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ADA Slope Audit

Samples the proposed surface across closed polygons on the ADA layers: stalls, aisles, landings, and routes, fits a plane to each region, and flags any slope that exceeds the ADAAG limits.

Command VDCADASLOPE · VDC QC tab › Site QC panel
Samples the proposed surface across closed polygons on the ADA layers: stalls, aisles, landings, and routes, fits a plane to each region, and flags any slope that exceeds the ADAAG limits.
Grid-sample each ADA region × fit a least-squares plane × check slope vs. the limit. Proposed surface (sampled at spacing + vertices) STALL 1.6% ≤ 2.0% OK ACCESS AISLE STALL 2.6% > 2.0% ERROR max any-dir gradient LANDING 1.9% ≤ 2.0% OK ACCESSIBLE ROUTE running 4.2% ≤ 5.0% cross 2.4% > 2.0% ERROR split on principal (long) axis
Region within limit   Over-limit (ERROR)   Access aisle polygon   Route (running / cross split)   Grid sample point   Sampled surface

What it does, per run

  • Classify: finds closed polygons on the ADA layers, tags each as stall, aisle, landing, or route.
  • Sample: reads the chosen surface on a grid at the set spacing plus every polygon vertex.
  • Plane fit: least-squares plane over the samples yields the slope gradient, then it is checked.
  • Stalls / aisles / landings: steepest slope in any direction must stay under AnyDirectionMaxPct.
  • Routes: gradient split on the principal (long) axis, RouteRunningMaxPct vs. RouteCrossMaxPct.
  • Thin surface coverage over a region reports a WARNING instead of a pass/fail.

Settings & outputs

  • Limits: any-direction 2.0%; route running 5.0% / cross 2.0% (defaults).
  • Sample spacing: grid interval across each region, default 2 ft.
  • Layers: four editable name lists (stall / aisle / landing / route), must match your annotation or nothing is found.
  • Config: VDC_ADASLOPE_SETTINGS, default %APPDATA%\VDC\AdaSlope\settings.json; schema-tolerant load.
  • Output: <drawing> - ADA Slope.csv plus the findings palette (double-click to zoom).
  • Scope: regions must be closed polygons; bulges read as chords; break L-shaped routes into straight runs.

Dialog

ADA Slope Audit dialog
ADA Slope Audit, VDCADASLOPE

When to use it

  • Checking accessible parking, aisles, landings, and routes for ADA-compliant slopes against the design surface.

How to run it

  1. Draw the ADA regions as closed polygons on the ADA layers (stalls / aisles / landings / routes).
  2. Run VDCADASLOPE, pick the surface, and set the slope limits and sample spacing.
  3. Review the over-limit findings in the palette; double-click a finding to zoom to the region.

Options

  • Stalls / aisles / landings: max 2% in any direction (default).
  • Routes: max 5% running and 2% cross slope (default).
  • Sample spacing: grid interval the surface is sampled at across each region (default 2 ft).

Watch out for

  • The ADA layer lists are edited in settings.json (shown as hints in the dialog) - if your layer names differ, nothing is found.
  • The regions must be CLOSED polygons on the ADA layers; no closed regions means nothing to sample.
  • If the surface is renamed after settings are saved, re-run and re-pick it.

Related: Surface QC · Parking · Road QC