Quote Originally Posted by Alex View Post
I see. Well for me I'm doing a world map (would the continental scale be good?), but would like to have a scale for the full version and a scale for cut versions of let's say different continents. If that makes sense...?

Does the size of the map (canvas size) matter -- actually, I mean does it mess with the scale -- when it comes to scale?
Yes, obviously a larger physical map can cover the same extent ("Extent" is the area that a map covers) at a larger scale, or a larger extent at the same scale.


You should be aware that if you want to fit an entire globe into a map, you are going to run into problems. The larger the extent, the more distortion is involved in flattening the globe into a map. (What kind of distortion will depend on the way you flatten it. The ways of flattening a map are called "projections") With an unbroken map, any full world map is going to massively distort scale, and at least one of shape or area. If you want consistent scale, you will need a map with breaks in it (like when you peel an orange and lay it flat) The more breaks, the less distortion. The Interrupted Goode Homolosine and Dymaxion projections are well known examples of interrupted maps (http://en.wikipedia.org/wiki/Goode_h...ine_projection http://en.wikipedia.org/wiki/Dymaxion_map)

Also, the projections suitable for a full globe aren't at all suitable for a continent. This means you can't just crop a section out of a world map, scale it up, and add detail. The result will be distorted. There is software to convert between projections. NASA's G.Projector is one of the simpler ones, and is free and multiplatform, but it has the downside that any input into it must be in a particular projection (Equidistant Cylindrical) Other software can convert from most projections to any other projection, but it tends to be more complex to use. (I use QuantumGIS or GDAL myself)

Also, projection conversion can produce ugly results for "styled" maps or maps with labels. It's best to project raw data and then style it as needed for the particular projection.

Of course you can ignore all that and draw something that looks pretty and resembles a map. Sometimes something that looks like a map works just fine. However, if you want to get it right, so that you can do fun things like put your map on a 3d sphere you can rotate on screen, or if you just have a persnickety streak and want to do things correctly for the sake of doing them correctly, then it gets complicated, and it's the kind of thing you need to worry about at the beginning, not something you can slap on at the end as a quick fix.