- The plan table forces a translation step: from drawing, to memory, to tape measure, to layout — and every translation leaks accuracy.
- AR overlay eliminates the translation by registering the model to the physical space and rendering it in place.
- The hard problems are registration (anchoring model to reality), drift (holding alignment as the wearer moves), and occlusion (drawing the model behind real objects).
- Useful field overlay needs construction-grade precision against the BIM record — visualization-grade 'close enough' creates rework instead of preventing it.
The plan table is a translation problem
Every plan table — wood or tablet — imposes the same workflow: read the drawing over there, hold it in your head, walk over here, and reproduce it with a tape and a chalk line. Drawing to memory, memory to measurement, measurement to layout. Three translations, and every one of them leaks.
AR blueprint overlay deletes the translations. Register the model to the space, render the wall where the wall goes, and the layout stops being a reproduction of the drawing — it is the drawing, at full scale, in place.
The three hard problems
Making that real on a construction site — not a demo floor — comes down to three engineering problems:
- Registration: anchoring the model to the physical space. The system has to find correspondences between what the cameras and depth sensors see and the BIM geometry, and it has to survive a site that changes daily.
- Drift: holding alignment while the wearer moves. Head-mounted tracking accumulates error; without continuous re-alignment against the model, an overlay that started perfect is lying within minutes.
- Occlusion: drawing the model behind reality. If projected ductwork renders in front of an installed column, the brain rejects the whole image. Depth-correct occlusion is what makes an overlay readable as 'in the room.'
Why precision is the whole game
There's a version of AR overlay that's fine for marketing videos and useless for layout — the 'roughly there' hologram. Construction doesn't have a use for roughly. If the overlay can't hold tight alignment against the BIM record set while the wearer walks, it can't be trusted for the one thing the field needs it for: telling you whether what's built matches what's designed.
That bar is what we hold Corevis to: continuous capture fused with the model, alignment checked in a tight loop rather than set-and-forget, and drift surfaced honestly instead of hidden. The overlay is an instrument, not an effect.
The plan table had a 500-year run. It earned retirement. What replaces it isn't a screen — it's the drawing standing in the room, holding still, telling the truth.
“The overlay is an instrument, not an effect. Construction has no use for 'roughly there.'”