I have a GIS with a logistics layer that contains line features. The lines have been digitised from aerial photography and each line represents a path from A to B, following roads, rail and waterways.

My goal is to write the real world distance along each path to a column within the attribute table.

So far I have tried using:

[Toolbox > Vector geometry > Add geometry attributes] Add Geometry Attributes

The results are as follows: Results

My result of 16.5 is confusing, because the actual distance in this case is about 1650km. I followed a tutorial to do this and their results were in metres, so I guess my questions are:

  1. Is my result in degrees or some other units?
  2. Is there a better way to get the ellipsoidal distance along each line into the attribute table?

(Edited to note I am using QGIS 3.10)

  • 1
    Area & length calculation in QGIS cares about the layer CRS. And your layer is in EPSG 4326 - thus, your results are in degree. Try to find a CRS fitting your AOI which is based on m. – Erik Jan 28 at 10:16

Under "Project Properties > General"

Set the ellipsoid to WGS84 and units to km. enter image description here

Then use "Attribute Table > Field Calculator" enter image description here

The $length function can then be used to update a distance column correctly as it respects the current project's ellipsoid and distance unit settings.

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