print*,' the RINEX 3 file header.'
      print*,' To convert to RINEX 2,11, only one such column '
      print*,' can be present for L1''s phase, only one for the s/n '
      print*,' of the pair L1+P1, and one for the s/n of L2+P2.'
      print*,' Chose one type of L1 phase, or of s/n signal, '
      print*,' by changing the first letter in the identifier '
      print*,' of the other phase or s/n data types to a "T" '
      print*,' in the "SYS / # / OBS TYPES" header record. '
      print*,' '
      print*,' !!!!!!! JOB ABANDONED !!!!!!!'
      print*,' '
      stop
      endif
      endif
      go to 20 !!
      endif    !!
      nhead = nhead+1
      write(20,'(a80)') headrec
   12 continue
      if(headrec(61:68).eq.'INTERVAL') interval = 1
      if(nhead.gt.200.and.iendheader.eq.0) then
      print*,' '
      print*,' The input Rinex 3 file: ',rnxfilen
      print*,' does not have an END OF HEADER record.'
      print*,' Insert one manuallly, and run again.'
      print*,' '
      print*,' !!!!!! JOB ABANDONED !!!!!!!'
      print*,' '
      stop
      endif
      if(headrec(61:73).eq.'END OF HEADER') then
      if(interval.eq.0) then
      print*,' '
      print*,' The Rinex 3 file: ',rnxfilen
      print*,' does not have an INTERVAL record in its header.'
      print*,' Insert one manuallly, and run again.'
      print*,' '
      print*,' !!!!!! JOB ABANDONED !!!!!!!'
      print*,' '
      stop
      endif
      iendheader = 1
      ihead = 0
      go to 21
      endif
      endif
      go to 20
   21 continue    
C 
C Read in all data records, copying the GPS records
C to the GPS-only RINEX 3 file.
C
      kprod = kp2*kc2*klc2
      nrecs = 0
      ngps1 = 1
      ntypchars = ntypes*16+3
   50 continue 
     nrec = nrec+1
      read(10,'(a450)',err=22,end=70) datarec
      go to 23
   22 continue
      print*,' '
      print*,' Error occurred while reading record No. ',nrec+1
      print*,' in file ',rnxfilen
      print*,' '
      print*,' !!!!!! JOB ABANDONED !!!!!!'
      print*,' '
      stop     
   23 continue 
      nrec = nrec+1
      if(datarec(1:1).eq.'>') then ! This is the header of a data block.
      write(rnxhead,'(a80)') datarec
c> 2011 08 29 11 00  0.0000000  0 20
      read(rnxhead(31:32),'(i2)') iflag
      if(iflag.gt.1) then      ! Copy as they are "event" records and comments.
      read(rnxhead(34:35),'(i2)') npass
      do i = 2,npass
      nrec = nrec+1
      read(10,'(a80)',err=22) datarec
      write(20,'(a80)') datarec
      enddo
      go to 50
      else
      nrecs = nrecs+1
      read(rnxhead,'(12x,2i3)') ihh,min
      read(rnxhead(34:35),'(i2)') ndata
      endif
      ngps = 0
      do i = 1,ndata
      nrec = nrec+1
      read(10,'(a450)',end=70,err=22) datarec
      if(datarec(1:1).eq.'G') then
      nrecs = nrecs+1 ! Counting the total number of records with GPS data.
      ngps = ngps+1    ! Counting the GPS records in this data block.
      datarecs(ngps) = datarec
C
C If there are records with both P2 and C2, set flag to "0" 
C (no L2 phase and carrier swaps in sub. "cnvrnx3to2": 
C     
C!!!
c     print*,' kprod, kp2, kc2, klc2 ',kprod,kp2,kc2,klc2
c     print*,' kp2, kc2, lp2, lc2 ',kp2,kc2,lp2,lc2
c     if(datarecs(ngps)(lc2:lc2+8).ne.'         ') 
c    .datarecs(ngps)(lp2:lp2+8) = '         '
C!!!
      if(kprod.ne.0) then
      if(datarecs(ngps)(llc2:llc2+8).ne.'         ') then
      read(datarecs(ngps)(2:3),'(i2)') mmprn
      mnot = 0
      do k = 1,32
      if(mmprn.eq.nprnc2(k)) mnot = 1
      enddo
      if(mnot.eq.0) then
      nl2cprn = nl2cprn+1
      nprnc2(nl2cprn) = mmprn
      endif
      endif 
      if(datarecs(ngps)(lp2:lp2+8).ne.'         '.and.
     .   datarecs(ngps)(lc2:lc2+8).ne.'         ')       then
      l2conly = 0
      if(datarecs(ngps)(llc2:llc2+8).ne.'         ') then
      nol2c = 0
      endif
      endif
      endif
C
      endif
      enddo
      write(20,'(a33,i2)') rnxhead(1:33),ngps ! Writing the block header
C                                        in the GPS-only RINEX 3 file.
