[ka-Map-users] evaluating ka-Map

David Bitner osgis.lists at gmail.com
Fri Sep 9 14:39:21 EDT 2005

The issue isn't that grabbing the WMS would be all that much of a 
performance hog, the issue is that ka-map relies on caching the tiles that 
it uses. You will not need to write the WMS to a static file, and that 
really wouldn't help you at all. For something like real-time weather, you 
could set up a cron job that cleared the cache out every so often, otherwise 
ka-map would be calling up the cache of old information even when there is 
new information available. Along with this, you would have a performance hit 
because you would constantly be making calls to mapserver and the WMS rather 
than just a call to a cached image.


On 9/9/05, Nate Reed <nate at seastar.jpl.nasa.gov> wrote:
> Good points, Charlton. I can see we might need to setup a regular cron
> job to grab recent images from our WMS and write them to a static file
> which ka-Map can then consume, and we do need to a way to expire tiles.
> Probably could just force the page to reload with some JavaScript or
> META tags?...
> On Fri, 9 Sep 2005, Charlton Purvis wrote:
> > Hey, Nate and Paul:
> >
> > > Just so I understand, is this because of the cost of loading all the 
> tiles
> > > when a layer is toggled on/off, or does it use some kind of 
> optimization
> > > that depends on static files?
> >
> > Nate, I've been playing around w/ ka-map lately, and it really is slick.
> > Paul, please correct me if I'm wrong . . .
> >
> > If you're serving up a layer via ka-map that is really a WMS layer from
> > another box, I *think* that ka-map will make n-WMS queries where n is 
> the
> > number of tiles in your given view. In other words, I don't *think* that 
> it
> > makes one WMS query and then divides that image up into tiles. If that 
> is
> > the case, then a dependence on a foreign WMS layer might be tricky
> > performance-wise.
> >
> > The other question I have is: Assuming that WMS is OK and that what I
> > assumed above is way off base, what happens if the WMS layer is real 
> time
> > weather stuff like Nate is using? Wouldn't it only query the WMS once to
> > create the tiles = no real time update w/o doing something fancy on your 
> end
> > to either clear those from the cache on the hour or tag some kind of
> > temporal index to each tile?
> >
> > Thanks, Paul, for such a dynamite product in such a short period of 
> time.
> >
> > Charlton
> >
> --
> Nate Reed
> Physical Oceanography DAAC
> Jet Propulsion Lab / Raytheon ITSS
> (626)744-5528 nate at seastar.jpl.nasa.gov
> _______________________________________________
> ka-Map-users mailing list
> ka-Map-users at lists.maptools.org
> http://lists.maptools.org/mailman/listinfo/ka-map-users
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