SOS Format Requirements
Because of SOS’s high resolution requirements, it is generally easier to have a base map of vector data, which can be scaled indefinitely. Raster, or image, data works if it is high enough resolution, but images of sufficiently high resolution are uncommon.
Additionally, SOS’s software needs to be given a specific map projection in order to render the map correctly on the sphere. In QGIS, this is the default projection: the Equatorial Cylindrical Equidistant projection, also known as WGS 84 or EPSG:4326. While this is a relatively common map projection, it is NOT the one used by anything that Google Maps has made, or anything with Google Maps as a background. There are a lot of tutorials for QGIS that assume a Google Map will be a fine base map, so they tell users how to import that and skip over the instructions for importing anything else.
Because of this limitation, the underlying map layer is a little more complicated when making an SOS map than it is when making a normal map.
Natural Earth DataPermalink to Natural Earth Data
It is certainly possible to import a vector map in the correct projection. They’re just not very easy to find. A good place to go is Natural Earth Data. Click on the green Get the Data button near the top of the page. From that page, you can download the “Natural Earth quick start kit” or browse the available resources. If you choose to download the quick start kit, you will get a zip file that contains a folder called “packages”. Inside is a .qgs file called “Natural_Earth_quick_start_for_QGIS.” To get started, it’s a fun one to play with.
Other Supported FormatsPermalink to Other Supported Formats
If you want to find a vector map from another source, QGIS accepts the following forms of vector data:
Start by trying to find data in one of these formats. Websites from NASA, NOAA, and other government agencies will occasionally have mapping data available to the public.
Using an ImagePermalink to Using an Image
It is also possible to put an image as the base of your map, provided the image is of high enough resolution (2048×1024 or 4096×2048 pixels for SOS). SOS’s FTP server is a good place to find high resolution images that are already in the right format.