“…The simplest solution is to show at least two views: usually a map with cross-sections, analogous to the plan and elevation drawings of architects and engineers (Ferguson 1992). Several authors (Johnson and Richter 1979;German and Johnson 1983, 193-198;Reasenberg and Ellsworth 1982;Wells 2002) have used pairs of stereoscopic drawings; when each is viewed with one eye, the fused drawing gives a convincing sense of depth thanks to the human system of binocular vision. For individuals, this requires either severe myopia or special viewers.…”