C
C Writing the GPS data records to the GPS-only RINEX 3 file,
C each with the minimum number of characters (no trailing blanks):
C
      do i = 1,ngps
      do k = 1,450
      datarec(k:k) = ' '
      enddo
      datarec = datarecs(i)
      nchars = 0
      do k = 450,1,-1
      if(datarec(k:k).ne.' ') then
      nchars = k
      go to 80
      endif
      enddo
   80 continue
      do im = 1,450
      if(im.le.nchars) then
      record(im:im) = datarec(im:im)
      elseif(im.le.ntypchars) then
      record(im:im) = ' '
      endif
      enddo
      write(20,'(450a1)') (record(ji:ji),ji=1,ntypchars)
      enddo
      endif
      go to 50
   70 continue
      if(nrec.eq.0) then
      print*,' File: ',rnxfilen,' is empty.'
      print*,' '
      print*,' !!!!!!! JOB ABANDONED !!!!!!!'
      print*,' '
      stop
      endif
  200 continue
C
C!!!
c     print*,' nol2c, l2conly, kl2, ',nol2c,l2conly,kl2
C!!!
      if(nol2c.eq.1) l2conly = 0 ! Do not replace "heritage" L2 Phase
C              with L2C phase when L2C phase is all blanks or is absent.
      if(kl2.eq.0)   l2conly = 1 ! If there is no "heritage" L2 phase,
C                                  replace it with the L2C phase, if possible.
C
      if(l2cmust.eq.1) l2conly = -1 ! Signal to sub. "cnvrnx3to2" that the L2C 
C                                     phase is to be used whenever the L2C code
C                                     is available and there are L2C phase data
C                                     in the RINEX 3 file.
C
      if(l2cmust.eq.2.and.klc2.eq.1) l2conly = 2 ! If both the "heritage" L2 phase 
C                                and the L2C phase are present along with their
C                                corresponding "S2s" put them in separate columns
C                                in the output RINEX 2.11 file.
C
      if(l2cnot.eq.1) then ! User has set "cicreate = -0", to get a rinex 2 file
      l2conly = 0          ! with neither LC2 code nor phase in it.
      endif
C
C!!!
c     l2conly = 1
c     print*,' klc2, l2cmust, l2conly ',klc2,l2cmust,l2conly
C!!!
C
C Now write an output RINEX 2 file with the information 
C in the version 3 output file, but only copy data of C1, P2, L1, L2(P2), and C2
C data types, chosen according to the instructions in this program's header.
C
      irnx2out = 30
      irnx3out = 20
C
      if(charmin.ne.'3') then
      call cnvrnx3to2(rnx3fileout,rnx2fileout,irnx3out,irnx2out,
     .l2conly,rnxfilen,nprnc2,nl2cprn,l2cnot)
      endif
C
      write(0,'(" ")')
      if(iabs(icreate).eq.2.or.(charmin.eq.'3'.and.icreate.eq.0)) then
      write(0,'(" Output rinex 3.01 file: ",a21," has been created.")') 
     .rnx3fileout
      endif
      if(charmin.ne.'3') then
      write(0,'(" Output rinex 2.11 file: ",a21," has been created.")') 
     .rnx2fileout
      endif
      if(icreate.lt.0) then
      write(0,'(" ")')
      write(0,'(" All RINEX 2.11 records for IIR-M, II-F satellites, "
     .)')
      write(0,'(" or later, have the phase of L2C, at user''s ",
     ."request.")')
      endif
      write(0,'(" ")')
      write(0,'(" JOB HAS ENDED")')
      write(0,'(" ")')
C
      stop
      end
C
      subroutine cnvrnx3to2(rnx3fileout,rnx2fileout,irnx3out,irnx2out,
     .l2conly,rnxfilen,nprnc2,nl2cprn,l2cnot)
C
C This subroutine creates a version 2.11 RINEX file from a version 3.01,
C ***GPS-only**** file with: C1, P1, L1(C1 or P1), C2(L, S, or X),
C P2(P, W, or Y), L2(P, W, or Y).
C This file has data from the new civilian type C2, L2 "S", "L", and "X"
C signals from the IIR-M, IIF and later satellites, when these are present.
C Format of a RINEX 3 data record: (a3,[ntypes]f16.5), where "ntypes" 
C is the number of data types of interest.
C (For RINEX 2 records, the format is: ([ntype]*f16.5).)
C
C
C No L5 data are copied to the output RINEX 2 file.
C
C The user has to select which rinex 3 data types are going to be
C copied to the rinex 2 file by "commenting out" the type of all unwanted
C rinex 3 data, in the header of their file, changing the name of the type 
C to "T1 ", "T2 ". Example: C2M = T2  (3 characters, the last one a blank).
C There has to be, at most, only one type of data left unchanged in the header
C for each of basic type groups "C1", "P1", "P2",  "L1", "L2", and "C2",
C and the respective phases and codes have to be truly present (i.e., with both
C listed in the header, and data columns that are not all blanks
C -- but see also comments at the beginning of the main program.
C Due to uncertainty with the treatment by receiver manufacturers 
C
C of the 1/4 cycle offset between the old and the new civilian L2 phase data,
C at least for now, it is safest to choose the "heritage" L2 phase, if
C available, and not the L2 of L2C. (but see also the comments at beginning
C of the main program).
C
C If the user choses the option "+0" in the command line, both the "heritage" 
C L2 phase (as "LC") and the L2C phase are saved in the output RINEX 2.11 file.
C
C
C Input variables: 
C        rnx3fileout = string with the name of the input file.
C        irnx3out    = unit number of input file
C        irnx2out    = unit number of output file
C        l2conly    = flag: = 1 if there are satellites with only L2C data;
C                           = 0 if there is "heritage" L2 phase available.
C                           =-1 if there is only L2C phase available from 
C                                  Block IIR-M, IIF, or only the L2C data is to be copied.
C                           = 2 if there are both L2C and L2 "heritage" phase,
C                                  and both are to be copied.
C                           =-2 as in -1, but a RINEX 3 file with only GPS data
C                                  is created as well.
C Output:
C        rnx2fileout = string with the name of the output file.
