Reality capture to Cesium - Z Axis issue

Cesium ion
1

Hi all,

I have encounter 2 issues when I upload the models to Cesiums.

Issue1:
I have created a photogrammetry model from Reality Capture with Geo-reference Data, I am trying to upload it on the Cesium. I manage to upload to model that will sit on the WGS84 Ellipsoid, but I want to try to create a model that will be sitting on Google Photorealistic 3D tiles.

The main challenge I am encountering with the different terrains is that the elevation of each seems to differ by up to 20metres +/- which I assume indicates they are using different geoid heights/ coordinate systems. We have been exporting an UAV models from Reality capture following the WGS84 system which works well with the WGS84 ellipsoid terrain as one would expect but due to the elevation difference of the terrains as mentioned above, we cant get it to automatically clamp to the surface of the other terrain systems.

Is there any method that’s allows the model to export and co-ordinate our data in line with the base model provided by Cesium? Specifically the Google Photorealistic 3D tiles.

Issue 2:
I have two photogrammetry models captured from locations on the same street but a short distance apart. Both models contain RTK data, and one of them includes a curved hill. When I directly upload these models to Cesium, there’s a noticeable difference in the Z-axis alignment. The model with the curved hill appears to be significantly higher than the one that is flat on the Z-axis. Are there any solutions to align these two models together?

Thank you

2

Hi,

For Google’s Photorealisitic 3D Tiles’ elevation differences, Google is aware of issues like these. Since this is still an experimental feature, they will be preparing documentation in the near future to provide users with more information about the elevation in their data. Unfortunately, we cannot provide you with a timeline for when the documentation will be released. Please also let google know about the requirement of more detailed information about their elevation through this page.

As a temporary workaround, you can manually update the positions of the assets you are exporting from Reality Capture. You should be able to set any capture asset’s position relative to Google’s Photorealistic 3D Tiles through Cesium stories. You can create a new story and set your base terrain to Photorealistic tiles like so:

image

Then add your asset to the story and click the 3 dots on to adjust its position:

image

You should now be able to visually position the asset relative to Google’s Photorealistic 3D Tiles. Once you save the position it will be carried over everywhere.

Similarly for your second issue, you can load these models into Cesium Stories and align then manually and visually on top of any terrain with the help of the Adjust tileset location option stated above.

Thanks,
Ankit