Fun with Trigonometry
In recent decades, most official maps of the Forgotten Realms campaign setting include graphics indicating the scale involved. Often, the graphic on a given map is a ruler-like bar representing a certain distance in miles. Older maps sometimes omit this graphic, instead declaring “1 inch = such-and-such miles,” a statement which serves the same purpose.
All of which is great, except it neglects to take the curvature of the planet Toril into account. Any graphic or text equating X distance on the east-west axis of the map to Y distance in miles can only be accurate at one or two specific latitudes. Move a few degrees north or south on the map, and X distance on the east-west axis no longer equals Y distance in miles.
The one-hundred-and-twenty-something interior maps in the Forgotten Realms Travel Guide take the curvature of Toril into account in several ways. First, each map displays arcs of latitude and longitude, labeled in degrees. If you’re a stickler for precise measurements, a chart included in the book summarizes how you can convert degrees at various latitudes into Faerûnian miles.
Since referencing a chart can be inconvenient, most maps also include a graphical indication of scale. This indicator resembles the ruler-like bar used on most official maps of the Forgotten Realms, except the ruler curves to follow one specific circle of latitude. Curves above and below that latitude will differ slightly in scale, but the graphic gives a rough indication of distance for the entire map.
Needless to say, I’ve spent far too many hours doing trigonometry lately. If ages pass before I see another formula with a cosine in it, I won’t be terribly upset. That being said, I don’t regret taking the time to do the necessary calculations. There are plenty of flat projection maps of the Forgotten Realms. As far as I'm concerned, having some new maps which showcase the curvature of Toril is a nice change of pace.