[Tilesathome] Rendering of tiles with no nodes?

[Jiri Klement]

On Wed, Aug 13, 2008 at 11:00 AM, "Marc Schütz" <schuetzm at gmx.net> wrote:
>> I was wondering: how are tiles with no nodes but with a way across it
>> rendered? Are they rendered properly or will the be rendered empty?
>>
>> I'm asking because I requested tile 2872,1290 at z12 (and I believe I
>> requested it twice) and it comes back as empty. It has one railway running
>> across it.
>>
>> See the details at
>> <http://tah.openstreetmap.org/Browse/details/tile/12/2872/1290>
>>
>> Maarten
>>
>
> The client downloads a bounding box slightly larger than the tile. If a way crosses that bounding box but has no nodes in it, it is not returned by the API.

The downloaded area is actually quite big. 50% on left and rigt, 17%
on top and bottom. It means 2.68 times more data then necessary. The
area is bigger on left and right because there might be some caption
node just outside rendered tile with caption big enough to be part of
rendered tile.

One way I can think of how to fix this problem is process every new
node/way and save all z12 tiles the node/way is on. It would require
to parse stylesheets to find out which node is supposed to be rendered
as caption. Another issue are areas, which can be identified only
using stylesheets. There is no difference between closed way and area.

Another way migth be download only z12 tile area and when big
caption/long way is detected by renderer, save in database that the
node/way is partly on neighbouring tile.