On the website The true size of ..., you can shift the shape of countries to other world regions to see the true size (area) on a distorted map (mercator projection). Dragging Greenland over Africa is a classic example (see screenshot below).
Unfortunately, on the site I can't find any information about the procedure in the background - how it's done.
I'm wondering how the same result can be achieved using QGIS only. What I tried and what works as a workaround: Save a screenshot (like the one below), georeference this image (based on the background basemap, using control points in Africa: Juba, Kampala, Nairobi, Harare, Lusaka etc.) and than, on the georeferenced image, vectorize the shape of Greenland.
However, I would like to find a solution using QGIS only, without importing the data. How could this be achieved?
What I tried 2.0 / An idea is to use the following procedure:
Set project CRS to Web-Mercator (
Re-project the same data (country polygons) to a Web-Mercator (
EPSG:3857) and an equal area CRS, e.g.
EPSG:8857to have a layer in each of these CRS. I used the pre-installed basic world countries polygon layer in
worldto the coordinates field at the very bottom of the QGIS main window).
Use the icon
Advanced Digitizing Toolbarand move a feature from the equal area layer (see screenshot). This returns a "true size" version (but heavily distorted in shape) of the original polygon:
Yellow: layer in equal area projection, blue in Mercator - when shifted, the polygon from the equal area layer mainaints the "true size", but the original distortion, inherent in the projection, as well:
To keep the shape, you could do the same with the other layer (in Web-Mercator). The resulting polygon would preserve the shape, but be extremely distorted in size (Greenland almost the same size as Africa). At this point, the new Feature scaling tool (available since QGIS 3.18) could be used. However, how to set an appropriate scale factor? So I guess there must be better options to achieve that.