Omitted elevation aligns object to ground/road level

For WorldPosition and RelativeWorldPosition z=0 is unambiguous. However, for many use cases the desired elevation of an object is on ground (or road) and it can be tricky to know the elevation of a given x, y position. Hence I think it would make sense to interpret omitted z value as the wish to place the object on the ground/road. And still, if z=0 is desired regardless of ground level, it's easily specified.

It's true that this kind of brakes backward compatibility. Not in terms of XSD changes, but in terms of interpretation. However, I think the gained user friendliness is a good reason. The workaround for any broken existing scenarios (which implicitly put objects at z=0 AND this happens to be not aligned with ground/road level AND this is desired) is simply to add "z=0" explicitly in the Position.

Let's discuss this suggestions in project group to find out priority and if it's worth to refine proposal.