[OSM-dev] Y-Boundary of Mercator-Projection

[Matthias Brandt]

Hi,

i've searched the archive of this mailinglist and the wiki about the 
magical y-boundary set to 85.05113° (respective 180° projected) in the 
Mercator Projection.

The Wiki says [1]:
 > By using this bound, the entire map becomes a (very large) square.

Is this the only reason for this afficial bound? To have a square 
instead of an rectangle?
And the reason "Google is using it, too" is not a really good 
explanation for me...


Matthias

[1] http://wiki.openstreetmap.org/wiki/Slippy_map_tilenames#X_and_Y