A contour line, in the context of commercial construction projects in Australia, refers to an imaginary line on a map or drawing that represents a continuous point of elevation on the Earth's surface. Contour lines are used to depict the shape and features of the land, including its elevation, slope, and drainage patterns.

In Australia, the use of contour lines in construction projects is subject to various standards and regulations, including:

•  AS 2124: This standard covers the general requirements for the preparation of plans and specifications for building and construction projects, including the use of contour lines to represent site topography .
•  AS 4000: This standard form contract is widely used in the construction industry and requires contractors to provide details of the project, including site plans and drawings that may include contour lines .
•  AS/NZS 1170: This standard provides requirements for the structural design of buildings, including the consideration of site topography and drainage, which can be represented using contour lines .
•  Building Code of Australia (BCA): The BCA requires buildings to be designed and constructed to withstand various loads and forces, including those related to site topography and drainage, which can be assessed using contour lines .

In commercial construction projects, contour lines are used to:

•  Determine site drainage patterns and potential water accumulation areas
•  Identify potential landslide or erosion risks
•  Inform the design of building foundations, footings, and other structural elements
•  Plan site grading and excavation works
•  Ensure compliance with relevant building codes and standards