Pohjatasoon

Pohjatasoon is a Finnish term used primarily in geometry, architecture, and computer-aided design to denote the base plane, or reference plane, used for measurements and construction of objects. The word combines pohja ("base") and taso ("plane") with the illative suffix -oon, which signals direction toward that plane or focus on that plane.

In mathematics and geometry, pohjatasoon serves as a reference plane from which coordinates, projections, and relationships between elements are defined. In many descriptions, it corresponds to the horizontal reference plane of a Cartesian system and provides a stable foundation for describing heights, distances, and intersections relative to the plane.

In computer-aided design (CAD) and building information modeling (BIM), pohjatasoon is the default working plane used for sketching and initial construction, and often the origin of the coordinate system. Users create features, draw profiles, and position components with reference to pohjatasoon, after which objects may be rotated or projected onto other planes as needed.

Related concepts include other reference planes and working planes used in drafting and 3D modeling, and the idea of a base or foundational plane is common across many technical disciplines.