Problems with adding CityGML Data

Cesium ion
1

Hi there!

I tried adding CityGML data that is officially available by the state NRW (North Rhine-Westphalia) in Germany. In particular, I was looking forward to add the data of the town Solingen.

At first, there was a problem with the original data. The xml-file starts with:

  <gml:boundedBy>
    <gml:Envelope srsName="urn:adv:crs:ETRS89_UTM32*DE_DHHN2016_NH*GCG2016">
      <gml:lowerCorner srsDimension="3">356000.0 5668000.0 45.529</gml:lowerCorner>
      <gml:upperCorner srsDimension="3">357000.0 5669000.0 77.537</gml:upperCorner>
    </gml:Envelope>
  </gml:boundedBy>

However, Cesium Ion was not able to load this data - there seems to be a problem with the interpretation of the srsName.
With the help of this forum and some information on your website I was able to find out that this information should be equal to (see ETRS89 / UTM zone 32N - EPSG:25832). Therefore, I changed the srsName:

<gml:Envelope srsName="EPSG:25833">

Now Cesium Ion was able to upload the data and start the tiling process, but the buildings are placed at the wrong coordinates. I guess, there must be more information in the original srsName than I thought…

Can anybody help me to add this data?

@Shehzan_Mohammed Wouldn’t it be possible to add such data (free and officially available) to the standard Asset Depot?

2

Hi @DavMic17

I’ve been through exactly what you have described. We have tiled plenty of other CityGML datasets, but the NRW dataset always proved elusive.

The problem with the srsName is that its expected to be computer understandable, but software like GDAL does not recognize it, requiring users like you and us to have to find-replace it with the EPSG code.

The Asset Depot is meant to a curated set of assets around the world. These have to pass a reasonably high bar of quality and broad usability before we decide to make them available to all users. If we were to region based 3D cities, that would mean way too many datasets for us to maintain and too many for users to add. Thats why we have chosen to go the Cesium OSM Buildings route and create one global 3D buildings assets.

This does not rule out that in the future we will have an asset that is the best of both worlds. Where there is high-quality data from CityGML or other open sources, we could use that, and fall back to OSM as needed. We don’t have a timeline for this, but its a possibility that we will explore when the time is right.

Shehzan

3

Hi @Shehzan_Mohammed!

Thanks for your reply. I can see why it doesn’t make sense to add this data to your global dataset…

However, it would be great if you could help me find out, why the positions of the buildings are wrong. I am pretty sure that I have found the right EPSG code for this cityGML data set…

Thanks a lot in advance!