C
C     ********************* Oscar L. Colombo - October 2011 *********************
C
      implicit real*8(a-h,o-z)
C
      character*1000 recordin,records(60),typstring
      character*80  recordout,recordo,recordar,recordon
      character*162 stringtyp
      character*21  rnx2fileout
      character*16  rnx3fileout,dataint,dataout(30),blank16
      character*12  rnxfilen      
      character*4   char4,ortyp(28),orbtypec5,orbtypel5,orbtypes5
      character*1   charg
C
      dimension itypes2(30),mprn(32),nchars(110),nprnc2(32)

      data itypes2/30*0/,charg/'G'/,blank16/'         '/,
     .ortyp/28*'    '/
C
      rewind irnx3out
      open(irnx2out,file=rnx2fileout,form='formatted',status='unknown')
C
C Read and copy or convert each header record to its rinex 2 equivalent 
C (e.g. "sys / # /obs types").
C If there is no equivalent, the rinex 3 record is ignored, except for
C the "SYS / PHASE SHIFTS  " record. 
C If a necessary rinex 2 record has no good equivalent in rinex 3,
C that rinex 2 line is created and written in the rinex 2 header 
C (e.g. "wavelength factor").
C
      nrec = 0
      nrecout = 0
      read(irnx3out,'(a80)') recordin
      nrec = 1
      recordin(6:9) = '2.11'
      recordin(41:41) = 'G'
      write(irnx2out,'(a80)') recordin
      nrecout = 1
   10 continue
      read(irnx3out,'(a80)') recordin
      nrec = nrec+1
cG    7 C1C L1C C1W C2W L2W C2L L2L                          SYS / # / OBS TYPES 
      if(recordin(1:1).eq.'G'.and.recordin(61:79).eq.
     .'SYS / # / OBS TYPES') then
      read(recordin(5:6),'(i2)') ntypes
      typstring(1:52) = recordin(8:59)
      read(irnx3out,'(a80)') recordin
      nrec = nrec+1
      if(recordin(1:1).eq.' '.and.recordin(61:79).eq. ! Found a second "OBS TYPE" record.
     .'SYS / # / OBS TYPES') then
      typstring (53:105) = recordin(8:60)      
      else
      backspace irnx3out
      endif
      ntyp = 0
      ntym = 0
      is2 = 0
C
C Setting up a table of pointers (in arrays "stringtyp" and "itypes2"
C to assign a place in the rinex 2 version for the rinex 3 data.
C The user has to select which rinex 3 data types are going to be
C copied to the rinex 2 file by changing the type of all not wanted
C rinex 3 data as "T1 ", "T2 ", or "D1 ", "D2 ". (See comments in the header
C for more information.)
C
      lcidata = 0 ! Block III "L1 signals present" flag.
      lc5data = 0 ! "L5 signals present" flag.
      ic1 = 0
      il1 = 0
      ip1 = 0
      ip2 = 0
      ipp2= 0
      il2 = 0
      ill2= 0
      ic2 = 0
      icc2= 0
      il2c= 0
      iw1 = 0
      is1 = 0
      is2 = 0
      l21 = 0
      kl2c= 0
      is2c= 0
      moretyp = 0
      ic5 = 0
      il5 = 0
      is5 = 0
      lc52= 0
      ll52= 0
      ls52= 0
      do i = 1,162
      stringtyp(i:i) = ' '
      enddo
      do i = 1,ntypes
      i1 = (i-1)*4+1
      i2 = i1+4
      char4 = typstring(i1:i2)
      if(char4.eq.'C1C ') then
      stringtyp(1:6)   = '    C1' ! Eventually, L1C (GPS III) will be available
C      in some satellite but not in others, so it should be treated same as L2C.
      itypes2(i) = 1
      ntyp = ntyp+1
      ntym = ntym+1
      ortyp(itypes2(i)) = char4
      ic1 = 1
      endif
      if(char4.eq.'L1C '.or.char4.eq.'L1P '.or.char4.eq.'L1W '.
     .or.char4.eq.'L1Y '.or.char4.eq.'L1M ') then
      stringtyp(7:12)  = '    L1'
      itypes2(i) = 2
      ntyp = ntyp+1
      ntym = ntym+1
      ortyp(itypes2(i)) = char4
      il1 = 1
      endif
      if(char4.eq.'C2M '.or.char4.eq.'C2P '.or.char4.eq.'C2W '.
     .or.char4.eq.'C2Y ') then
      stringtyp(13:18) = '    P2'
      itypes2(i) = 3
      ntyp = ntyp+1
      ntym = ntym+1
      ortyp(itypes2(i)) = char4
      lp21 = 4+(i-1)*16
      lp22 = lp21+16-1
      ip2 = 1
      endif
      if(char4.eq.'L2M '.or.char4.eq.'L2P '.or.char4.eq.'L2W '.or.
     .char4.eq.'L2Y ') then
      stringtyp(19:24) = '    L2'
      itypes2(i) = 4
      ntyp = ntyp+1
      ntym = ntym+1
      ortyp(itypes2(i)) = char4
      il2 = 1
      endif
      if(char4.eq.'L2S '.or.char4.eq.'L2L '.or.char4.eq.'L2X ') then
      kl2c = 1
      kml2c = kl2c
      if(l2cnot.eq.0.and.(l2conly.ne.0.or.l2conly.eq.2)) then
      l21 = 4+(i-1)*16
      l22 = l21+16-1
      ortyp(9) = char4
      il2c = 1
      iii = i
      endif
      endif
      if(char4.eq.'C2L '.or.char4.eq.'C2S '.or.char4.eq.'C2X ') then
      if(l2cnot.eq.0) then
      itypes2(i) = 5
      stringtyp(25:30) = '    C2'
      lc21 = 4+(i-1)*16
      lc22 = lc21+16-1
      else
      stringtyp(25:30) = '    T2'
      endif
      ntyp = ntyp+1
      ntym = ntym+1
      itypes2(i) = 5
      ortyp(itypes2(i)) = char4
      lc21 = 4+(i-1)*16
      lc22 = lc21+16-1
      ic2 = i
      endif
      if(char4.eq.'C5I '.or.char4.eq.'L5I '.or.char4.eq.'S5I '.or.
