The SPI published boardgame map consisted of three 28x22" map; Map C has a 90 degree rotation relative to the other two. Additionally, Map A and B overlapped by 17 hexes making these hexes redundant on this overlap area on map C.. Each mapboard has its own hex ID system starting at 0101 and incrementing across to or 3901 or 6001 (depending on map orientation) and down to 0127 or 0160 (depending on map orientation). A hex id in the boardgame is designated as A2121, B1729, C1212, etc.
The WBS 'Full Campaign' map is a single image with a single continuous hex id system. The overlap and map joining is accounted for. By default, this hex id system differs from the boardgame map. If both players are using the vassal map, this is not an issue. However if reference is made between the vassal map and the boardgame map, two translations are needed.