Cannot set Coordinate Reference System for uploaded LAZ file

Cesium ion
1

I can upload a LAZ file to create a “3D Tiles” object that is accessed as Cesium.Cesium3DTileset.fromIonAssetId(2882504)

I know this pointcloud should be assigned Coordinate Reference System (CRS)
EPSG:21781 because I can do this in QGIS and it aligns with the base world map.

Unfortunately the only option in the 3D Tiles Location Editor is to give it a Lat and Long coordinates. Nowhere is it possible to assign its proper CRS attribute.

It looks like there should be a feature to do this, but it doesn’t seem to be accessible through this web user interface Add a property to specify the CRS of the tileset · Issue #504 · CesiumGS/3d-tiles · GitHub

2

Hi,

This is good feedback for our UI. We currently do allow users to specify an input CRS on API uploads but not on the UI. Can you please describe your use case for specifying a CRS and I will create an issue for our team to take a look at.

Thanks,
Ankit

3

Hi Ankit,

The use cases are these Lidar cave and mine scans that are useful when they are registered with the CRS (as they come out of the Leica survey software), where it would be great to load them into context of the surrounding landscape in Cesium.

I’ve got a bit more information about the application(s), which I will try to explain to you.

I have been rendering pointscans of caves in potree for a couple of years. I ported the potree protocol into Godot in an an app called tunnelvr that is used to trace up and annotate the pointscans in 3D VR https://github.com/tunnelvr/tunnelvr

I was looking again at Cesium after the announcement of a cesium plugin for godot. (I’d like to subscribe to any news on that or get early access if possible). If it is performant enough and the processing works, I’d like to swap out potree for cesium.

Recently I made contact with a project in Switzerland who are scanning caves and attempting and making models: https://erc-karst.eu/

They showed me the pointscans of caves/mines in their locality, such as this one, which is also hosted in potree:

https://sitn.ne.ch/lidar/mines/petiteminedetravers/

Then they showed me this local pointscan system made by the municipality they are in where it overlays the different years and datasets.

This is also done using potree.

https://sitn.ne.ch/lidar/

I draw your attention to the layer called: “Virtual City bati 3D > LiDAR”

Turn off the other layers and zoom to a building close to the lakeside and you will see that the points are in a grid. This means they have a 3D surface model of their buildings which they resampled down into a pointcloud to make it compatible with potree, which only uses pointclouds.

I believe they did it this way because they didn’t know about Cesium, because it would make more sense to serve triangular models as triangular models when you have them.

Anyway, hope some of this makes sense and is helpful to you. If you’ve got any news on the Godot Cesium plugin, I’d like to know more about it.

Yours,

Julian Todd.

4

Hi,

Thank you for your detailed write-up of your use case, this will be extremely helpful. The current update for Cesium for Godot plugin is being developed as part of a Cesium Ecosystem Grant by Battleroad and is scheduled to go out sometime late January or early February of next year.

Thanks,
Ankit