     .char4.eq.'C5Q '.or.char4.eq.'L5Q '.or.char4.eq.'S5Q '.or.
     .char4.eq.'C5X '.or.char4.eq.'L5X '.or.char4.eq.'S5X ') then
      l5data = 1
      moretyp = 1
      if(char4(1:2).eq.'C5') then
      lc51 = 4+(i-1)*16
      lc52 = lc51+16-1
      ic5 = i
      orbtypec5 = char4
      endif
      if(char4(1:2).eq.'L5') then
      orbtypel5 = char4
      ll51 = 4+(i-1)*16
      ll52 = ll51+16-1
      il5 = i
      endif
      if(char4(1:2).eq.'S5') then
      orbtypes5 = char4
      ls51 = 4+(i-1)*16
      ls52 = ls51+16-1
      is5 = i
      endif
      endif
      if(char4.eq.'S1C '.or.char4.eq.'S1M '.or.char4.eq.'S1P '.or.
     .char4.eq.'S1Y '.or.char4.eq.'S1W ') then
      stringtyp(31:36) = '    S1'
      itypes2(i) = 6
      ntyp = ntyp+1
      ntym = ntym+1
      ortyp(itypes2(i)) = char4
      is1 = 1
      endif
      if(char4.eq.'S2M '.or.char4.eq.'S2P '.or.char4.eq.'S2W '.or.
     .char4.eq.'S2Y ') then
      is2 = 1   ! S1 and S2 are always together.
      stringtyp(37:42) = '    S2'
      itypes2(i) = 7
      ntyp = ntyp+1
      ntym = ntym+1
      ortyp(itypes2(i)) = char4
      endif
      if(l2cnot.eq.0)then
      if(char4.eq.'S2L '.or.char4.eq.'S2S '.or.char4.eq.'S2X ') then
      is2 = 1   ! S1 and S2 are always together.
      ls1 = 4+(i-1)*16
      ls2 = ls1+16-1
      is2c= 1
      jjj = i
      ortyp(10) = char4
      endif
      endif
C!!!
c      print*,' l2conly, i ',l2conly,i
c      stop
C!!!
      enddo
      if(l2conly.eq.-1) ortyp(10) = '    '
      do i = 1,ntypes
      i1 = (i-1)*4+1
      i2 = i1+4
      char4 = typstring(i1:i2)
      if(char4.eq.'C1M '.or.char4.eq.'C1P '.or.char4.eq.'C1W '.
     .or.char4.eq.'C1Y ') then
      ip1 = 1
      if(ic1.eq.1) then
      if(is2.eq.1) then
      stringtyp(43:48)   = '    P1'
      itypes2(i) = 8
      else
      stringtyp(31:36)   = '    P1'
      itypes2(i) = 6
      endif
      elseif(ic1.eq.0) then
      stringtyp(1:6)     = '    P1'
      itypes2(i) = 1
      endif
      ntyp = ntyp+1
      iw1 = 1
      ntym = ntym+1
      ortyp(itypes2(i)) = char4
      endif
      enddo
C!!!
c      print*,' l2conly,il2c,l2cnot ',l2conly,il2c,l2cnot
C!!!
      if(l2conly.eq.2.and.il2c.eq.1.and.l2cnot.eq.0) then
C!!!
c      print*,' is2, ic1, ip1, is2c ',is2,ic1,ip1,is2c
C!!!
      ntyp = ntyp+1  !!
      if(is2.eq.1.and.ic1.eq.1) then
      if(ip1.eq.1) then
      stringtyp(49:54) = '    LC'
      itypes2(iii) = 9
      if(is2c.eq.1) then   ! <<<<<<
      stringtyp(55:60) = '    SC'
      itypes2(jjj) = 10
      endif
      elseif(ip1.eq.0) then
      stringtyp(43:48) = '    LC'
      itypes2(iii) = 8
      if(is2c.eq.1) then
      stringtyp(49:54) = '    SC'
      itypes2(jjj) = 9
      endif
      endif
      elseif(is2.eq.1.and.ic1.eq.0) then
      if(ip1.eq.1) then
      stringtyp(43:48) = '    LC'
      itypes2(iii) = 8
      if(is2c.eq.1) then   ! <<<<<<
      stringtyp(49:54) = '    SC'
      itypes2(jjj) = 9
      endif
      elseif(ip1.eq.0) then
      stringtyp(37:42) = '    LC'
      itypes2(iii) = 7
      if(is2c.eq.1) then   ! <<<<<<
      stringtyp(43:48) = '    SC'
      itypes2(jjj) = 8
      endif
      endif
      elseif(is2.eq.0.and.ic1.eq.1) then
      if(ip1.eq.1) then
      stringtyp(37:42) = '    LC'
      itypes2(iii) = 7
      if(is2c.eq.1) then   ! <<<<<<
      stringtyp(43:48) = '    SC'
      itypes2(jjj) = 8
      endif
      elseif(ip1.eq.0) then
      stringtyp(31:36) = '    LC'
      itypes2(iii) = 6
      if(is2c.eq.1) then   ! <<<<<<
      stringtyp(37:42) = '    SC'
      itypes2(jjj) = 7
      endif
      endif
      elseif(is2.eq.0.and.ic1.eq.0) then
      if(ip1.eq.1) then
      stringtyp(31:36) = '    LC' 
      itypes2(iii) = 6
      if(is2c.eq.1) then   ! <<<<<<
      stringtyp(37:42) = '    SC'
      itypes2(jjj) = 7
      endif
      elseif(ip1.eq.0) then
      stringtyp(25:30) = '    LC'
      itypes2(iii) = 5
      if(is2c.eq.1) then   ! <<<<<<
      stringtyp(31:36) = '    SC'
      itypes2(jjj) = 6
      endif
      endif
      endif
      if(l2cnot.eq.0) then
      if(itypes2(iii).lt.9) then
      ortyp(itypes2(iii)) = ortyp(9)
      ortyp(itypes2(iii)+1) = ortyp(10)
      if(itypes2(iii).lt.8) then
      ortyp(9)  = '    '
      ortyp(10) = '    '
      elseif(itypes2(iii).eq.8) then
      ortyp(10) = '   '
      endif
      endif
      if(is2c.eq.1) ntyp = ntyp+1
C!!!
