The direct use of satellites is already beginning to have enormous influence on the development of civilisation in our world. An initial study of the benefits to be obtained for mankind by the use of satellites to survey the natural and man-made resources of the earth leads to the inescapable conclusion that this will undoubtedly be one of the major applications of satellite technology that will evolve in the next few years. It is only very few years ago that the real impact of this use of space became evident, but already in that period of time an extremely wide range of types of measurements and different use of such data has been examined and a considerable amount of experimental work been carried out both in earth terrestrial laboratory conditions and also using equipment orbiting in space. There is now a wealth of data on what is possible already and might be possible in this new field of endeavour. I shall attempt in this paper to summarise the main potentialities of different types of systems and try and relate some of the key elements of the satellites to the natural resources being observed.