[OSM-dev] Re: [OSM-talk] Simple GD rendering

[Raphael Jacquot]

Oliver White wrote:
> Any other ideas on map projections to use?
> 
> As far as I can tell, there are certain properties that you'd like to have on 
> a map, and different projections each fulfil one or more of them:
>  * Accurate distances
>  * Accurate angles and small shapes
>  * Accurate areas
>  * Straight lines are straight on the map
>  * Lines of constant bearing are straight on the map
>  * Different map sheets fit together nicely
>  * Suitable for large areas
>  * Suitable for various locations around the world
>  * Doesn't disappear completely in certain areas (e.g. at high latitudes like 
> Mercator, or in the middle of the Isle of Man like OSGB)
>  * Doesn't go crazy around Norway (like UTM) or require special-cases (like 
> UTM at the poles)
>  * Easy to calculate, especially if you're doing it millions of times per map
> 
> Does anyone have particular favourites?  Personally I've found most of them to 
> be lacking in significant ways, but would be interested to know what's seen 
> as "a good idea" for street maps.

there's no such thing as "the perfect projection", it all depends on 
what is to be seen.

I'd say that for navigation, mercator is the most appropriate. it features :

* accurate angles and small shapes
* straight lines are straight on the map
* lines of constant bearing are straight on the map
also
* suitable for large areas (like, the world doesn't look like crap)

of course, it doesn't do
* accurate areas
* doesn't disappear in certain areas (the poles)... but..

* we don't really care about surfaces
* nobody from the group will ever go to either the north or the south 
pole ;D