c      print*,' ntyp ',ntyp
c      print*,stringtyp
C!!!
      elseif(l2cnot.eq.1) then
      ortyp(9)  = '    '
      ortyp(10) = '    '
      endif
      endif
C
C Checking for missing essential data types, reserving their spaces for blank columns:
C
      if(ip2.eq.0) then ! There has to be a "P2" column, even a blank one.
      stringtyp(13:18) = '    P2'
      ntyp = ntyp+1
      ntym = ntym+1
      lp21 = 0
      ipp2= 1
      write(recordout,'(
     ."+ P2: No P2 in RINEX 3 file: blank column has been created. ",
     ."COMMENT")')
      nrecout = nrecout+1
      write(irnx2out,'(a80)') recordout
      endif
      if(ic2.eq.0.or.l2cnot.eq.1) then ! There has to be a "C2" column, even a blank one.
      if(l2cnot.eq.0) then
      stringtyp(25:30) = '    C2'
      write(recordout,'(
     ."+C2: No C2 in RINEX 3 file: blank column has been created.  ",
     ."COMMENT")')
      nrecout = nrecout+1
      write(irnx2out,'(a80)') recordout
      ntyp = ntyp+1
      ntym = ntym+1
      elseif(l2cnot.eq.1) then 
      stringtyp(25:30) = '    T2'
      write(recordout,'("+C2: No C2 in RINEX 3 copied, blank ""T2""",
     ." column put instead.COMMENT")')
      write(irnx2out,'(a80)') recordout
      nrecout = nrecout+1
      endif
      lc21 = 0
      icc2= 1
      endif
      if(il2.eq.0) then ! There has to be an "L2" column, even a blank one.
C                         (and once all satellites are Block IIR-M, IIF, or III)
      stringtyp(19:24) = '    L2'
      ntyp = ntyp+1
      ntym = ntym+1
      ll21 = 0
      ilc2 = 1
      write(recordout,'(
     ."+ L2: No L2 in RINEX 3: L2C phase saved as L2, when possible",
     .". COMMENT")')
      write(irnx2out,'(a80)') recordout
      nrecout = nrecout+1
      endif
      igout = 0
      if(l2conly.eq.-1.and.il2c.eq.0.or.il2.eq.0) then
      print*,' No phase of either L2 or L2C declared in header,'
      print*,' but the use of both phases is requested by user.'
      igout = 1
      endif
      if(l2conly.eq.-1.and.il2c.eq.0) then
      print*,' There is no phase of L2C declared in header,'
      print*,' but the use of L2C phase is requested by user.'
      igout = 1
      endif
      if(l2conly.eq.-1.and.ic2.eq.0) then
      print*,' There is no C2 declared in header,'
      print*,' and the use of L2C phase is requested by user.'
      igout = 1
      endif
      if(l2conly.eq.2.and.(il2c.eq.0.or.il2.eq.0)) then
      print*,' There is either no "heritage" L2 phase or no L2C phase,'
      print*,' but user has asked to have both in the RINEX 2 file.'
      endif
      if(ic1.eq.0.and.iw1.eq.0) then
      print*,' There is no C1 or P1 declared in header.'
      igout = 1
      endif
      if(il1.eq.0) then
      print*,' There is no L1 declared in header.'
      igout = 1
      endif
      if(ip2.eq.0.and.ic2.eq.0) then
      print*,' There is no P2 or C2 declared in header.'
      igout = 1
      endif
      if(il2.eq.0.and.il2c.eq.0) then
      print*,' No "heritage" L2 or L2C''s L2 declared in header.'
      igout = 1
      endif
      if(is1.ne.is2) then
      print*,' One of S1, S2 is declared in header,'
      print*,' but not the other.'
      igout = 1
      endif
      if(igout.eq.1) go to 123
      go to 124
  123 continue
      print*,' '
      print*,' In the header of the RINEX 3 file: ',rnxfilen
      print*,' one or more essential or required data types '
      print*,' are missing, so this file cannot be processed:'
      print*,' '
      print*,' !!!!!!! JOB ABANDONED !!!!!!!'
      print*,' '
      stop
  124 continue
C
      IF(moretyp.eq.1) THEN
C!!!
