Refers to all forms of parallel projection, particularly where at least one of the three spatial axes is inclined to the plane of projection or picture surface. It is often used to refer to projections depicted as if a plan were drawn to scale, and the plan is then tilted at a 45 degree angle to provide a third dimension, typically height, which is drawn to the same scale as the plan. This system for projection depicts both the plan and volume simultaneously and with a consistent measurement, without the distortion caused by the converging lines of one-point perspective.
