[OSM-dev] UK coastline borked

[Robert (Jamie) Munro]

Yann wrote:
> 
> 
> On 8/19/07, *spaetz* <osm at sspaeth.de <mailto:osm at sspaeth.de>> wrote:
> 
>     On Sun, Aug 19, 2007 at 06:28:48PM +0200, Jon Bright wrote:
>      > > - I think texts that are displayed but too small to be read
>     should be
>      > > hidden (look at London)
> 
>     I was concidering dropping the texts of towns and suburbs at z8. Of
>     course one can't read that. However, I kind of like the busy crammed
>     look that it gives, because if you leave that away, London becomes
>     just one word on the map. 
> 
> 
> Maybe it would make sense to tag towns with an approximation of their 
> population? That way we could emphasize bigger cities... and on low zoom 
> level tiles, say for example "display all towns > 50k people"...
> And with wikipedia's data that should be very easy to do :)

I don't think simple population is the right measure.

To take a stupid example, the "City of London" has a population of 
around 6000, but should probably be visible from about zoom level 4 (as 
it is currently on Mapnik). Meanwhile Westminster, next door, also a 
city, with around 30 times the population, shouldn't become visible 
until a much higher zoom, simply because it overlaps with London, which 
is more important. This is probably an exception because what should be 
labeled at level 4 is probably not the "City of London", but the region 
of London covered by the Greater London Authority, and traditionally 
centered on Charing Cross (which is actually in Westminster).

More generally, when looking at a relatively unpopulated area of land - 
say a desert, it's probably better to show even the tiniest village at a 
much higher zoom level, rather than show nothing at all.

Perhaps the algorithm is at each zoom level, sort the worlds places by 
size (or some other importance measure), then for each item on the list 
cross out all the other places within a certain radius (where that 
radius depends on the zoom), then work your way down the list, leaving 
the most important cities that are left.

Robert (Jamie) Munro