by Aaron » Sun Jan 19, 2014 12:07 pm
Hi Demi,
Thanks for the question.
As you've noticed, the size of features in maps is not set in absolute terms, but but rather is relative to the size of the map. This means that the 'feature scale' control in the design map window is asking for input like "make a typical mountain cover 20% of the map", rather than "make a typical mountain 20km wide." Consequently, when you shrink or enlarge the map, you also shrink or enlarge the features proportionately (assuming you don't change feature scale at the same time.) The vertical scaling gets caught up in this by virtue of the need to maintain a relatively constant slope with changing map sizes, so that when you make the map smaller, for instance, the size of the hills in both the horizontal and vertical axes scale down together to maintain the same overall shape & slope.
Thus, if you want to enlarge the map but keep the same absolute feature size, you need to decrease the 'feature scale' setting by the same factor by which you increased the map size.
This algorithm was originally designed this way with the thought that novice users would find it much easier to get acceptable results using simple relative feature-size controls. The counter-position, which would presumably involve absolute feature size controls for horizontal and vertical scaling, would perhaps be more predictable for experienced users, but would be a minefield for new users, who would find it all too easy to make very flat or very steep maps if they didn't think very carefully about the geometry of the scaling settings they choose.
As for when this change came about; I think it was L3DT release 2.0 in 2003. I don't think I've touched this algorithm since, other than perhaps to tweak some of the relative scaling parameters now and then (though probably not since 2005).
Best regards,
Aaron.