The complete structure of the packet can be found in

.
If you need to calculate between "packet coordinates" and "game coordinates", use

.
Game coordinates, also known as world coordinates, are only a visual simplification for the user (at minimap).
Packet coordinates, also known as region or local coordinates, have a regionID (which can be split into X and Y) and X-,Y-, ZOffsets (~0 to ~1920, except Y which is unbounded).