Gabby Getz

@jjspace Can you please review?

Hi @Alforoan! Is the plan to still move forward with this PR? Do you need any additional help to get this over the finish line?

@Alforoan Is this ready for another look?

I'm closing this issue due to inactivity. If you believe this is still an issue, please feel free to re-open. Thanks!

Here's another [Sandcastle which breaks with the same stack](https://sandcastle.cesium.com/#c=vVLLbtswEPyVhU40oFCymzRIKhttnWOLFKnQXnRhqHW0KB8CSdlwi/x7Kcpu0sS99iJohzOzu0NKa3yALeEOHSzB4A7W6GnQ/FvCWJPJVK+tCYIMuibL4VdjAAI6F5Hro6Cear5xVn+3TrUHgM3yxjzO3jWmMTK1s15/HEi1ZB58TQo9hthb7ASFo5l0KALePiN+8Hsj2WgzTcu9RIO8d6Qp0BY9F23LTlhPnf8SSaHRCb5R+9qytEyLPpARgezTQmvhQvwT5k3a6QYfHKJnZ5fnvJxf5XBe8rdX80UOlxfluCOAdYQxpskl+QJ0KMZp/rh+FqHjwd5FVBjPFgcpQE9Bdv+inR15j+nbDu7QpZzChad0W1RiH/PUHpardKNf4vTkkTlMUMykJo12CCOSR+JszGjKP6nZRVmWJ3LT1vVdbRc3bDo8JfkvQb/eP8uzyoe9wtWUJsB70r11AQanGOdFQN2r+KZ8cT/IHxi49H6cd6RWxXNp1dIWqF2eePoglfA+nmwGpb7ST2yyVVVE/iupsunab7foYjojrZuvPk0g57wqYnlaGaxV98K9cP4N)

Another possibility could be to [throw a differentiated error](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error) in the case where a Cartographic does not exist. Though, regardless, we'll need to be careful about introducing any breaking changes...

@jjspace I see quite a few failing specs when running locally: Failing test logs ``` 1) renders tileset with custom up and forward axes Scene/Cesium3DTileset Expected 107 to be less...

Thanks @jjspace! I pushed a small change to the specs to allow for a 1-byte tolerance in the render tests. This allowed all the specs to pass on my machine.

Looks awesome! 😎

@javagl Would you call these duplicates? I'd be in favor of consolidating these issues.