- The two official world maps (Master Set and Hollow World Set) are not compatible. The Master Set map is seemingly in an equirectangular projection, but does not cover the whole surface of a globe, thus requiring extra ocean to be added. The Hollow World Set map is an artist's impression of a Robinson projection. To sum up, the Hollow World Set map gives the surface lands far more area than the Master Set map.
- The official hex maps are (without exception) all based on the Master Set map. This means that any use of the Hollow World Set map (as for example in fan-made maps) will cause huge inconsistencies.
- The official measurements of Mystara are provided in various supplements, but are not consistent. Moreover, they are very likely not based on the maps; even if they were, necessary alterations to the maps would make recalculation necessary too.
- The Master Set map was created before the advent of the Hollow World, and so does not show polar folding (i.e. where the terrain folds into the gap between the Outer and Hollow World).
- Latitudes are provided differently in various sources. Moreover, they vary quite widely between the Master Set map and the Hollow World Set map.
- Discard the Hollow World Set map for anything other than terrain reference and polar folding reference.
- Recalculate the dimensions of the world using the official hex maps as a reference to determine the scale of the world as depicted in the Master Set map.
- Revise polar folding by adjusting the Master Set map while referencing the Hollow World Set map.
- Determine new latitudes based on the Master Set map.
The position of longitude 0 can be changed - currently I have it set at what looks like -30 degrees, because the map looks a bit weird when it's positioned dead centre. Ultimately this is a non-issue, as it's only a question of how to show the map; it doesn't matter where you cut it.
Here are some snapshots from a Google Earth mock-up. Note that at this point they ignore the existence of the Hollow World.
The Known World. Note the true relative sizes of the various land masses. Norwold and northern Alphatia are likely quite a lot smaller than the hex maps seem to indicate.
Brun. Hyborea is really rather tiny, and most of it is likely in the polar opening. Note the position of the 30 degrees North line, close to Thyatis City, and the 60 degree line in northern Norwold.
Davania is quite huge - but while the northern parts are likely even bigger than fan maps have so far made them appear, the southern parts are actually much smaller.
Skothar. Rather larger than we're used to seeing it, I think - especially the arm and Zyxl, which are very close to the equator.
The Far End Ocean. Astoundingly vast, it literally covers more than half the world. Huge potential here for a community-sourced new world/new continent. If we do decide to add something, I would propose that we make it a shape from another ancient earth map, to keep with Mystaran tradition. (For example the central landmass and islands here: http://www.cpgeosystems.com/430Marect.jpg , or perhaps from one of the earlier maps here: http://www.cpgeosystems.com/rect_globe.html)
It looks like there will be less problems with redoing the polar openings than it looked like from the equirectangular Master Set map. We just have to decide where the lip begins - which should be easy to do once we have worked out the new scale for the globe. We can keep the official dimensions of the polar opening and adapt the surrounding regions as necessary.
As Bruce's polar openings maps in the Hollow World Set show, the southern continent is even easier to flow into the opening.