Engineering Drawing Segmentation

Project overview

Architectural and building-services drawings were segmented so that room extents, service routes and annotation blocks could be lifted from a flat CAD export into structured data.

Drawings are an unusual annotation target. There is no texture or colour to separate classes, only line weight, hatch pattern and symbol convention, and a single sheet can carry several overlapping layers of information at once.

Work performed

• Read each sheet's legend before annotating so symbols were interpreted against the drawing's own convention.
• Traced room boundaries along the internal wall face rather than the centreline.
• Followed service routes through the sheet, including where they cross other line work.
• Boxed equipment symbols and dimension callouts as separate classes.
• Kept hatched and filled areas distinct from the regions they overlay.
• Reconciled ambiguous line work against the title block and revision notes.

What made it hard

• Class separation rests on line weight and hatch pattern rather than colour or texture.
• Service routes cross wall runs and dimension lines at the same pixel.
• Symbol conventions differ between sheets from different practices.
• Dense annotation zones leave very little clear space between elements.
• Scanned and re-exported sheets carry compression artefacts along thin lines.
• Room boundaries are implied by wall geometry rather than drawn as a closed shape.

Result

A drawing segmentation set that lets downstream tooling recover room extents and service layouts from flat sheets, with layered information kept separate rather than flattened together.

Final deliverable

Delivered per-sheet polygon and box annotations with a consistent class scheme, checked against each drawing's legend and title block.