I have a world map in correct Longitudes from -180° to 180°. Additionally, I have a shapefile of data from South America, which shows at 290° instead of -70°. How can I reproject it using QGIS?
If you load the South American Data into QGIS as WGS84, then
In a second step, you can save the World Mercator file to jet another name and
Note that this method might fail if the North or South pole is included in your data.