Upgrading your code for v1.1

The following 11 changes need to be considered:

  1. 1. "version" (obviously)
  2. 2. "transform" property is mandatory
  3. 3. the "lod" for each Geometry is now a X.Y string (and not a number)
  4. 4. "metadata/referenceSystem" is now using OGC URLs
  5. 5. Metadata properties are now limited to those 6
  6. 6. "CityObjectGroup": "members" -> "children"
  7. 7. "GenericCityObject" does not exist anymore
  8. 8. New City Objects from CityGML v3.0 have been added
  9. 9. "BridgeConstructionElement" -> "BridgeConstructiveElement"
  10. 10. "geometry" is not mandatory anymore
  11. 11. If relevant, support the type "CityJSONFeature"

1. "version" (obviously) 

"version": "1.1"

2. "transform" property is mandatory

Files are thus always compressed.

3. the "lod" for each Geometry is now a X.Y string (and not a number) 

"lod": "2.2"

4. "metadata/referenceSystem" is now using OGC URLs 

"metadata": {
  "referenceSystem": "https://www.opengis.net/def/crs/EPSG/0/2355"
}

The coordinate reference system (CRS) may be given as a URL, formatted this way according to the OGC Name Type Specification:

http://www.opengis.net/def/crs/{authority}/{version}/{code}

where {authority} designates the authority responsible for the definition of this CRS (usually “EPSG” or “OGC”), and where {version} designates the specific version of the CRS (“0” (zero) is used if there is no version).

5. Metadata properties are now limited to those 6 

"metadata": {
  "identifier": "eaeceeaa-3f66-429a-b81d-bbc6140b8c1c",
  "pointOfContact": {
    "contactName": "3D geoinformation group, Delft University of Technology",
    "contactType": "organization",
    "role": "owner",
    "phone": "+31-6666666666",
    "emailAddress": "3dgeoinfo-bk@tudelft.nl",
    "website": "https://3d.bk.tudelft.nl",
    "address": "Julianalaan 134, Delft 2628BL, the Netherlands"
  },
  "referenceDate": "1977-02-28",
  "title": "Buildings in LoD2.3 of Chibougamau, Québec",
  "geographicExtent": [ 84710.1, 446846.0, -5.3, 84757.1, 446944.0, 40.9 ],
  "referenceSystem": "https://www.opengis.net/def/crs/EPSG/0/2355"
}

The storage of additional ISO19115-compliant metadata attributes and/or of statistics related to 3D city models can be done with the MetadataExtended Extension.

6. "CityObjectGroup": "members" -> "children"

and the children need to add the group ID as a "parents"

This harmonises the "CityObjectGroup" with the other City Objects in CityJSON.

7. "GenericCityObject" does not exist anymore

Instead, an Extension needs to be used.

You can just use the type "+GenericCityObject" we have defined with its Extension schema hosted there.

"extensions":
{
  "Generic":
  {
    "url": "https://www.cityjson.org/extensions/download/generic.ext.json",
    "version": "1.0"
  }
}

The resulting file would look like this.

8. New City Objects from CityGML v3.0 have been added

  • "BridgeRoom"
  • "BridgeFurniture"
  • "BuildingConstructiveElement"
  • "BuildingFurniture"
  • "BuildingStorey"
  • "BuildingRoom"
  • "BuildingUnit"
  • OtherConstruction
  • "TunnelConstructiveElement"
  • "TunnelHollowSpace"
  • "TunnelFurniture"
  • "Waterway"

These behave exactly as the other City Objects (and thus no code should have to be modified).

9. "BridgeConstructionElement" -> "BridgeConstructiveElement"

For reasons that are not understood by nobody, CityGML v3 decided to rename "BridgeConstructionElement" to "BridgeConstructiveElement".

So CityJSON did the same too.

10. "geometry" is not mandatory anymore

City Objects do not have to have a "geometry" property anymore (in v1.0 an empty array was required).

11. If relevant, support the type "CityJSONFeature"

This is relevant in the context of streaming datasets on the web, eg for the OGC API - Features.

See the specifications for more details.