c     print*,' moretyp ',moretyp
c     print*,' itypes2 ',itypes2
c     print*,' ic5, il5, is5 ',ic5,il5,is5
C!!!
      do i = 1,ntypes
      if(itypes2(i).ne.0) ntypmax = i
      enddo
      if(l5data.eq.1) then ! There are L5 data, so copy them to the Rinex 2 version.
      ntyp = ntypmax
      if(ic5.gt.0) then
      ntyp = ntyp+1
      itypes2(ic5) = ntyp
      ortyp(ntyp) = orbtypec5
      stringtyp((ntyp-1)*6+1:(ntyp*6)) = '    C5'
      endif
      if(il5.gt.0) then
      ntyp = ntyp+1
      itypes2(il5) = ntyp
      ortyp(ntyp) = orbtypel5
      stringtyp((ntyp-1)*6+1:(ntyp*6)) = '    L5'
      endif
      if(is5.gt.0) then
      ntyp = ntyp+1
      itypes2(is5) = ntyp
      ortyp(ntyp) = orbtypes5
      stringtyp((ntyp-1)*6+1:(ntyp*6)) = '    S5'
      endif
      endif
      if(lcidata.eq.1) then ! There are Block III LC1 data, so copy them to the Rinex 2 version.
      ntyp = ntyp+1
      if(l5data.eq.0) ntyp = ntypmax+1
C...
      endif
C!!!
c     print*,' ntyp ',ntyp,' ntypes ',ntypes
c     print*,' itypes2 ',itypes2
C!!!
      endif ! If(moretyp.eq.1) THEN...
C
c     8    C1    C2    P1    P2    L1    L2    S1    S2      # / TYPES OF OBSERV
      if(stringtyp((ntyp-1)*6+1:ntyp*6).eq.'      ') ntyp = ntyp-1
      if(ntyp.le.9) then
      write(irnx2out,'(4x,i2,a54,"# / TYPES OF OBSERV ")') 
     .ntyp,stringtyp(1:54)
      nrecout = nrecout+1
      elseif(ntyp.le.18) then
      write(irnx2out,'(4x,i2,a54,"# / TYPES OF OBSERV ")') 
     .ntyp,stringtyp(1:54)
      nrecout = nrecout+1
      write(irnx2out,'(6x,a54,"# / TYPES OF OBSERV ")') 
     .stringtyp(55:108)
      nrecout = nrecout+1
      if(ntyp.gt.18) then
      write(irnx2out,'(6x,a54,"# / TYPES OF OBSERV ")') 
     .stringtyp(109:162)
      nrecout = nrecout+1
      endif
      endif
      write(irnx2out,'("NO DOPPLER DATA COPIED FROM THE ",
     ."RINEX 3 FILE.               COMMENT             ")')
      write(irnx2out,'("DATA TYPES COPIED FROM THE ORIGINAL RINEX ",
     ."3 FILE:           COMMENT             ")')
      nrecout = nrecout+1
      do j = 1,80
      recordo(j:j) = ' '
      enddo
      if(ntyp.le.14) then
      write(recordo,'("@ ",14a4)') (ortyp(k),k=1,14)
      write(recordo(61:67),'("COMMENT")')
      write(irnx2out,'(a80)') recordo
      nrecout = nrecout+1
      else
      write(recordo,'("@ ",14a4)') (ortyp(k),k=1,14)
      write(recordo(61:67),'("COMMENT")')
      write(irnx2out,'(a80)') recordo
      nrecout = nrecout+1
      write(recordo,'("@ ",14a4)') (ortyp(k),k=15,28)
      write(recordo(61:67),'("COMMENT")')
      write(irnx2out,'(a80)') recordo
      nrecout = nrecout+1
      endif
      go to 10
      endif
      if(recordin(61:79).eq.'SYS / # / OBS TYPES') go to 10
      if(recordin(61:78).eq.'SYS / PHASE SHIFTS') then
      if(recordin(1:3).eq.'G L'.and.recordin(6:10).eq.'-25') then
      go to 10
      else
      kml2c = 0
      if(recordin(1:11).eq.'G L2L -0.25') then
      write(recordin(1:80),
     .'("G L2L -0.25000                                              ",
     ."COMMENT")') 
      endif
      if(l2conly.eq.0) then
      if(l2cnot.eq.0) then
      write(irnx2out,'(a80)') recordin
      nrecout = nrecout+1
      write(recordin(1:80),
     .'("All L2 phase in this file is ""heritage"" (but see below). ",
     ."   COMMENT")')
      if(l21.ne.0) then
      write(irnx2out,'(a80)') recordin
      nrecout = nrecout+1
      write(recordin(1:80),
     .'("The L2C phase copied only to replace any blank L2 entries. ",
     ." COMMENT")')
      else
      write(irnx2out,'(a80)') recordin
      nrecout = nrecout+1
      write(recordin(1:80),
     .'("No L2C phase replaced any blank L2 phase entries",
     ."            COMMENT")')
      endif
      endif
      if(l2cnot.eq.1) then
      write(irnx2out,'(a80)') recordin
      nrecout = nrecout+1
      write(recordin(1:80),
     .'("NO L2C data in the original file was copied to this file.   ",
     ."COMMENT")')      
      endif
      elseif(l2conly.eq.1) then
      write(irnx2out,'(a80)') recordin
      nrecout = nrecout+1
      write(recordin(1:80),
     .'("For IIR-M, IIF: If only L2C phase available: saved as ""L2""",
     .". COMMENT")')
      elseif(l2conly.eq.-1) then
      write(irnx2out,'(a80)') recordin
      nrecout = nrecout+1
      write(recordin(1:80),
     .'("For IIR-M, IIF: If L2 and L2C phase present: only L2C ",
     ."phase COMMENT")')
      write(irnx2out,'(a80)') recordin
      nrecout = nrecout+1
      write(recordin(1:80),
     .'("saved in column ""L2"".                                    ",
     ."   COMMENT")')
      elseif(l2conly.eq.2) then
      write(irnx2out,'(a80)') recordin
      nrecout = nrecout+1
      write(recordin(1:80),
     .'("For IIR-M, IIF: both heritage L2 phase and L2C phase saved.",
     ." COMMENT")')
      write(irnx2out,'(a80)') recordin
      nrecout = nrecout+1
      write(recordin(1:80),
