DEM ImageServer is not smooth in the ArcGIS Online SceneViewer

[MaximeDemers]

Hi,

I have a hosted DEM ImageServer on ArcGIS Enterprise 10.6.1. When I use the DEM as the ground elevation in the ArcGIS Online Scene Viewer, the ground is not smooth as you can see in the image below.

DEM with tiled basemap over it in ArcGIS Online Scene Viewer

However, the same DEM with the same basemap in the ArcGIS Enterprise 10.6.1 Scene Viewer display smoothed correctly

DEM with tiled basemap over it in ArcGIS Enterprise 10.6.1 Scene Viewer

I think something have changed in ArcGIS Online Scene Viewer, because just few weeks ago the same DEM was displayed correctly.

Is there a way to solve the problem and ensure that the hosted DEM will be displayed correctly in both Enterprise and ArcGIS Online Scene Viewer?

[AndreasUlmer]

ArcGIS Online enabled terrain shading in a recent release:
https://developers.arcgis.com/javascript/latest/4.26/#improved-terrain
10.6.1 did not have terrain shading yet.

Our assumption is that the terrain data is actually the same, i.e. already not smooth 10.6.1, but the steps are not visible without terrain shading.
To doublecheck this assumption we'd need some more info:
* is this a custom DEM? Or the default world elevation service provided by Esri?
* if custom, is it possible to share a url to the layer / the service?
* if not custom: please share the exact location where the problem occurs so we can investigate further. You can do this in SceneViewer Share Dialog, Share link, which will include viewpoint in the url.

[MaximeDemers]

Hello @AndreasUlmer,  thank you very much for your reply!

Yes this is a custom DEM based on our lidar data. You can find the ImageServer here: https://cartes.ville.sherbrooke.qc.ca/arcgis/rest/services/DEM_3857/ImageServer 

Tiles are generated for levels 0 to 20 inclusively.

Maybe the 1m pixel size is the problem?

I'm very interested in understanding the cause of the problem. Please keep me informed following your investigation.

[AndreasUlmer]

Thanks for the service link. Unfortunately it is not working for me.

https://cartes.ville.sherbrooke.qc.ca/arcgis/rest/services/DEM_3857/ImageServer
Browser reports "connection has timed out" / "took too long to respond".

* Can you doublecheck the url, and check if it still works for you?
* Confirm that it is indeed publicly available, not limited to your intranet, and no credentials are needed to access it?

[MaximeDemers]

So sorry for that. I confirm the link is correct and publicly available but, for "security" reason, the arcgis server is not available outside Canada and USA. I suppose you are located somewhere else?

Unfortunately, I have no means to share the service elsewhere you could have access outside Canada and USA. This is something out of my control as it is managed by our IT infrastructure team.

If maybe you have acces to a VPN service like NordVPN, than it should work.

[AndreasUlmer]

Thanks Maxime

We were able to read the service and reproduce the reported behavior.
We'll do some more investigations and get back to you.

[AndreasUlmer]

Assumption confirmed:
Data is the same in older versions (e.g. 10.6.1): The same "steps" can be seen on the grid when basemap is disabled.

In older versions those steps were not or barely noticeable due to the flat shading where surface normals were ignored. With the new terrain shading (think dynamic relief) these terrain details become visible.

So the problem lies in the data / the DEM, or the way it was created.
I'm not an expert on DEMs, I would say though that the data resolution is lower than the resolution of the DEM, and that could create these step-like artefacts. I'm also not clear if there are additional interpolation options which allow to control this behavior. I would try to create the DEM with a lower resolution, which matches the resolution of the source data.

For more detailed help I recommend to ask again in the ArcGIS Pro section, or whichever product is used to create the DEM.