Principles of geographic information systems ITC core module door By, Rolf A., Sc, M.C. Ellis B., Kainz, D.W, Knippers, R.A, Kraak, M.J, Krol, B.G.C.M, Radwan, M.M, Sides, E.J, Sun, Y., Weir, M.J.C, Van Westen, C.J