     .'("(""LC"" is the L2C phase, ""SC"" is the L2C S/N) ",
     ."               COMMENT")')
      endif
      if(l2conly.ne.2) then
      if(l2cnot.eq.0) then
      if(l2conly.eq.-1) then
      write(recordin(1:80),
     .'("The ""heritage"" L2 has been replaced with the phase of L2C.",
     ."  COMMENT")')
      else
      write(recordin(1:80),
     .'("NO ""heritage"" L2 has been replaced with the phase of L2C. ",
     ."  COMMENT")')
      endif
      elseif(l2cnot.eq.1) then
      write(recordin(1:80),
     .'("NO L2C data in the original file was copied to this file.   ",
     ."COMMENT")')      
      endif
      endif
      endif
      endif
C
      if(recordin(61:73).eq.'END OF HEADER'.and.nl2cprn.ne.0) then
      write(recordon,'("%     Number L2C satellites: ",i2,
     .", listed below by PRN:",7x,"COMMENT")') nl2cprn
      write(irnx2out,'(a80)') recordon
      do km = 1,80
      recordon(km:km) = ' '
      enddo
      nsss = nl2cprn
      if(nl2cprn.gt.18) nsss = 18
      write(recordon,'("%   ",18(" ",i2))') (nprnc2(km),
     .km=1,nsss)     
      recordon(61:67) = 'COMMENT'
      write(irnx2out,'(a80)') recordon
      if(nl2cprn.gt.18) then
      do km = 1,80
      recordon(km:km) = ' '
      enddo
      write(recordon,'("%   ",18(" ",i2))') (nprnc2(km),
     .km=19,nl2cprn)     
      recordon(61:67) = 'COMMENT'
      write(irnx2out,'(a80)') recordon
      endif
      endif
C
      if(recordin(61:73).eq.'END OF HEADER'.and.kml2c.ne.0) then
      recordar = recordin
C
      write(recordin(1:80),
     .'("G% NO 1/4 CYCLE CORRECTION APPLIED TO THE L2C PHASE.      ",
     ,"  COMMENT")')
      if(l2conly.eq.0) then
      write(irnx2out,'(a80)') recordin
      nrecout = nrecout+1
      write(recordin(1:80),
     .'("All L2 phase in this file is ""heritage"" (but see below). ",
     ."   COMMENT")')
      if(l21.ne.0) then
      write(irnx2out,'(a80)') recordin
      nrecout = nrecout+1
      write(recordin(1:80),
     .'("The L2C phase copied only to replace any blank L2 entries. ",
     ." COMMENT")')
      else
      write(irnx2out,'(a80)') recordin
      nrecout = nrecout+1
      write(recordin(1:80),
     .'("No L2C phase replaced any blank L2 phase entries",
     ."            COMMENT")')
      endif
      elseif(l2conly.eq.1) then
      write(irnx2out,'(a80)') recordin
      nrecout = nrecout+1
      write(recordin(1:80),
     .'("For IIR-M, IIF: If only L2C phase available: saved as ""L2""",
     .". COMMENT")')
      elseif(l2conly.eq.-1) then
      write(irnx2out,'(a80)') recordin
      nrecout = nrecout+1
      write(recordin(1:80),
     .'("For IIR-M, IIF: If L2 and L2C phase present: only L2C ",
     ."phase COMMENT")')
      write(irnx2out,'(a80)') recordin
      nrecout = nrecout+1
      write(recordin(1:80),
     .'("saved in column ""L2"".                                    ",
     ."   COMMENT")')
      elseif(l2conly.eq.2) then
      write(irnx2out,'(a80)') recordin
      nrecout = nrecout+1
      write(recordin(1:80),
     .'("For IIR-M, IIF: both heritage L2 phase and L2C phase saved.",
     ." COMMENT")')
      write(irnx2out,'(a80)') recordin
      nrecout = nrecout+1
      write(recordin(1:80),
     .'("(""LC"" is the L2C phase, ""SC"" is the L2C S/N) ",
     ."               COMMENT")')
      endif
      write(irnx2out,'(a80)') recordin
      nrecout = nrecout+1
      if(l2conly.ne.2) then
      if(l2cnot.eq.0) then
      if(l2conly.eq.-1) then
      write(recordin(1:80),
     .'("The ""heritage"" L2 has been replaced with the phase of L2C.",
     ."  COMMENT")')
      else
      write(recordin(1:80),
     .'("NO ""heritage"" L2 has been replaced with the phase of L2C. ",
     ."  COMMENT")')
      endif
      elseif(l2cnot.eq.1) then
      write(recordin(1:80),
     .'("NO L2C data in the original file was copied to this file.   ",
     ."COMMENT")')      
      endif
      write(irnx2out,'(a80)') recordin
      nrecout = nrecout+1
      endif
      go to 11
      endif
C
c     1     1                                                WAVELENGTH FACT L1/2
      if(recordin(61:68).eq.'ANTENNA:') then
      write(irnx2out,'(5x,"1     1",48x,"WAVELENGTH FACT L1/2")')
      endif
      nrecout = nrecout+1
      if(recordin(61:73).eq.'END OF HEADER') then
      recordar = recordin
      go to 11
      endif
      write(irnx2out,'(a80)') recordin
      nrecout = nrecout+1
      go to 10
   11 continue
      write(irnx2out,'(a80)') recordar
      nrecout = nrecout+1
  100 continue
      read(irnx3out,'(a450)',end=200) recordin
      nrec = nrec+1
      if(recordin(1:1).eq.'>') then ! Creating in memory, and then
C                           writing to the output file a 
C                           rinex 2-formatted data block,
C                           with the epoch, etc. in its first record,
C                           followed by as many data records 
C                           as there are GPS satellites.
