I would just assume when you, or anyone else, says south they mean 'true' south... same for North. My issue came up because the blueprint shows the direction as magnetic south. Now I have no idea if that's the optimum sunlight gathering direction for my latitude, (all latitudes are different), or if it was based on my house - because, you see, my house sits diagonally.... it's not lined up true north and south... further complicating the issue. Perhaps they drew up the blueprint based on my house? (And remember, this is NOT a roof mount). OR, some other reason?