[OSM-talk] Projections

[Andrew Rowbottom]

>Are you trying to say that there is a standard for tiling in Mercator
>projection written down somewhere, and we are breaking it?

The big issue here is that the program used to display the tiles must
know the projection used if it wants to convert pixel coordinates (or
tile names) to lat/long. The current implementation assumes a
particular conversion that is not the same for all the different sets
of tiles.



Something to remember is the difference between (I\'m a big vauge on
the terminology here)

A Geographic Coordinate system (lat/long) which usually attempts to be
a closeish match to the real world (spherical or ellipsoid or
whatever).

and

a projected Coordinate System which distort lat/long in a GCS to
arbitrary locations on a \"flat\" surface.

Both are relevant, though the differences between most GCS\'s is
usually less than 1km (equivalent on the surface of the earth).

PCS\'s cannot help but be different e.g. Peters projection, mercator,
orange peel etc. Which one you use is only a matter of choice. There
is no one true projection.

I\'ll say that again.

There is no one true projection.

Andrew Rowbottom

p.s. apologies if someone has already replied with similar content.