10-FOOT PORTABLE SUBTENSE BAR

THE SUBTENSE BAR HAS LONG BEEN ACCEPTED THEORETICALLY AS A BASE FOR TRIANGULATION. WHEN USED WITH PRECISE SURVEY INSTRUMENTS, VERY ACCURATE RESULTS CAN BE OBTAINED. IN RECOGNITION OF THE POTENTIAL OF THIS DEVICE, EUROPEANS HAVE DESIGNED AND USED SUBTENSE BARS FOR MANY YEARS. THEIR SUBTENSE BARS, AT LEAST THOSE USED COMMERCIALLY IN THIS COUNTRY, ARE LIMITED TO A 2-METER LENGTH. IT WAS REASONED THAT COMPUTATIONS WOULD BE SIMPLIFIED AND THE RANGE OF OPERATIONS WOULD BE PROPORTIONATELY INCREASED IF THE BAR LENGTH COULD BE INCREASED TO 10 FT. TO RETAIN ITS VALUE FOR FIELD USE, 10 FT WAS ARBITRARILY SELECTED AS THE OPTIMUM FOR PORTABILITY AND WIND RESISTANCE. A WORKING MODEL HAS ANSWERED ALL THE REQUIREMENTS OF PORTABILITY AND ACCURACY. TO HOLD THE COST TO A MINIMUM, THE BASIC PARTS OF THE INSTRUMENT WERE CONSTRUCTED FROM OBSOLETE SURVEYING INSTRUMENTS. A GRADUATED CENTERING ROD WAS INCORPORATED SO THE EXACT HEIGHT OF INSTRUMENT COULD BE EASILY DETERMINED. ALTHOUGH THE PRIMARY PURPOSE OF THE SUBTENSE BAR IS FOR HORIZONTAL TRAVERSE, IT WAS REASONED THAT IT WOULD ALSO BE VALUABLE FOR TRIGONOMETRIC LEVELING. /AUTHOR/

Media Info

  • Monograph Title: Photogrammetry - developments and applications: 1958
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00202706
  • Record Type: Publication
  • Files: TRIS, TRB
  • Created Date: Sep 16 1994 12:00AM