04_ScriptsA4 - Migrate Survey Data from Legacy Drawing

A4 - Migrate Survey Data from Legacy Drawing

A4 - Migrate Survey Data from Legacy Drawing

Script Family

Series A - Data Exchange

Purpose

Extracts survey data from supported legacy DGN drawings converted to DWG and attached as XREFs.

When to Use

Use A4 when migrating survey data from Bentley MicroStation legacy drawings into a Civil 3D workflow. It is not intended for extracting information from Civil 3D drawings themselves.

Inputs

  • Legacy DGN file opened and exported to DWG from Bentley MicroStation.
  • Pre-processed DWG attached to the target Civil 3D drawing as an XREF.
  • External Reference selection.
  • Proximity Tolerance.

Outputs

  • Recognised Point Features as COGO Points with Point Codes in Raw Description.
  • Recognised Linear Features as colour-coded linework with Linetypes set by detected Feature Code.
  • Unrecognised Linear Features, typically with Point Code XX assigned.
  • Fragmented Linear Features needing manual review.

Workflow Summary

  1. Open the legacy DGN file in Bentley MicroStation.
  2. Export it as a DWG using the manual-defined export settings.
  3. Pre-process the exported DWG in Civil 3D by detaching XREFs, running OVERKILL, and setting drawing units to metres.
  4. Attach the prepared DWG as an XREF in the target drawing.
  5. Run A4 with an appropriate Proximity Tolerance.
  6. Review output classes and perform manual corrections.
  7. Use A1b_Plot_Survey_Data_From_Drawing_Selection to convert the reviewed data into styled Civil 3D objects.

Legacy DGN exported to DWG. This is not a point data file format.

Reverse-Engineering Notes

When reverse-engineering this Dynamo graph, identify:

  • How XREF contents are traversed.
  • How legacy symbols and linework are recognised.
  • How proximity tolerance is applied to close gaps and remove duplicates.
  • How recognised and unrecognised output classes are created.
  • How linetype or Raw Description is used to pass Feature Code information to A1b.

Source Basis

  • Primary source: HAPI User Manual.pdf, Section 2.3.5.
  • This note is a manual-facing script overview, not a PythonNet3 implementation specification.

Open Questions

  • Confirm which legacy symbol libraries and linetype mappings are encoded in the Dynamo graph.
  • Confirm whether A4 should remain a pre-processing tool rather than direct Civil 3D object creation.
Built with LogoFlowershow