Last edited 05 Feb 2018

Orthogonal plan

Orthographic projection.jpg

Orthogonal is a term used to refer to objects that, in Euclidean geometry, are related by their perpendicularity to one another. The etymology of the term is the Greek ‘ortho’ meaning ‘right’, and ‘gon’ meaning ‘angled’.

An orthogonal projection is a drawing technique used for viewing three-dimensional objects with a linear perspective. Lines of perspective are drawn along parallel lines until they meet at the ‘vanishing point’, making them orthogonally related to one another. Two vectors are considered to be orthogonally related if they form a 90-degree angle.


An orthogonal plan is 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, leading to it becoming 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, although archaeologists have cast doubt on his true claim having found evidence of such layouts from 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.

Although orthogonal plans can help with orientation and enabling the directness of route due to its frequent intersections, the infrastructure cost associated with regular grid patterns is often higher than for patterns with discontinuous streets. The varying factors that determine the street costs include:

  • Width of the street.
  • Length of the street.
  • Width of the block.
  • Width of the pavement.

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