Scene Viewer in ArcGIS Enterprise includes World Elevation Services from ArcGIS Online. In some areas, these services have a 30-meter resolution. If you have higher-resolution elevation data for a particular area, you can publish it as a cached image service, add it to your portal, and use it in Scene Viewer to provide a higher-resolution elevation surface on which to draw your 3D hosted scene layers.
Prepare source data
Obtain source elevation data for your area of interest. The source data can be from lidar, photogrammetry, spot, or contour sources, but you need to create a DTM from it. Save the derived raster DTM as a stand-alone TIFF or load it into a geodatabase as a raster dataset.
Publish the service
Once the DTM dataset has been configured, publish it as a cached image service from ArcGIS Pro.
You can share elevation layers from ArcGIS Pro to your active portal as web elevation layers 
. Web elevation layers can supplement the default Terrain3D elevation layer used in Scene Viewer with higher-resolution elevation data for your area of interest. Like other web layers, web elevation layers can also be added from your portal to ArcGIS Pro.
For more information on publishing web elevation layers from ArcGIS Pro, see Share a web elevation layer and Configure a web elevation layer.
For more information on publishing web imagery layers from ArcGIS Pro, see Share a web imagery layer and Configure a web imagery layer.
Once you have completed the workflow, you can add the layer to Scene Viewer. See Add layers in the Create scenes section of the portal user help for more information.