[Tilesathome] Strange rendering of straight lines

[Matthias Julius]

Maarten Deen <mdeen at xs4all.nl> writes:

> I'm a bit puzzled for the reason why this gets rendered as it does:
> <http://informationfreeway.org/?lat=-84.951&lon=-144.66&zoom=12&layers=B0000F000F>

It looks really interesting.

>
> Tiles are
> <http://server.tah.openstreetmap.org/Browse/details/tile/12/402/4083/>
> <http://server.tah.openstreetmap.org/Browse/details/tile/12/402/4082/>
> <http://server.tah.openstreetmap.org/Browse/details/tile/12/401/4082/>
>
> In JOSM, this is a straight line. Why does the render mess this up so much?
> Two tiles have a turn in the coastline, and the middle tile is not in line with 
> the outer two.
>
> If you look in JOSM with the slippymap plugin, the rendering is way off of where 
> it should be.
>
> And the coast is riddled with these tiles.
> Is this some side-effect from being close to the pole?

I guess it is a projection error.  Those are always more visible at
higher latitudes.

Where do the coastlines get closer to where they should be?  At the
top, middle or bottom of the tiles?

Matthias