I downloaded the global SRTM DEM from here. When I add the DEM as a raster layer (in my case topo30.grs file) the left/western edge of the file is at Greenwich and the right/eastern edge is at +360 degrees. This makes the layer run off the right side of the required area. The western hemisphere needs to be negative up to -180 degrees. I have attached an image which shows what I mean. Is there an easy way to import it with the right projection or reproject the SRTM. I don't understand why they created the DEM like this in the first place.