AutoCAD Tip: Legacy Scan-to-CAD Workflow for AutoCAD

Converting legacy scans to clean, editable CAD is straightforward when you apply a disciplined workflow and the right tools.

Pick the right approach:

• Use the AutoCAD Raster Design toolset for semi-automatic vectorization, raster cleanup, OCR, and rubber-sheeting. If you don’t have it, check licensing options at NOVEDGE.
• For noisy or low-quality scans, manual tracing in AutoCAD often produces better geometry than full auto-vectorization.

Prepare the image before vectorizing:

• Scan at 300–600 dpi for linework; use 400+ dpi for fine text or detailed drawings.
• Convert to bitonal (black/white) for linework when possible; use grayscale only if you must preserve halftones.
• Clean the raster: deskew, crop excess borders, despeckle, and thicken faint lines. These steps drastically improve vector recognition.
• Name the file consistently and store it with your DWG. Consider a standards-based folder structure to keep projects organized.

Attach and calibrate in AutoCAD:

• Attach the image and place it on a dedicated “Rasters” layer with plotting turned off.
• Calibrate scale using known distances: align two or more control points, then rotate/scale so the image matches drawing units.
• Set a light transparency (e.g., 40–60%) to make tracing and QA easier, and use image clipping to hide irrelevant areas.

Vectorization strategies:

• Semi-automatic: with Raster Design, use line/arc/polyline recognition tools with corner/arc sensitivity tuned to your scan. Favor polylines with arc segments for cleaner results.
• Manual tracing: draw with polylines, arcs, and splines; enable object snaps and polar tracking. Keep each discipline on its own layer for quick visibility control.
• Fit arcs to curves rather than using many short segments; simplify where appropriate.

Text and symbols:

• Try OCR for clear, consistent fonts; verify results with spellcheck and a standards-compliant text style.
• For repeat symbols, replace raster marks with blocks. This improves consistency and supports data extraction later.

Quality control and cleanup:

• Overlay check: toggle the raster on/off to compare your vectors against the scan at multiple zoom levels.
• Use Overkill to remove duplicates and PEDIT to join small segments where needed.
• Verify critical dimensions with Measure tools; adjust scale if accumulated error appears.

Deliverable polish:

• Purge unused content, audit the file, and standardize layers, linetypes, and plot styles.
• Store the original scan with the DWG for traceability, and document assumptions made during interpretation.

Need the right toolset for this workflow? Explore AutoCAD and the Raster Design toolset options at NOVEDGE—their team can help you choose the most cost-effective configuration for your environment.