[OpenLayers-Users] TileCache and KaMaps

[Chris Holmes]

> In 1.2, metaTiling support does exist in TileCache. It's not extremely
> well tested yet. 

I tried it out and got results that were a bit off.

See: http://sigma.openplans.org/dev/test.html
vs.
http://sigma.openplans.org/dev/test-meta.html

The second uses metaTile for the tiger layers, the first doesn't, 
everything else is the same.  Overlaid on the bluemarble layer, however, 
everything in tiger is shifted south, the outlines don't match.  Not 
sure if there was something I configured wrong, but all I did was add 
metaTile=true.

When testing on its own it seemed to be working, definitely less 'United 
States' labels on my page.  So the root concept seems to be working, 
which is great news.

I'll also note that right now it seems to be having more blank images. 
It's not all pre-cached.  I've actually consistently had problems with 
areas that aren't pre-cached, they tend to not wait until the backend 
has returned, instead just return the broken images.  It would be great 
if I could get it so there's never the broken images, some just take a 
lot longer to load.

best regards,

Chris


It also doesn't hook directly into mapscript (and
> there aren't plans to, though it could in the future) to use added
> capabilities of MapServer like ka-map does. It also (due to lack of
> support in the Python Imaging library) doesn't support chopping up
> transparent tiles and maintaining transparency: this means that you
> can't metaTile transparent images.
> 
> TileCache is young. It hasn't been tested on dozens or hundreds of
> installs like ka-Map has been.
> 
> TileCache is written in Python. It doesn't require mapscript. It can be
> run on a service which is far from your original service (via WMS
> cascading). The code is clean. It runs under CGI or mod_python.  
> 
> TileCache supports multiple request formats. WorldWind, WMS-C, TMS.
> 
> TileCache supports multiple data backends: mapserver (via mapfiles), WMS
> cascading, mapnik, and is easy to extend to anything else -- for
> example, one of the next additions I'm going to look into is an ArcXML
> layer. This means that if you have a custom data source, it's probably
> easy for you to wrap it in TileCache. 
> 
> 
> TileCache is, for the most part, a replacement for ka-Map. However, it's
> an immature project, and may not fit all the needs that everyone has.
> The metaTiling support, in particular, is not extremely well tested, and
> that is the primary benefit that ka-Map offers. However, based on
> empirical testing, I feel that it's likely that for many cases,
> TileCache will be much faster than ka-Map, and I think that it's more
> likely to be maintained and extended in the future than ka-Map's
> rendering tool.
> 
> Personally, I'm working to migrate all my ka-Map based instances to
> TileCache. If TileCache doesn't do it, then my steps will be to make 
> TileCache do it, rather than setting up ka-Map. However, I have not yet
> migrated any projects which require metaTiling to TileCache, so I'm not
> yet convinced of its stability at that particular task. Anything which
> doesn't require metaTile support, I would absolutely recommend
> TileCache: I'm not to the same point with anything which requires
> metaTile support yet.  
> 
> Regards,

-- 
Chris Holmes
The Open Planning Project
http://topp.openplans.org
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