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Last edited 13 May 2022

Orthogonal plan

The term 'orthogonal' refers to objects that, in Euclidean geometry, are related by perpendicularity. The etymology of the term is the Greek ‘ortho’ meaning ‘right’, and ‘gon’ meaning ‘angled’.

Orthogonal projection is a drawing technique used to represent three-dimensional objects as a series of two-dimensional 'flat' drawings in which there is no perspective.

Orthographic projection is a type of 'parallel' projection in which the four orthogonal views of an object are shown. The orthographic projection commonly used in the UK is called first angle projection.

Buildings are commonly depicted orthogonally by a series of elevations and plans.

The orthographic projection commonly used in the UK is called first angle projection.

The term 'orthogonal plan' may also refer to a type of urban design layout that consists of mostly square street blocks with straight streets intersecting at right angles. This forms a grid pattern, commonly referred to as a ‘grid plan’ or ‘gridiron’.

Orthogonal plans for urban design date back to antiquity, and contributed to the building of some the earliest planned cities. The layout is commonly credited to the 5th-century Greek philosopher Hippodamus, who championed this method of urban planning in his Hippodamian Plan. However, archaeologists have cast doubt on his true claim having found evidence of such plans (more accurately referred to as Milesian layouts) in ancient Egypt.

The regular orthogonal plans of the ancient Greek and Hellenic societies influenced the ancient Romans, who established design principles that are often followed to this day; particularly the work of the engineer Vitruvius.

In a modern context, grid plan urbanism has come to be closely associated with America and recently-redesigned cities such as Barcelona (outside of its historic core).

Although orthogonal plans can help with orientation and enable directness of route due to frequent intersections, the infrastructure cost associated with regular grid patterns is often higher than for patterns with discontinuous streets.