[Tilesathome] Lowzoom Place Labels displaced

[Rob Reid]

Frederik Ramm wrote the following on 18/09/2008 18:46:
> Hi,
>
>     I have somehow lost overview over the lowzoom process. A user has 
> reported displaced placenames on t at h z11 to me:
>
> http://informationfreeway.org/?lat=50.47202017317468&lon=7.795465134494669&zoom=11&layers=B000F000F
>
> The label offset is about 10km north(-east-ish) in the whole area.
>
> Is this still normal behaviour (I know we used to have projection 
> issues), or should this have been fixed in the mean time?
>   
I'm still seeing projection problems with or/p in lowzoom as well.
See 
http://lists.openstreetmap.org/pipermail/tilesathome/2008-August/003086.html 
for when I reported it.
Down around NZ the offset appears to be south rather than north.
I'm have not done any testing on it but I suspect it seemed to start 
appearing about the time the op/p proximity filter was added.
> Also, the same user reported some white squares on zoom levels 11 and 
> smaller, which seem to be lowzoom artifacts. Can I tell him to just go 
> to z8 on informationfreeway and hit "r", or what is the current 
> established procedure to either update a lowzoom tile yourself or 
> request that someone else do it?
>   
I have not seen white squares but i have seen black squares which could 
be related and was caused by a client bug relating to blank z12 blank 
tiles handling,
see 
http://lists.openstreetmap.org/pipermail/tilesathome/2008-August/003457.html
The affected tiles look ok at zoom 12 but any lowzoom based on them is 
faulty.

Lowzooms  for z6-11 are currently done by the server based on z12 
changes and I think are done approximately daily so the best way to 
trigger one is to request a re-render on a z12 tile and then wait for 
that to trigger the lowzoom.
The caption layers used to produce lowzoom are still generated manually 
by clients though so if you see a problem with captions you need to 
regenerate the captions manually and upload before trying to trigger the 
lowzoom.

rcr