Reprojecting over the Pacific Ocean with EPSG:3832 gives artefacts

Question

I am trying to center the Natuarl Earth 10m on the Pacific. I have followed instructions from QGIS Tutorial: How to Change the Map Projection to be Centered Over the Pacific Ocean.

When I change projection to EPSG:3832 the map in QGIS becomes fragmented:

How can I fix this? Do I need to define my own CRS entry?

I have seen other replies here Displaying world country shapefiles centered on Pacific Ocean using Robinson or Miller Cylindrical projection in QGIS? but that is 7 years old.

This is an edit: Interestingly open street map seems to reproject to 3832 ok. Slow and blurry though.

Answer 1

Artifacts are caused by the polygons that crosses the antimeridian, which for your projection is defined at -30 degrees.

Therefore you must find a way to create a polygon centered at -30 degrees, with a thin thickness.

Just to show another way to do it:

• Create a new temporary scratch layer, of Linestring type, defined in geographic coordinates, and digitize a simple line with the approximate location of the -30 degrees meridian. Enable vertex editing and enter the exact coordinates of each of them:

• Save the changes to the temporary layer and perform a buffer of a small (in degrees) size to the line layer. You can use any small numer for the radius, like 0.00001.

• Lastly, perform the difference between the Natural Earth Layer and the Buffered layer. Now you can reproject the map to EPSG:3832:

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Notes:

• The geometries coordinates are being preserved as geographic coordinates, reprojected only on the fly to the map canvas.
• Remember that a Mercator projectio projects to infinite the poles.
• The way to disable on the fly reprojection, in QGIS 3, is selecting "No projection" in the CRS tab of the project properties. It is not necessary for this Mercator projection.