In Chapter 2, Viewing Spatial Data, we talked about CRS and the fact that QGIS offers on-the-fly reprojection to display spatial datasets, which are stored in different CRS, in the same map. Still, in some cases, we will want to permanently reproject a dataset, for example to geoprocess it later on.
In QGIS, reprojecting a vector or raster layer is done by simply saving it with a new CRS. We can save a layer using Layer | Save as ... or Save as … in the layer name context menu. Pick a target file format and file name, and then click on the Browse button besides the CRS field to pick a new CRS.
Besides changing the CRS, the main use case of the Save vector/raster layer dialog is to convert between different file formats. For example, we can load a Shapefile and export it as GeoJSON, Mapinfo MIF, CSV, and so on, or the other way around.
The Save raster layer dialog is also a convenient way to clip/crop rasters by a bounding box, as we can specify...