In our work, we frequently need to compare floor plan drawings. Often, we have to compare older drawings from archives with very new and detailed ones. The scales of these drawings often differ — sometimes from 1:100 to 1:200, but more commonly with small variations of 1–5% at a detailed level.
Our current workflow is as follows: we create a snapshot of the old drawing and align it with the new one. We then manually stretch the drawing by eye, repeatedly correcting its placement. Afterward, we try to fine-tune the proportions by adjusting the scale in decimal values within the property field.
AutoCAD offers a function to scale with a reference point. With this, you can align both drawings (even at different scales) on a fixed point on the X,Y axis. You then select a base point on the snapshot to be scaled, followed by a reference point (for example, the nearest grid line on the drawing). Finally, you can click the corresponding point on the underlying drawing with your mouse. This works similarly to a "calibrate scale" functionality.
