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 Get RINEX obser/kreizvation files from SOPAC, CDDIS, UNAVCO IGN or BKG archives  
  
 Usage: sh_get_rinex -archive <archive> -yr <yr> -doy <doy> -ndays <num> -sites <sites> -ftp_prog <ftp/ncftp> -list
  
        <archive>  One of the archives specified in ftp_addresses [Default sopac] 
        <yr> 4 char year of nav data requested  [Required] 
        <doy> 3 char day of year of nav data requested [Required] 
        <num> Number of consecutive days of data to retreive [Default 1] 
        <sites> List of sites to be retreived from the ftp archive [Required] 
        <ftp/ncftp> select the ftp program to be used [default ftp]
        <list> get list of available files from selected archive
        <xcheck>    do not ftp rinex data if xfile exists already [defaul N]
  
 Examples: sh_get_rinex -archive sopac -yr 1998 -doy 235 -ndays 1 -sites algo drao ankr 
           sh_get_rinex -archive cddis -yr 1998 -doy 235 -ndays 7 -ftp_prog ncftp
           sh_get_rinex -archive cddis -yr 1998 -doy 235 -ndays 7 -ftp_prog ncftp -xcheck Y
           sh_get_rinex -archive sopac -yr 1998 -doy 235 -list
  
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