[OSM-newbies] Squashed Display (Not JOSM)

[Stewart C. Russell]

Hi Matthew,

> Is there some extra math I'm supposed to employ to display lon/lat
> coordinates beyond just scaling them to the dimensions of the display?

You do have to account for the earth's curvature.

If I understand correctly, you're scaling each degree of latitude and
longitude to a fixed distance on the page, right? That will compress
coordinates at the extreme edges, but it's still a valid map.

You can also map each linear metre on the ground to a set distance on
the page. This turns gridded cities properly rectilinear, but only works
over short distances. The earth's curvature starts to distort lengths
near the edges.

Here's a short article that gives a quick overview of the OSM tile
projection:
http://alastaira.wordpress.com/2011/01/23/the-google-maps-bing-maps-spherical-mercator-projection/


cheers,
 Stewart