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

Tom Hughes tom at compton.nu
Wed Feb 4 12:39:21 GMT 2009

Matthias Brandt wrote:
> Tom Hughes wrote:
>> Matthias Brandt wrote:
>>> 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.
>> Did you have an alternative value in mind?
> Not really. But I would like to know, if there is any reason for this. 
> I'm writing my Bachelorthesis about OpenStreetMaps and I would like to 
> explain this bound.

Well it's essentially arbitrary, and the reasons that you quoted seem 
reasonable enough for an arbitrary bound.

If what you're asking is why it doesn't just go to 90 degrees then you 
might want to consider what happens to the projection function in the 
limit as the latitude approaches 90 degrees...


Tom Hughes (tom at compton.nu)

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