Does any one know what CRS the QGIS digitizing toolbox (CAD tool) and the measure line tool use?

Because I couldn't find any way to manually set the CRS for the tools in QGIS 3, my assumption is that it will use the CRS set for the QGIS project. But I am seeing inconsistent values of the two tools when setting the project CRS to EPSG 3857 (Pseudo-Mercator). While the CAD tool shows a distance of 5m, the measure line tool only measures a distance of 3.3m.

  • 1
    I'd say the measurement tool was doing you a favor, by indicating how inaccurate notorious Web Mercator is at that location.
    – Vince
    Mar 5, 2019 at 14:03

1 Answer 1


The Advanced Digitizing Panel use the project CRS, and it must be a projected system.

The tools are not enabled if the map view is in geographic coordinates.

If you want to draw a segment of a given length, click the d (distance) text box (keyboard shortcut D), type the distance value (in map units) and press Enter.

The Measuring Tool measures the ellipsoidal length, and the ellipsoid and units can be defined in the project properties.

The default measurement metric is ellipsoidal, using the ellipsoid defined in Project ‣ Properties… ‣ General. This is true both when geographic and projected coordinate systems are defined for the project.

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