NUMERIC GROUND IMAGE SYSTEMS DESIGN

THE NUMERIC GROUND IMAGE (NGI) SYSTEM STUDY IS AN EXAMPLE OF THE SYSTEMS APPROACH TO THE DESIGN OF A COMPUTER SOFTWARE SYSTEM. THE NGI SYSTEM FURNISHES THE HIGHWAY ENGINEER WITH A METHOD FOR APPROXIMATING THE TERRAIN SURFACE WITH A NUMERICAL SURFACE. THE USE OF THIS APPROACH ELIMINATES SOME TERRAIN REPRESENTATION PROBLEMS ASSOCIATED WITH THE TRADITIONAL CROSS-SECTION METHOD. THE NGI APPROACH IS NOT DIRECTLY REFERENCED TO ANY SPECIFIC ALIGNMENT. IT WAS DESIGNED TO INTERFACE WITH FORTRAN DRIVER PROGRAMS. WHENEVER THE INTERFACING PROGRAM REQUIRES AN ELEVATION AT A SPECIFIC HORIZONTAL POSITION, IT PASSES THE X AND Y COORDINATES OF THAT POSITION TO THE NGI SYSTEM THROUGH THE APPROPRIATE INTERFACE. THE NGI SYSTEM COMPUTES THE ELEVATION CORRESPONDING TO THE X AND Y AND PASSES IT BACK TO THE ORIGINAL PROGRAM THROUGH THE SAME INTERFACE. IT COMPUTES THE REQUIRED ELEVATIONS IN THIS MANNER. THE ENSEMBLE OF TERRAIN DATA POINTS ARE DIVIDED INTO RECTANGULAR SECTORS AND THEN STORED BY SECTOR IN A DIRECT ACCESS DEVICE. AS THE SECTOR DATA POINTS ARE REQUIRED FOR ELEVATION COMPUTATIONS, THEY ARE BROUGHT FROM STORAGE INTO THE CORE. THE CLUSTER OF DATA POINTS SURROUNDING THE REQUIRED POINT ARE THEN SELECTED FROM THE SECTOR DATA. THE ELEVATION OF THE DESIRED POINT IS OBTAINED FROM A SURFACE WHICH HAS BEEN FIT BY LEAST SQUARES TO THE CLUSTER OF TERRAIN DATA POINTS. ONCE THE OPERATING CHARACTERISTICS OF THE NGI SYSTEM ARE DETERMINED AND SURFACE TECHNOLOGY IS EXTENDED INTO ENGINEERING DESIGN, IT HOLDS THE PROMISE OF BECOMING A HIGHLY EFFECTIVE HIGHWAY DESIGN TECHNIQUE.

  • Supplemental Notes:
    • Res Rept 120-1, 30 PP, 25 FIG, 20 REF
  • Corporate Authors:

    Texas Transportation Institute

    Texas A&M University System, 1600 E Lamar Boulevard
    Arlington, TX  United States  76011
  • Authors:
    • Maxwell, D A
    • Turpin, R D
  • Publication Date: 1968-8

Subject/Index Terms

Filing Info

  • Accession Number: 00202778
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Sep 2 1994 12:00AM