[OSM-talk] Why place matters, slides from Vanessa Lawrence talk

[David Earl]

On 11/01/2008 11:48, Artem Pavlenko wrote:
>> Incidentally, this is exacerbated by the lazy rendering rule for Mapnik
> 
> What do you mean by 'lazy' rule?  AFAIK, all available hardware is 
> working hard day an night :)

I mean the way in which a tile isn't rendered until (after) it is looked 
at rather than proactively when an area changes.

>> - I was puzzled when someone said to me the other day "why is this
>> housing estate not connected to the rest of the road network?". It was;
>> but adjacent Mapnik tiles were inconsistent (both laterally and by zoom
>> level - and this wasn't a recently mapped area). You may not think this
>> matters, but I think this is a public face and it causes further
>> confusion and mistrust.
> 
> We can certainly improve here. Suggestions ?

I would try three things:

(a) Mapnik works on planet, yes? So perhaps use the planet diffs to 
determine areas which have changed and proactively mark all such areas 
dirty.

(b) for all dirty areas, render at all zoom levels (perhaps down to zoom 
12, like osmarender) and do the 8 immediately neighbouring tiles of 
dirty tiles as well for say zoom 13 or 14 and higher. (Many tiles, 
neighbouring tiles will be dirty anyway, so this amounts to adding one 
tile around each group of two-dimensionally contiguous dirty tiles.

(c) install updated tiles at one go so far as possible.

David