Understand · Everyday · 4 min
Scale and accuracy: where a length comes from
A measurement is points on the sheet times a scale you set. Understanding that tells you how far to trust it.
Every length DatoMark reports is worked out the same way: the distance between the points you clicked, measured on the sheet, multiplied by the scale for that page. Nothing else goes into it. That’s why a take-off can be reproduced, and why it is only as good as two things: where you clicked, and the scale you set.
Where you click
Snapping puts points on the drawing's own corners and line ends, which removes most of the error. On a sheet with no lines to snap to (a scan), your accuracy is how closely you can place a point by eye, so zoom in.
The scale
The scale comes from a distance you give it, not from the “1:100” in the title block. A drawing plotted “fit to page”, or one that was shrunk by a photocopier, is no longer at its stated scale, but a printed dimension on it’s still right. So calibrate from a printed dimension, and check against a second one.
Units and rounding
Values are held at full precision and shown rounded to your setting. What you read is tidy, and what a spreadsheet adds up is the actual measurement. Changing the display unit never changes a measurement.
Several scales on one set
Each page has its own scale, because a set is rarely all at one scale. A measurement remembers the scale it was taken under. If you change a page's scale afterwards, the register flags the measurements that were made at the old one and lets you decide what to do.