Implementing Digital Terrain Models (DTM) for Construction Plans and Determining Earthwork Quantities

Quarterly Reports Other Documents Final Report
Research Brief Final Report

Primary Investigator

Awad Hanna
Construction and Materials Support Center
University of Wisconsin – Madison
1415 Engineering Drive, 2314 EH
Madison, WI 53706
hanna@engr.wisc.edu

Abstract

Use of Global Positioning System (GPS) technology to guide and control earth moving equipment such as dozers, motor graders, and excavators is quickly becoming common place in highway construction because it speeds project delivery and cuts costs.  It has been estimated that productivity of this type equipment is double that of conventional equipment.  A requirement for use of GPS technology in machine guidance is a 3D terrain model known as a digital terrain model (DTM).  Current design practice is to design highways and other infrastructure facilities in two-dimensions using traditional computerized design programs.  GPS machine guidance technology requires that these designs then be converted to three-dimensional (3D) representations before they can be used.  This conversion is currently being done by the construction contractor which adds time, cost, and introduces a source of error into the system.  To leverage the advantages of the technology throughout project delivery, the design phase must produce the DTM.

The Wisconsin Department of Transportation (WisDOT) is in the process of implementing new 3D design software which will accomplish this task.  However, there are numerous cultural, legal, and work process questions which must be answered before WisDOT begins to distribute DTM’s as contractual documents, eliminates traditional cross sections, uses them as a basis for determining final quantities, and allows contractors to construct directly from them.  These are not trivial issues.  For example, only one State highway agency currently claims to be using agency produced DTM’s for these purposes.   The issues and agency/industry ramifications must be carefully identified and studied before making the policy changes needed for implementation of DTM’s in this capacity.

Objectives

To assist WisDOT in the preliminary stages of identifying the relevant design and construction work process that would be impacted, the consequences, and the legal issues that could arise by directly providing agency produced DTM’s to contractors for contractual purposes.  Results of this project will assist WisDOT in getting full utilization of their new 3D design software and facilitate the current progress of implementing GPS machine controlled grading.

Tasks

  1. Develop questionnaire and distribute to AASHTO TIG group
  2. Investigate current use of cross sections within WisDOT
  3. Develop comparisons of DTM-to-DTM versus average-end-area for volume computations
  4. Analyze responses to questionnaire and perform follow up
  5. Interim report
  6. Obtain feedback from WisDOT regions, industry, and consultants
  7. Final report

Project Information

  • Duration: 8 months
  • Dates: December 15, 2008 – August 15, 2009
  • Budget: $18,925
  • Modal Orientation: Highway
  • Project ID: CFIRE 02-11
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