How to digitize a paper floor plan: scan, scale, trace

To digitize a floor plan is to turn a paper drawing — an old blueprint, a framed evacuation plan, a photocopy from the landlord — into something a computer can use. Spatial Map is a browser-based indoor mapping platform that takes a scanned or photographed plan as an image, places it at real-world scale on a map, and turns it into a multi-floor indoor map with live data. Before you start, decide how far you need to go:

Level 1 is always needed. Levels 2 and 3 are different jobs: you rarely need a CAD redraw just to get an indoor map, and a CAD drawing on its own still is not one.

A scanner gives the best result because the sheet is flat and the optics are square to it. A phone photo works for small plans and for plans you cannot take off the wall.

• Keep the edges. Include all four corners of the sheet in the photo; they are your reference for squaring it.
• Light it evenly. Two light sources at an angle beat one overhead lamp; shadows across the sheet become grey smudges later.
• Hold the camera parallel. Every degree of tilt has to be corrected afterwards, and corrections cost sharpness.
• Save losslessly. Keep the master as PNG or TIFF; JPEG artefacts blur thin lines.

1. 1
   Correct perspective

   Document-scanner apps do this automatically when they detect the page. In an image editor, use the perspective or “warp” tool and pull the four sheet corners to a rectangle with the sheet’s real proportions (an A-size sheet is 1 : 1.414).

2. 2
   Check the right angles

   Long walls should be straight and corners square. Curved lines near the edges mean lens distortion; retake from further away rather than fix it.

3. 3
   Crop and straighten

   Crop to the plan area plus the scale bar, and rotate so the main walls are horizontal.

4. 4
   Clean the background

   Use levels or a threshold to turn yellowed paper white and lines black. Remove stains and folds with a soft eraser, not by redrawing.

5. 5
   Export a working copy

   Keep the master. For map use, export a copy of at most 4096 px on its long edge — larger images do not display on some devices.

A digital image has pixels, not metres. You need one trustworthy real-world length to convert between them — and the written scale on a paper plan is the least trustworthy, because photocopiers and printers quietly enlarge or shrink.

Measure the reference in pixels, divide by its real length, and you know the size of the whole image. For example, a 40 m wall that is 1,600 px long means 40 px per metre, so a 4,000 px-wide image covers 100 m. Check a second dimension in the other direction: if it disagrees, the perspective correction is off.

Automatic raster-to-vector converters exist, and they help with clean drawings. On old, hand-drawn or stained plans they produce many short, broken lines that take longer to fix than to trace. Either way, walk the building: paper plans are often decades behind the walls.

In Spatial Map, upload the cleaned image (PNG, JPEG, GIF or WebP) in the floor plan tool and drag a box on the map to place it. Then type its real Width — with Lock aspect ratio on, the height follows — lower the Opacity, and rotate and nudge it until it sits on the building. The floor plan tool guide covers every control.

Next, let AI Map draft the floor from the image: walls, doors, racks, labels, areas, stairs, lifts and escalators appear on the map for review, and you add them all or kind by kind. The cleaner the scan, the cleaner the draft — which is the practical reward for steps 1 and 2. Fix and add what is missing with the drawing tools, name the rooms, and the plan is now a map. See AI floor plan mapping.

A three-floor building mapped from its plans

If you later receive a better scan or a CAD drawing, Replace image swaps the picture while keeping its position and size, so everything traced on top stays aligned. The full path from any kind of plan is on floor plan to indoor map, and the 7-day free trial covers up to 5 facilities with no card.