C!!!
c     print*,' ntyp ',ntyp
C!!!
c> 2011 08 29 01 00  0.0000000  0 10                                                                             
c 11 07 10 13 11 30.0000000  0 10G18G 8G29G25G 6G22G31G 3G15G21         
      write(records(1),'(1x,a31)') recordin(5:35)
      read(records(1)(31:32),'(i2)') nsats ! "nsats" is the number of GPS
C                                                            data records.
C!!!
c     print*,' records(1) ',records(1)
c     print*,' nsats ',nsats
C!!!
      ip = 1
      do i = 1,nsats ! Creating the observation records in array "records".
      ip = ip+1     
      read(irnx3out,'(a450)',end=200) recordin
      nrec = nrec+1
      read(recordin(2:4),'(i2)') nprn
      mprn(i) = nprn
      do j = 1,ntyp
      dataout(j) = blank16
      enddo
      do k = 1,ntypes ! "ntypes" is the number of data types listed
C                        in the rinex 3 header.
      k1 = 4+(k-1)*16
      k2 = k1+16
      dataint = recordin(k1:k2)
      imm = itypes2(k)
      if(imm.ne.0) then
      dataout(imm) = dataint
      if(imm.eq.5.and.l2cnot.eq.1.and.l2conly.eq.0) 
     .dataout(imm) = blank16
      if(l2conly.eq.1.and.lc21.ne.0) then ! In data records with L2C only, 
C                   replace the L2 and S2 blanks with the corresponding
C                   L2C values.
      if(recordin(lc21:lc22).ne.blank16) then
      if(lp21.ne.0)                             then
      if(recordin(lp21:lp22).
     .eq.blank16) then ! If this record is for one of those satellites, proceed.
      if(imm.eq.4) dataout(imm) = recordin(l21:l22)
      if(imm.eq.7.and.recordin(k1:k2).eq.blank16) 
     .dataout(imm) = recordin(ls1:ls2)
      endif
      endif
      endif
      endif
      endif
      enddo
      if(il2.eq.0.and.l2conly.eq.1) dataout(4) = recordin(l21:l22) ! When the
C            "heritage" signals are not present, use the L2C phase, if the L2C
C             code and phase are available.
      if(l2conly.eq.-1.and.lc21.ne.0.and.l21.ne.0) then
      if(recordin(lc21:lc22).ne.blank16) then
      dataout(4) = recordin(l21:l22) ! When the user requires the use of 
C                                      the L2C phase in all obs. of satellites
C                                      of blocks IIR-M, IIF and later ones 
C                                      -- if available in the RINEX 3 file. 
C
      endif
      endif
      if(ntyp.le.5) then  ! "ntyp" is the number of data types
C                            listed in the output rinex 2 file.
      write(records(ip),'(5a16)') (dataout(ik),ik=1,ntyp)
      nchars(ip) = ntyp*16
      else
      write(records(ip),'(5a16)') (dataout(ik),ik=1,5)
      nchars(ip) = 80
C
      nkkk = ntyp/5
      if((ntyp/5)*5.eq.ntyp) nkkk = nkkk-1
      do j = 1,nkkk
      lim1 = j*5+1
      lim2 = lim1+4
      if(lim2.gt.ntyp) lim2 = ntyp
      ip = ip+1
      nchars(ip) = 80
      write(records(ip),'(5a16)') 
     .                       (dataout(ik),ik=lim1,lim2)
      do k = 80,1,-1
      km = k
      if(records(ip)(k:k).ne.' ') then
      go to 90
      endif
      enddo
   90 continue
      if(lim2.eq.ntyp) km = 16*(lim2-lim1+1)
      nchars(ip) = km
      enddo
      endif
      enddo
C
      ntoto = 33+nsats*3-1
      write(records(1)(33:80),'(20(a1,i2))') (charg,mprn(i),i=1,nsats) ! Creating the header
C                                                    of the rinex 2 block in array "records".
      if(nsats.le.12) then
      write(irnx2out,'(80a1)') (records(1)(k:k),k=1,ntoto) ! Writing the block header record to the output rinex 2 file.
      else
      write(irnx2out,'(80a1)') (records(1)(k:k),k=1,68) ! Writing the block header record to the output rinex 2 file.
      write(irnx2out,'(32x,47a1)') (records(1)(k:k),k=69,33+ntoto)
      endif
      do i = 2,ip
      write(irnx2out,'(80a1)') (records(i)(k:k),k=1,nchars(i))
      enddo
      endif
      go to 100
C
  200 continue
C
      return
      end
C