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Automated Machine Guidance: Electronic Files and Design Data . AASHTO Subcommittee on Construction Meeting August 18, 2010 – Burlington, VT Mark Taylor. Cross-Sections vs. Surfaces. We traditionally design and build accurately at each cross-section

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automated machine guidance electronic files and design data

Automated Machine Guidance: Electronic Files and Design Data

AASHTO Subcommittee on Construction Meeting

August 18, 2010 – Burlington, VT

Mark Taylor

cross sections vs surfaces
Cross-Sections vs. Surfaces
  • We traditionally design and build accurately at each cross-section
  • We now have the capability to design and build accurately everywhere
  • However, construction can only be as accurate as the survey data and controls
  • Construction control tolerance is not any more precise than the design 3D surface model
3d design surface layers
3D Design Surface Layers
  • Finished surface (top of pavement)
  • Aggregate base (bottom of pavement) to foreslope
  • Aggregate subbase layers (if any)
  • Subgrade surface from slope stake to slope stake
  • Subexcavation or wall foundations (undercut)
3d design model work flow
3D Design Model Work Flow
  • Develop the geometric design information
  • Prepare cross sections for design model
  • Generate 3D design surface model (TIN)
  • Check the 3D surface tolerances
  • Verify the 3D surface path
  • Spot check xyz of the TIN
  • Clip the existing terrain and merge the design and terrain surface models
  • Export the combined 3D surface models
    • Generate file formats for the Contractor
electronic file formats
Electronic File Formats
  • ASCII (generic software)
  • Land XML (Topcon software)
  • Trimble (Trimble Terramodel and Sitevision software)
    • Trimble .TTM format
pattern lines for 3d model
Pattern Lines for 3D Model
  • Interval spacing is dependent on the radius of curvature
  • Add sections at the beginning and end of superelevation transitions
  • At begin and end of widening transitions, including for traffic barrier terminals
  • At begin and end of road approach intersections
  • Changes in ditch configuration and inlets
rec d pattern line spacing
Rec’d Pattern Line Spacing

*Also at centerline points (PC, PT etc.) and at superelevation and widening transitions for final design

an ideal world
An Ideal World
  • The Design engineer provides the Contractor a complete 3D model that fits site conditions
  • Contractor easily loads 3D surface model directly into the machine guidance system
  • The Contractor builds project accurately to the plans, specifications, and tolerances
  • Any changes or revisions are updated in the 3D surface model by the project engineer
  • As-built 3D surface model is given back to the owner (State DOT)
the real world
The Real World
  • Existing ground data does not match to site conditions or with 3D design surface model
  • Missing data, information and details about exceptions to the model
    • Lack of detail at intersections and culvert inlets and outlets requires manual adjustments and warping
    • Ditch profiles do not match with culvert inlets or site conditions
    • Special ditch information is shown in the plans profile but is not in the 3D design surface model
  • Specifications do not fully address the work
design changes for 3d amg
Design Changes for 3D/AMG
  • Cross section pattern lines at closer intervals (typically 10-feet instead of 50-feet) to achieve the required accuracy in the 3D surface
  • Proficiency with special applications of the design software to generate the 3D surface
  • Time-intensive activities associated with these new applications are:
    • Hand–editing any cross-sections that cannot be drawn with standard criteria (modify text search)
    • QC checks of the 3D surface between pattern lines
changes for 3d amg cont d
Changes for 3D/AMG cont’d
  • Contract special provisions
    • How to resolve discrepancies between the electronic data and the contract plans
    • Responsibility for changes to electronic data
  • Achieving a common understanding of the concepts and limitations in the design model
    • Exceptions (what is not modeled)
    • Degree of accuracy and precision
    • Discontinuities (linear changes and transitions)
construction changes for amg
Construction Changes for AMG
  • Understanding the concepts and limitations of the electronic 3D design model (exceptions, degree of accuracy)
  • Understanding the AMG accuracy limitations
  • Performing the necessary layout, inspection activities with less “wood in the ground”
  • Using suitable survey equipment and methods for layout, inspection activities, and for independent QA of the Contractor’s AMG methods
challenges for 3d design
Challenges for 3D Design
  • Modeling guidance and training is needed
  • Standards for the 3D model deliverables
    • Design data files that are provided
    • Electronic data formats
  • Professional liability/Engineer of record
  • Consistency, uniformity, quality control
  • Quantities calculation and documentation
  • QA/QC of 3D data (DTM, design data files)
  • Field verification and changes to design data
  • Documentation of as-built project features
rrr projects challenges for 3d design modeling
RRR Projects: Challenges for 3D Design Modeling
  • Procedures and specifications for using design models derived from resource-grade survey and mapping technologies
  • Develop end-result, performance based methods and specifications for control, rather than strict line and grade position
  • Allow flexibility and foster innovation
  • Expedite production and reduce costs
standards and procedures
Standards and Procedures
  • When to develop 3D design models for AMG?
  • How to develop the model?
    • What features to include?
    • How many layers?
    • What level of detail?
  • What format to provide the model for others to use?
  • How to manage changes to the as-built design model?
  • How to document and retain electronic records?