I'm dealing with image transforms.These are of course 2D. I always thought orthogonality was the same as perpendicularity, so the max number of orthogonal bases you could come up with in 2D is 2. However, image processing is full of transforms such as Hadamard, Haar, etc. that can have often 8 different bases. Trouble is, they are described as orthogonal. How can you have 8 bases that are orthogonal to each other if we are in 2D all the time?