[OSM-dev] Projection Issues

[Lars Aronsson]

Christopher Schmidt wrote:

> The problem here is that OSM's setup right now depends on two
> contradictory ways of dealing with data: 
>  * Mercator projected
>  * Unprojected/EPSG:4326
> 
> There are several possible ways to fix this.

Many million years ago, a meteorite landed in central Sweden, 
causing this perfectly circular ring of lakes,
http://www.openstreetmap.org/index.html?lat=61.033&lon=14.928&zoom=8

On OSM's map (and Google Maps) that actually looks like a circle,
http://maps.google.com/maps?t=h&ll=61.033,14.928&spn=.5,.5&om=1

On your own map, http://crschmidt.net/mapping/openlayers/osm
that oval looks twice as wide as it is high.  (Sorry, I don't know 
how to link to a specific coordinate there.)

It's your projection that is broken, not OSM's.  (Well, OSM's and 
Google's projection is broken too, as it erroneously presents 
latitudes as straight lines and longitudes as parallels, but this 
only matters in really small scales.)

>  * Stop with the Mercator Madness :) And start using Unprojected
>    coordinates. This would probably simplify a lot of math all over,

Duh!  Google Maps did that mistake in its first two weeks, but 
they were pretty fast to fix it.  People looking at the satellite 
image of a well-known sports arena want it to be oval in the right 
direction, not in the perpendicular one.  If a roundabout is 
circular in reality, it should be so on the map.  More than half 
of Sweden, most of Norway, and virtually all of Finland, is north 
of 60 degrees and cosine(60) = 0.5


-- 
  Lars Aronsson (lars at aronsson.se)
  Aronsson Datateknik - http://aronsson.se