Here's a 3D version used in the creation of sparse voxel octrees:

https://forceflow.be/2013/10/07/morton-encodingdecoding-thro...

Here's an example from AWS, where lat/long pairs are put into a Z-index, which is used as a DynamoDB sort key, letting you efficiently query for items near a point.

https://aws.amazon.com/blogs/database/z-order-indexing-for-m...