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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. We traditionally design and build accurately at each cross-section

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Automated Machine Guidance: Electronic Files and Design Data

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  1. Automated Machine Guidance: Electronic Files and Design Data AASHTO Subcommittee on Construction Meeting August 18, 2010 – Burlington, VT Mark Taylor

  2. 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

  3. Design Today: Cross Section- Based 3D Design Modeling

  4. 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)

  5. 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

  6. Electronic File Formats • ASCII (generic software) • Land XML (Topcon software) • Trimble (Trimble Terramodel and Sitevision software) • Trimble .TTM format

  7. Pattern Lines for 3D Design Model

  8. 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

  9. Chords Between Sections

  10. 3D Design Model Tolerances

  11. Rec’d Pattern Line Spacing *Also at centerline points (PC, PT etc.) and at superelevation and widening transitions for final design

  12. Cross-Sections for 3D Design Model

  13. Template Surface Points Subgrade Layer

  14. Connect Similar Cross-Section Point Labels Using Breaklines

  15. Transitions (Cut to Fill)

  16. Cut to Fill Breaklines

  17. 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)

  18. 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

  19. 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

  20. 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)

  21. 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

  22. 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

  23. 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

  24. 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?

  25. Caution: Automated Computer Design Plus Machine Guidance

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