A distinction is made between primary geometry, the arrangement in space of lines of projection from a 3-D object to a plane of projection, and secondary geometry, the relationships between the points, lines and shapes of the drawn projection on a 2-D surface. Drawing projection systems, such as those classified under British Standard 1192, are illustrated, and are shown to be defined in terms of primary geometry. It is argued that a re-classification of projection systems in terms of secondary geometry enables first-year students of drawing to relate more easily such systems of geometry to their observational experiences. Student drawings illustrate the argument.