I'm currently trying to perform an analysis on a number of points and their EEZ regions in QGIS (see my earlier question here).

Here's an impression of what I've done so far:

enter image description here

In dark red, I've created a dissolved feature of a collection of line buffers around the EEZ regions. In grey, I've dissolved the relevant EEZ regions themselves.

I'd like to compare the areas of both. This is where it's getting strange. When I inspect the area of the buffered borders, it's about 960.412 square kilometers, see:

enter image description here

But when I inspect the area of the EEZs as a whole, it amounts to merely 66.739 square kilometers!

enter image description here

Clearly, the area of the EEZs as a whole should be larger than the area of the buffered EEZ borders (by a few orders of magnitude).

Questions: what's going wrong? And how can I obtain the correct areas of the buffered borders and the EEZ regions as a whole, respectively?

  • 1
    So what CRS are your layers in? Looks like at least one of your layers is in a projected CRS (like EPSG:4326) with units in degrees: so calculating area does not make any sense.
    – Babel
    Commented Sep 26, 2021 at 14:00
  • @Babel they're both in EPSG 3857 - WGS 84 / Pseudo-Mercator
    – Max Muller
    Commented Sep 26, 2021 at 14:27
  • 3
    OK, this is a projected CRS, but lengths (and thus also areas) are heavily distorted towards the poles. Never use this CRS for any lengt/area calculations. Reproject to an equal area CRS like EPSG:6933, see: gis.stackexchange.com/a/412522/88814
    – Babel
    Commented Sep 26, 2021 at 14:30
  • @Babel I've reprojected both the layers and the project to EPS: 6933, but the areas seem to remain the same. Also get a warning message saying "network request to services.arcgisonline.com timed out, any data received is likely incomplete."
    – Max Muller
    Commented Sep 26, 2021 at 14:42
  • OK, so you don't have the data locally? Than you can't reproject, I guess... Can you save your data locally (to a file like Geopackage)?
    – Babel
    Commented Sep 26, 2021 at 14:54


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Browse other questions tagged or ask your own question.