[ka-Map-users] Overlays with dynamic information

Pg pg.navone at gmail.com
Fri Dec 30 05:52:58 EST 2005

Hello everybody. I'm doing some experiments on overlays and I will
appreciate comments and ideas.

My goal is to set up a map with some dynamic information, like traffic
events, road conditions etc. The dynamic info should be displayed on an
overlay and automatically refreshed even if the user doesn't reload the

Using the DrawingCanvas of kaMap, the wz_jsgraphics library and some ideas
and code circulated on this list I've written a module that fetch a server
side generated XML document with the points to draw on the overlay together
with rendering directives.
You can view an example in


The script is readable in
http://sistel.dyndns.info/ka-map/kaXmlOverlay.jsand it's tested in
Firefox only.

This is a partial solution to my problem, because it's limited to points,
while I would like to display also features as linestrings and polygons. As
isn't comfortable doing that with jsgraphics, I've implemented a solution
with a wmsLayer that (with some dirty hack) is reloaded periodically.
In the page


some streets are highlighted with different colours, and the highlight
should change more or less once a minute.

I'think this solution is not as good as the previous, because it's slow and
produce a very high load on the WMS server.
Better solutions could be:
  a. using jsgraphics to draw 2D features an make them scalable with the map
  b. using a server-side script to refresh the cache of a layer and convince
the browser to reload only that layer, ignoring the browser-cache

Have you any ideas about that? Is anyone working on that?

Bye and sorry for the long posting.

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