Add note how to interpret coordinates in absence of referenceSystem

[vmirgorod]

Hello, I have CityJSON file with the following structure:

"type": "CityJSON",
  "version": "2.0",
  "metadata": {
    "geographicalExtent": [
      983.16,
      340433.878,
      27.861,
      1510.432,
      341048.5,
      84.987
    ]
  },
  ...

So, no referenceSystem is given and there is unclear, how to use geographicalExtent and other coordinates.
Can you please add example for the above case what EPSG should be used?

[hugoledoux]

If no EPSG is given then you should ask the provider of the data for it, I wouldn't know how otherwise.

To obtain the real-world coordinates, you need to use the "transform" property, as explained in this page: https://www.cityjson.org/dev/realcoords/