[OSM-dev] Projection calculation
wwalker at bybent.com
Tue May 13 15:32:47 BST 2008
I'm not using slippy map. For the project I'm doing I need static
images. I just can't sort out the math to find the veritcal position in
the tile map. I've tried mercator projection but I'm missing something.
without comments and with short var/function names I get lost.
Does anyone have a simple formula such that:
y = ....(lat)?
I've tried things like:
k = 4.0
y = log(tan(y*Math::PI/180.0) + 1/cos(y*Math::PI/180.0))/k
Which is the mercator projection formula (substituting 1/cos for sec)
Also tried a Miller cylindrical projection as that seems much more like
what the main tile looks like.
y = 1.25 * log(tan(Math::PI/4 + 0.8 * (y*Math::PI/180.0)/2))/miller
No joy there either.
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