Export of 2D building geometries (groundfloor, upperfloor, roofs) as geojson? about 3dcitydb HOT 6 CLOSED

Hey, the 3DCityDB Importer/Exporter supports CityJSON too.
https://github.com/3dcitydb/importer-exporter

You can use e.g. an SQL Filter to extract GroundSurfaces:
https://3dcitydb-docs.readthedocs.io/en/latest/impexp/export-filters/sql.html

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For Oracle Spatial you can use SDO_UTIL.GET_2D_FOOTPRINT in combination with SDO_UTIL.TO_GEOJSON.

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Thank you for your feedback :)
@karinpatenge We are looking for an open source solution, so unfortunately I think the Oracle solution we could not use.
@BWibo If I understand CityJSON right, it does not help us. We need to extract the 2D floor geometries.
Can the SQL export filter also filter geometries? I am used to working with geojson - however never much touched CityGML. Is there a way to tell which geometry is a footprint/floor one? Are they usually annotated as 1 continuous polygon for a building - or is it many neighboring geometries per floor?

Thank you for your help,
Best
Andre

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Dear all,

Maybe not really a solution, but a suggestion to solve the problem from another angle...

Have you considered using the 3DCityDB-Tools plugin for QGIS?
It will allow you to interact with data in the 3DCityDB and create "sort of" traditional GIS layers (including lod0 footprints and roofprints). From QGIS, you could then generate GeoJSON using the usual export as...

Beware, layers are generated directly in PostgreSQL, so you could use Python (or whatever you prefer) to convert the layers into GeoJSON from there.

Link: https://github.com/tudelft3d/3DCityDB-Tools-for-QGIS

(Check the user manual) ;-)

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Can the SQL export filter also filter geometries?

If you have LoD2 data, you can filter for BuildingGroundSurfaces using SQL. Check the Building module of 3DCityDB and look for the ThematicSurfaces. UsingPostGIS functions you can for this to 2D.
https://3dcitydb-docs.readthedocs.io/en/latest/3dcitydb/schema/building.html

For LoD1 data this should be possible using PostGIS functions.

I'd recommend to take a look at the building model of CityGML. It won't take very long to get a basic understanding of the model and it will help you a lot!
https://www.ogc.org/standard/citygml/

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@gioagu @BWibo thank you a lot, both of you. I think I can go from there :)

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