Bringing a plan in is three steps: import the image, set its scale, start tracing. The Reference image strip sits above the drawing and stays there whatever you are doing, so the controls are never somewhere you have to go looking for. The image is screen-only and is never printed.
Tracing is free. If you would rather not do it yourself, there is a done-for-you tracing service from €29 a floor.
Getting the image in
Three ways, and they all do the same thing:
- Import image or PDF… in the Reference image strip.
- Drag the file straight onto the canvas — a photo, a scan, a screenshot, a PDF.
- New plan → Trace a plan, which starts a fresh plan around the image.
A PDF with more than one page asks which page you want. If the floor already has a reference image, you are asked before it is replaced — your drawing stays either way, and you can undo it.
Setting the scale
This is the step that makes the trace measurable, and it takes about ten seconds. The panel walks you through it as soon as the image lands:
- Straighten it, if it needs it. A photo taken at a slight angle is easier to mark accurately once it is square. Drag the Rotation slider to find the angle by eye, then nudge it with − and + (a tenth of a degree each) or type an exact value; ⟲ and ⟳ turn a sheet that came in sideways. This is offered before you place the first point, and goes away afterwards — turning the image later would slide the thing you marked out from under the mark.
- Mark a known distance. Click one end of something whose real length you know — a dimension written on the plan, a door opening, a wall you have measured — then click the other end. Zoom and pan as much as you like; the points stay on the image, not on the grid. Longer is better: a 6 m dimension is far more forgiving of a shaky click than a 600 mm one. (No mouse? Place points with the keyboard gives you a crosshair the arrow keys drive — Shift for ten pixels at a time — and Enter places a point.)
- Type the real length.
3500and3.5mboth work, and so do10ftand12'-6". A bare number means whatever unit your plan is in. The panel shows how it read your entry before you apply it, so a slip is visible first. - Apply. The image resizes so everything you trace off it comes out in real millimetres.
Nothing changes in the document until you press Apply, and Apply is a single undo step. If you change your mind mid-way, Do this later or Escape leaves the image exactly as it was.
If the PDF already knows its own scale
Some PDFs carry their dimensions as real text. When one does, Gridsnap reads the plot scale off the drawing and sizes the image straight away — the strip says Scale detected and there is nothing to mark. It is a reading of the drawing rather than a promise about it, so Check scale is there if you want to confirm it against a distance you know.
What the status means
The strip always says where the image’s size came from:
| Status | What it means |
|---|---|
| Scale not set | Just imported. The size on screen is a guess, not a measurement. |
| Scale detected | Read from a PDF’s own dimensions. Check it if you are unsure. |
| Scale set | You marked a distance and typed its real length. |
| Scale unverified | Either an older plan, or the width was typed by hand. Usable, but nothing has been measured. |
Setting the scale again later
Image settings in the strip is open to you at any time — while a wall is selected, while the door tool is armed, whenever. Set scale again is the second thing in it.
One thing worth knowing before you do: changing the scale resizes only the image. Your walls, rooms and dimensions stay exactly where they are and the same size as before, so if you have already drawn over the plan, a rescale will put the two out of alignment. Gridsnap asks you to confirm you understand that before it applies one.
The rest of the image settings
| Control | What it does |
|---|---|
| Opacity | How strongly the image shows through. All the way to zero. |
| See through walls | Fades what you have drawn so the image shows through it — how you find the doors and windows once the walls are traced over the top of them. A view setting: nothing in the document, nothing in the export. |
| Rotation | Slider, −/+ steps of a tenth of a degree, an exact field, and quarter turns. Squares up a scan or a photo taken at a slight angle; it does not correct perspective. |
| Position and size | Move the image, or set its width by hand. Typing a width is a scale change nobody measured, so the status drops to unverified — check a known distance afterwards. |
| Replace image… / Remove image | Swap the image, or take it off this floor. |
Detecting walls (experimental)
Detect walls reads walls drawn as two parallel lines and proposes them for review; you accept the ones it got right and they become ordinary walls in one undoable step. Doors, windows and rooms stay yours to add.
It needs the scale set first — it is reading distances off the image, so without one every wall it proposed would be the wrong size. It also works only on images in a building-sized range; a very large site plan or a very small detail is outside what it can read, and you can still trace those by hand.
What this doesn’t do
- The reference image never prints. It is not on the PDF, the DWG, the DXF or the PNG.
- One image per floor. Trace each storey from its own scan.
- It does not rescale your drawing. Setting the image scale moves the image, never the walls.
Next
Drawing a wall and drawing to an exact length — with the scale set, the numbers you type and the numbers you trace agree.