The Impact of Terrain on the World's Surface Area

Switzerland has overtaken the Netherlands in the official world rankings of surface area. If you factor in the curvature of the earth versus a flat footprint, it would only change the value by like 0.1 to 0.2%. So that's great. Another bit done. And as part of the question Phil said, if they don't include the terrain, do they assume it's perfectly flat? I was like, I don't know how to work that out.