[ka-Map-users] ka-Map and OpenLayers

[Robert Thau]

Paul Spencer writes:
 > Good point ... we were discussing tiling today.  I can actually see  
 > ka-Map turning into a tile-cache server project separate from  
 > OpenLayers.  The shortest path to integration is to add a kaMap layer  
 > and tile class to OpenLayers and use the existing kaMap tile.php to  
 > serve tiles to it.  I'm currently working on designing a better  
 > strategy for tile caching since the current directory structure is  
 > very limited for large caches (it only goes one directory deep when  
 > you really look at it).

One thing that might be useful to look at is the Rails caching strategy.
Which actually relies on a dirty trick:  

Rails registers itself with its host webserver as a 404 (file not
found) handler.  So, when a request is made for a cacheable item, the
webserver first tries to read it as an ordinary file.  If such a file
is present, it gets served normally, like any other static file, and
no dynamic code of any kind (Ruby or otherwise) is invoked.  If not,
then Rails is invoked --- and if the item is cacheable, it stores the
data it's serving in a file, for the host server to serve normally
next time.

The approach has been tried at least once for map tiles --- see

   http://www.ivygis.org

for an example and downloads.  The code implementing tile generation
is in these files:

   .../ivygis_engine/app/models/abstract_tiler.rb
   .../ivygis_engine/app/models/image_tiler.rb
   .../ivygis_engine/app/controllers/tile_controller.rb

The 'controller' is the code that responds directly to web requests;
the 'tiler' classes do tile generation.

(Also on display: a prototype-based map tile layer which also displays
polygons using SVG or VML, if the browser supports one or the other...).

Hope this is of interest...

rst