[OSM-talk] Mapnik at zoom=19

[Kai Krueger]

Frederik Ramm wrote
> Hi,
> 
> On 13.01.2013 21:23, Gervase Markham wrote:
>> Did we ever do z=19?
> 
> To my knowledge, no.

I am also reasonably sure z19 never existed. Osmarender only used to go to
Z17 and so mapnik had one zoom level more than osmarender, but neither went
further than z18.


Frederik Ramm wrote
>> Did we stop because it's a load more disk space, or
>> something like that? If not, could we consider it?
> 
> Given that very few areas are going to be even looked at at z19 I 
> suspect the additional disk space used would not amount to much.

Over time, the usage would creep up, but one could be fairly aggressive on
deleting cached files for z19. Z19 tiles are most of the time reasonably
easy to handle with rendering on the fly so a higher cache miss ratio would
matter less.

Of cause that would put extra pressure on the renderer, but during normal
operations (i.e. if it is not e.g. rerendering everything) it seems to still
have a fair amount of capacity left.

Also the tile throttling mechanisms seem to work sufficiently well to
prevent any "crazy" people from e.g. trying to download all of Europe at
z19.

So my guess would be that the current server has the resources to deal with
z19 although it would cut into spare capacity for handling future growth. 


Frederik Ramm wrote
>  But the 
> style sheet we're currently using doesn't lend itself well to extension 
> beyond z18, it would require some tweaking. Nothing big though.

Imho, the current style sheet, if not perfect, at least works for z19 so I
think one could just use it to begin with and then improve it through the
normal stylesheet improvemet process.

There are by now enough densely mapped areas, where a z19 level offers a
real advantage. At z18 too much information gets dropped in the decluttering
process. 

At the moment, when I want to e.g. check if  something is already mapped in
a densely mapped area, I need to switch into Potlatch where I can zoom to
z19 (and beyond). However, if everyone does that, I suspect that would use
up much more resources than offering a z19 rendered map.

Therefore imho, offering z19 would be possible and a net benefit to OSM, but
that is obviously for the server admin team to decide.

Kai



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