Moderator edit: Since discussion has died down, the thread has been renamed and moved to the mapping forum for archiving. (Previous title: "How really big Mystara is?")

While I was working about the icosahedron projection issue for Thorf's mapping project I found a severe mismatch about the nominal dimension of Mystara and the hexed map scale.

In short, here is the problem:

From HW (and the PWAs, and Ann Dupuis contribution on the Vaults) we know that Mystara is 6190 miles in diameter (3095 radius). To keep things simple let's say that it is a perfect sphere (no polar openings, no pole flattening, etc.). This means that its circunference is 19446 mi.

So, if you want to go from the Equator to a Pole (from 0° to 90° latitude) you'll have to cross 4861 mi (1/4 of a circunference).

Now, take a look at the map below. It is a merging of PWAII, DotE and CM1 maps in a 72 mi/hex scale. PWAII and DotE maps were already in a 72 mi/hex scale, so the merging was easy. I scaled down CM1 map in order to add the area around Frosthaven.

The orange hex is the nortermost mapped hex available for Mystara. It does not represent the North Pole but, accordingly to HW planetary map it should be north of the Arctic Circle.

The green hex should be placed on the Equator, accordingly to PWAII map. In my opinion this map is wrong, because if you compare the coastlines with the HW planetary map you easily see that the Equator should be farther south than this. Anyway, let's say that the Equator cross the green hex.

There are 81 hexes between the green hex and the orange hex, which means that the total North-South distance shown in the map above is: 81 x 72 = 5832 mi

Which is much more than the 4861 mi "available" for the 0°-90° distance on Mystara.

How can we solve this discrepancy?

In my opinion there are just three possible solutions:

**1)**Mystara is a larger planet than expected; while this seems the easiest solution it arises some problems about the Hollow World and polar opening measurements (see below);

**2)**Hexed scale map is wrong, at every level: a 72 mi/hex map is, in truth, a smaller scale map. In general hexed maps are quite consitent with each other (e.g a 72 mi/hex on a map almost always correspond to three 24 mi/hex on a smaller scale map, and so on), so you'll have to define again the scale of the whole official set of maps;

**3)**Hexed maps are distorted at the higher latitudes: on the same map, an hex near the equator may measure 72 miles in the North-South direction but, at higher latitudes, the same distance across the hex may correspond to 50, 40, 30 miles and so on;

I would like to give an estimate of the re-scaling factor if options 1) or 2) are considered.

In the map below I superimposed the planetary map with a grid (in red) showing the real latidudes of Mystara as if it was a sphere represented with a Robinson projection (click the link below to download the full resolution map):

http://it.geocities.com/lutetius00/Mapp ... binson.jpg

Notice that the planetary map we have is pretty in agreement with such a projection, as it was noticed in this board some time ago: latitudes, tropics and polar circles are almost coincident (incidentally, this shows that Mystara axis tilt is the same as Earth's). The northermost and southernmost areas of the grid shows where the north pole and south pole would be if Mystara was a perfect sphere, without the polar openings (which introduce a pronounced pole flattening).

These areas are approximatively in agreement also with the HW set maps showing the section of Mystara (you can extend the spherical surface over the polar openings to see where the "true" poles would be and then estimate the distance between the 90° circle of the planetary map and the "true" pole).

Notice that the northernomst planetary map latitudes (above 60° or so) do not match with the "real" latitudes of the Robinson projection due to the choice of placing the 90° line at the circle where the polar opening folds inside Mystaran crust. Anyway, given the fact that Robinson latitudes are equally spaced it is easy to estimete the right latitudes.

A rough calculation based on the map above gives a latitude of 79° (approx) for the orange hex on the top of the map, and about 3° for the green hex on the bottom of the map.

Now, back to the options:

Choosing option 1) (enlarge Mystara's radius) you have that 79 - 3 = 76° of latitude would correspond to 5832 mi, which means that Mystara's circunference is some 27625 mi. The new radius would be approximatively 4397 mi. By comparison Earth radius is just 3958 mi, so Mystara should be actually large than Earth.

This option has a problem in defining the Hollow World polar openings. In fact, the inner measurements of the Hollow World sphere are pretty in agreement with the official radius of Mystara planet. For example, the 40 hex/mile map of Iciria, covering most of the NS distance between the polar openings shows 102 hexes in the North-South directions, corresponding to 102 x 40 = 4080 miles.

From HW set we know that the radius of the Hollow World sphere is 1895 mi, corresponding to a circunference of 11906 mi. Half of it would give 5953 mi, which is pretty in agreement with the NS extension of the continent of Iciria calculated above.

This will mean that the HW sphere should be left unchanged even if Mystara radius is enlarged. This implies that Mystara's crust thickness is increased: from the official 1200 miles to the new measurement of 2502 mi.

If you leave the polar opening measurements unchanged (1500 miles radius at the external surface, 500 miles radius in the narrowest point, 1000 miles at the internal surface) you have to stretch the length of the opening, almost doubling the radial distance.

Choosing option 2) (leave Mystara's radius as it is and change the scale map) you have that the 81 NS hexes of the map above cover 76° of latitude, which correspond to 4105 mi, so each hex is 50 miles across (and not 72 miles). You could approximate it to 48 miles/hex (my latitude measurements are, after all, an estimate) and reduce to 2/3 of the original the scale of every official map we have (72 mi/hex to 48 mi/hex, 24 mi/hex to 16 mi/hex, 8 mi/hex to 5.3 mi/hex, and so on).

This scaling would imply the re-calculation of nations' surfaces and density populations.