A point in a 3D Cartesian system is written as an ordered triple (x,y,z). The order matters. The third coordinate records position along a third axis, commonly height/depth.
Coordinates are meaningful only after the origin, axis directions and units are defined. The same physical location can have different coordinates if the reference system changes.
A plan view may hide height, while an elevation may hide depth. Layers can represent floors in a car park or levels in a game. Dynamic software lets students rotate a model and compare views without changing the underlying coordinates.
Preserve the full AC9 contexts: aircraft/drones using latitude–longitude–altitude, 3D printing/design software, virtual maps versus street views, first-octant constructions, multi-storey car parks, 3D noughts-and-crosses, and respectful exploration of geospatial technologies used by First Nations communities.