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.<br>
<br>
David<br><br><div><span class="gmail_quote">On 9/9/05, <b class="gmail_sendername">Nate Reed</b> <<a href="mailto:nate@seastar.jpl.nasa.gov">nate@seastar.jpl.nasa.gov</a>> wrote:</span><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
Good points, Charlton. I can see we might need to setup a regular cron<br>job to grab recent images from our WMS and write them to a static file<br>which ka-Map can then consume, and we do need to a way to expire tiles.<br>
Probably could just force the page to reload with some JavaScript or<br>META tags?...<br><br>On Fri, 9 Sep 2005, Charlton Purvis wrote:<br><br>> Hey, Nate and Paul:<br>><br>> > Just so I understand, is this because of the cost of loading all the tiles
<br>> > when a layer is toggled on/off, or does it use some kind of optimization<br>> > that depends on static files?<br>><br>> Nate, I've been playing around w/ ka-map lately, and it really is slick.<br>
> Paul, please correct me if I'm wrong . . .<br>><br>> If you're serving up a layer via ka-map that is really a WMS layer from<br>> another box, I *think* that ka-map will make n-WMS queries where n is the<br>
> number of tiles in your given view. In other words, I don't *think* that it<br>> makes one WMS query and then divides that image up into tiles. If that is<br>> the case, then a dependence on a foreign WMS layer might be tricky
<br>> performance-wise.<br>><br>> The other question I have is: Assuming that WMS is OK and that what I<br>> assumed above is way off base, what happens if the WMS layer is real time<br>> weather stuff like Nate is using? Wouldn't it only query the WMS once to
<br>> create the tiles = no real time update w/o doing something fancy on your end<br>> to either clear those from the cache on the hour or tag some kind of<br>> temporal index to each tile?<br>><br>> Thanks, Paul, for such a dynamite product in such a short period of time.
<br>><br>> Charlton<br>><br><br>--<br>Nate Reed<br>Physical Oceanography DAAC<br>Jet Propulsion Lab / Raytheon ITSS<br>(626)744-5528 <a href="mailto:nate@seastar.jpl.nasa.gov">nate@seastar.jpl.nasa.gov</a><br><br>
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