3D Buildings 2013 (LOD 1 — Level of Detail 1)

The buildings are derived from the topographic database (BD-TOPO-L) of the Cadastre and Topography Administration, based on aerial images from 2013.

The data of type LOD 1 (Level of detail 1) represent simple blocks without details at the roof level.

### Building height

The height of the blocks is defined by the mean height of the vertex of the outer perimeter of the roofs from the photogrammetric measurements (i.e. the extraction of horizontal information (X,Y) and vertical (Z) based on aerial images). The survey of these outer roof perimeters is part of the 2013 topographic survey for updating the topography database (BD-TOPO-L).

### Resolution of buildings

The origin of this data restricts the resolution of units at the level of building blocks, thinner units such as adjoining buildings or remarkable partial sections (e.g. church tower) are indistinguishable.

### Data structure and format

The data is available in the form of [CityGML](https://www.opengeospatial.org/standards/citygml), a standard format for the exchange of 3D data. The buildings can be downloaded as ZIP files per municipality (± 10 mo/mb per file), by canton (± 40 mo/mb per file) or for the whole country (± 600 mo/mb).

The data are projected in LUREF (EPSG:2169), i.e. a coordinate reference system using values in meter [m].