Images and scans to DWG — paper drawings redrawn, and revised while they are redrawn

What this covers

Raster material of every quality: flatbed scans of paper prints, phone photographs taken at an angle under bad light, faxes of faxes, TIFF archives from a scanning bureau, and mixed sets where half the sheets are one and half the other. No vector data exists in any of it, so nothing can be measured off the file. Every dimension has to come from what is written on the sheet, and every gap in that has to be reasoned about.

That reasoning is the service. Automatic raster-to-vector tracing exists and it is cheap, and it produces a mesh of jagged polylines that follows the noise in the scan as faithfully as it follows the walls. It cannot tell a dimension line from a wall, a stain from a hatch, or a fold in the paper from a partition. We draw the sheet as a drawing, deciding what each mark on it was meant to be.

Changes made in the same pass

Most clients do not send a scan because they want that exact drawing again. They send it because the building is about to change and the old sheet is the only record of what is there. So the redraw and the revision happen together, in one job rather than two:

• Openings moved, added or closed up, partitions revised, rooms merged or split
• Dimension chains rebuilt and restated, room numbering and areas recalculated
• Existing and proposed shown separately, with demolition and new work distinguished as your practice does it
• Missing sheets reconstructed, a section or an elevation that the archive lost, drawn from the plans that survived
• Composite sheets split into separate drawings, or several sheets combined into one
• Your title block, layer standard, text styles and drawing numbering applied throughout

Where a requested change conflicts with something in the source, a wall you want moved that a section shows as loadbearing, or a dimension that no longer adds up once an opening shifts, we raise it before drawing rather than afterwards.

How scale is established

Never from the pixels. Scale comes from the dimension chain written on the sheet, checked against a second chain elsewhere on the same drawing. On old prints the two often disagree, because paper shrinks unevenly and every generation of copying drifts, and a drawing scanned at an angle is not even internally consistent. Where the written dimensions run out, geometry is interpolated and the interpolation is listed in the note rather than hidden inside apparently precise linework.

Accuracy and what it depends on

A redrawn file is only as good as what it was redrawn from. From a clean scan with a full dimension chain, the result is as accurate as the original draughtsman was. From a photograph of a faded print with no dimensions at all, you get a proportionally correct drawing and a plain statement that it is not survey-grade. If what the project actually needs is a measured survey of the building, we will say so rather than sell a file that looks precise and is not.

Can you work from a photograph rather than a scan?

Yes. Photographs of prints, including ones taken at an angle or in poor light, are normal input. What limits the result is not the photograph but whether the drawing carries written dimensions, because that is what the geometry is built from.

Why not just use automatic raster-to-vector tracing?

Tracing follows the noise in the scan as faithfully as it follows the walls, and it cannot distinguish a dimension line from a partition or a stain from a hatch. What comes out is a mesh of polylines, not a drawing anyone can draft on.

Can you change the drawing while redrawing it?

Yes, and it is usually the reason the work is commissioned. Openings moved or closed, partitions revised, dimensions and room numbering restated, existing and proposed separated. A marked-up print, a sketch or a written list is enough to work from.

What if the scan has no dimensions written on it at all?

Then you get a proportionally correct drawing and a written statement that it is not survey-grade. We will also tell you if a measured survey is what the project actually needs, rather than delivering a file that looks precise and is not.

Can you handle a mixed archive of scans and vector PDFs?

Yes. Mixed sets are normal and you do not need to sort them first. Working out which sheet supersedes which is part of the job, and the sheets are priced according to what each one actually is.