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Surface QC

Audits a TIN surface for drainage and data problems: computes each triangle's max slope from its plane normal, flags flat triangles (ponding / flat spots) and spike triangles (bad survey points), and reports surface stats.

Command VDCSURFQC · VDC QC tab › Design QC panel
Audits a TIN surface for drainage and data problems: computes each triangle's max slope from its plane normal, flags flat triangles (ponding / flat spots) and spike triangles (bad survey points), and reports surface stats.
TIN triangles: max slope < 0.5% = FLAT (warn); slope > 50% & relief > 5' = SPIKE (error). FLAT 0.2% max slope < FlatSlopePct → ponding SPIKE relief > 5' slope > SteepSlopePct AND relief > SpikeReliefFt → bad point Surface stats Triangles: 8,214 Elev: 28.10 – 41.55 2D area: 6.42 ac
TIN triangle (passing)   Flat, WARNING   Spike, ERROR   Surface stats

What it does, per run

  • Pick: surface dropdown lists every TIN surface in the drawing; set thresholds in the dialog.
  • Slope: reads the triangles and computes each triangle's max slope from its plane normal.
  • Flat: max slope below FlatSlopePct (default 0.5%), potential ponding, reported WARNING at the centroid.
  • Spike: slope over SteepSlopePct (default 50%, ~2:1) and relief over SpikeReliefFt (default 5 ft), ERROR (both required so graded slopes pass).
  • Stats: reports triangle count, min/max elevation, and 2D area.

Outputs & settings

  • <drawing> - Surface QC.csv plus the findings palette; double-click a row to zoom to the triangle.
  • Each check capped at MaxReportedPerCheck rows, with a summary line when the cap is hit.
  • Settings: VDC_SURFQC_SETTINGS, default %APPDATA%\VDC\SurfaceQc\settings.json, schema-tolerant.
  • Holds the surface name, the flat/spike thresholds, the per-check cap, and the two check toggles.
  • Legit flat areas (ponds, parking, detention bottoms) will flag, tune FlatSlopePct or toggle the flat check off.

Dialog

Surface QC dialog
Surface QC, VDCSURFQC

When to use it

  • Sanity-checking a survey or proposed surface for ponding flats and bad-point spikes before using it.

How to run it

  1. Run VDCSURFQC and pick the TIN surface from the dropdown.
  2. Set the flat / spike thresholds (or accept the defaults) and click OK.
  3. Review the surface stats on the command line and the flat/spike findings in the palette; double-click a finding to zoom to it.

Options

  • Flat triangles: flagged when the triangle slope is below the flat threshold (default 0.5%).
  • Spikes: flagged when the slope is above the spike threshold (default 50%) AND the vertical relief is over the limit (default 5 ft).

Watch out for

  • If the surface is renamed after settings are saved, the tool reports it 'not found' - re-run and re-pick.
  • The CSV is only written when the drawing is saved to a real path; an unsaved drawing gets palette output only.

Related: ADA Slope · Road QC · QC Status