Zero level

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Building with representation of the zero level

Zero level (sometimes Basement called) is a term used in civil engineering and is the level to which in the dimension of design and construction plans for buildings and other structures in the vertical ( z-axis reference). It is often identical to the upper edge of the finished floor on the ground floor and is specified as the height above sea level or as the height above a reference point such as the middle of the street.

Reference plane in the Cartesian coordinate system

The zero plane for heights in a three-dimensional coordinate system with the axes X, Y and Z is a plane spanned by the axes X and Y, which goes through the zero point (X = 0 / Y = 0 / Z = 0). The Z axis is perpendicular to this plane, which thus forms the reference plane for the Z coordinates. All points on the zero plane have the Z coordinate 0.

Image plane for parallel projections

Any point in space with the designation P (i) and the coordinates X (i), Y (i), Z (i) is projected onto the zero plane at point P '(i) of the zero plane with the coordinates X (i ) and Y (i). A projection onto the plane defined by the X and Y axes is called a plan view or floor plan . In order to be able to represent a three-dimensional object in the same way in the Z-direction, further imaging planes are necessary, which are either in the X and Z planes or in the Y and Z planes. Projections onto a plane aligned with the Z axis are called views or elevations .

Zero plane as height reference

When planning buildings, a local, three-dimensional coordinate system is normally defined parallel or at right angles to the main direction of the building. By default, the zero level for the height of the building is the ground floor level, which is close to the section of the terrain and thus marks the dividing line between above and below ground floors. In the early design phases, a connection to a nationally valid coordinate and height system is not yet necessary; it is only required in later planning phases and is then limited to the necessary information for conversion, for example for the ground floor height (EFH) to the information EFH: ± 0.00 = 214.50 m above sea level NHN as an altitude above sea ​​level . The absolute heights in the entire building can then be converted relative to the zero level using dimensions.

The location of the building in the building site is determined analogously by distances to boundary lines or points and converted by the surveyor for the construction work, who then transfers the building axes and the reference height to the location when setting out the property. Based on these markings, the construction work can again be carried out with the local axis and height system of the construction planning.

For civil engineering structures , a local system aligned with the main axis of the structure is used for planning. The height ± 0 is usually identical to the height of the traffic route or structure in the axis, which can be calculated in the course of the arithmetical axis definition at any point on the axis in the higher-level height system.

Floor designation

In the German-speaking world, the ground floor is sometimes referred to as zero level or level 0 and analogously to this, the upper floors are referred to as level 1, level 2 etc., while the lower floors are referred to as level -1, level -2 etc. This applies in particular to buildings with mixed use and high levels of public traffic, where a clear, unmistakable number of floors facilitates orientation. Level 0 is usually the main access level to the building, from here the internal access branches to other floors or usage levels. Facilities such as reception, delivery, communal facilities and - assuming a suitable internal location - shops are also regularly housed here.

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