Merge individual RINEX navigation files into a single file 
 
 USAGE: sh_merge_nav -t YYYY DDD [-c eph_ID] [-p path] [-d] 
 
 where 
 
  -t 4-digit year, day-of-year, e.g. 2000 035  (required)  
  -c ephemerid ID  [default = brdc]           (optional)  
  -p path(s) where individual compressed or uncmpressed nav files stored, default pwd
  -d run dos to unix on the input rinex nav files  [default no]