EXTENDING CONTROL SURVEYS BY PHOTOGRAMMETRY

THE U. S. FOREST SERVICE IS INTERESTED IN IMPROVING ITS METHODS AND TECHNIQUES OF EXTENDING (BRIDGING) HORIZONTAL AND VERTICAL CONTROL SURVEYS BY USE OF PHOTOGRAMMETRY. THE PURPOSE OF THIS PAPER IS TO REPORT THE RESULTS OF A SERIES OF TESTS ON PRODUCTION PROJECTS, CARRIED ON IN COOPERATION WITH THE VIRGINIA DEPARTMENT OF HIGHWAYS. THESE TESTS WERE DIVIDED INTO TWO PHASES: (1) EVALUATING THE EXTENSION OF CONTROL BY ANALOG AND ANALYTIC BRIDGING AND (2) EXPANDING TOPOGRAPHIC MAPPING CONTROL TO HIGHWAY DESIGN PHOTOGRAPHY BY PHOTOGRAMMETRY. TWENTY-FIVE AERIAL PHOTOGRAPHS, AT A SCALE OF 350 FT/IN. , CONTAINING 77 HORIZONTAL AND 210 VERTICAL CONTROL POINTS, WERE USED IN THE FIRST TEST. THIS MATERIAL WAS BRIDGED USING MEASUREMENTS MADE WITH THE ZEISS STEROPLANIGRAPH, MODEL C8, AND THE MANN MONOSCOPIC COMPARATOR, AND EACH BRIDGE WAS COMPUTED WITH IDENTICAL VARYING AMOUNTS OF CONTROL. TWO SCALES OF PHOTOGRAPHY WERE USED IN THE SECOND TEST: 2,000 FT/IN. (USED FOR STANDARD TOPOGRAPHIC MAPPING ON A QUADRANGLE BASIS) AND 500 FT/IN. (USED FOR HIGHWAY DESIGN MAPPING). COMMON IMAGE POINTS WERE SELECTED BETWEEN THE TWO SCALES OF PHOTOGRAPHY, AND THE SMALL-SCALE PHOTOGRAPHY WAS BRIDGED, THEREBY ESTABLISHING X, Y, Z COORDINATES FOR THE COMMON IMAGE POINTS. THE DESIGN PHOTOGRAPHY WAS THEN BRIDGED, USING THE COMMON IMAGE POINTS AS CONTROL. THE STANDARD DEVIATION FOR THE ANALYTICAL BRIDGING, WITH CONTROL EVERY SIXTH MODEL, WAS 0.59 FT HORIZONTALLY AND 0.47 FT VERTICALLY. THE ANALYTIC METHOD SHOWED THAT ERRORS ARE REDUCED ABOUT ONE-THIRD HORIZONTALLY AND ONE-FOURTH VERTICALLY, AS COMPARED TO THE ANALOG METHOD. DESIGN MAPPING CAN BE ACCOMPLISHED, USING HORIZONTAL CONTROL ESTABLISHED FOR THE SMALL-SCALE TOPOGRAPHIC MAPPING, TO AN ACCURACY OF 1:4, 700, BUT A DATUM SHIFT CAN BE EXPECTED. /AUTHOR/

Media Info

  • Media Type: Print
  • Features: References; Tables;
  • Pagination: pp 58-63
  • Monograph Title: Geometric design: photogrammetry and aerial surveys
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00202725
  • Record Type: Publication
  • Files: TRIS, TRB
  • Created Date: Oct 14 1994 12:00AM