# Building geometry API ## **Dataset** The building geometry dataset ([**3D BAG**](https://docs.3dbag.nl/en/)) is an up-to-date dataset containing 3D building models of the Netherlands. It contains 3D models at multiple levels of detail ([**LOD**](https://docs.3dbag.nl/en/schema/layers/)), which are generated by combining two open data sets: the building data from the [**BAG**](https://docs.3dbag.nl/en/overview/sources/#BAG) and the height data from the [**AHN**](https://docs.3dbag.nl/en/overview/sources/#AHN). There are data attributes describing a building: the number of floors and the area but also information about the surfaces of a building: surface type, area, perimeter, geometry. The goal of the Building geometry API is to expose this information to be able to fetch the geometry data of a single object. ## Use case * Use building geometry data in the addition to the Sustainability API for improved calculations * Retrieve roof surface area's, its orientation and sloping * Extract the orientation of the walls and its (shared) wallsurfaces * Extract the object polygons in GeoJSON format --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.altum.ai/english/sustainability/building-geometry-api.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.