WMS-performance

Permanently deleted user

22. Juni 2011 14:19

I'm currently trying to add a few external WMS's to my Geocortex Essentials site. I can add them and everything is working just fine. However (and it's a big however) the WMS's have a load time of around 15 seconds. This is quite frankly too slow; I know there is nothing wrong with these WMS's and the problem must lie with Geocortex Essentials. I was therefore wondering if there was any way I could tweak these WMS's within the Define Map Resources window or anywhere else?

n.b. The site I'm making will act as a pooling centre for a considerable number of WMS's from different organizations in Norway. An example of our existing map can be found at www.gislink.no.

Thanks

James

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  Jeff Siemens

  22. Juni 2011 23:03

  Hi James,

  Which type of viewer are you using?  Flex, Silverlight, ADF, JavaScript?

  In order to troubleshoot the issue, it may be worthwhile to monitor the HTTP traffic coming from the viewer to the WMS.  Take one of the requests and just enter the URL into a browser and see how long it takes to draw (clear the cache first of course).  Take a look at the parameters on the URL string to see if anything is amiss.  Maybe, for example, the services are being reprojected and that's causing a performance hit?

   

   

  Jeff

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  Permanently deleted user

  16. September 2011 02:39

  I wouldn't think this is a Geocortex issue per se.  WMS Performance is terrible when you append it to Tiled Cache Styling Client Browsers.

  One has to consider what WMS is.  Maybe the hope is to be able to connect to WMTS Services.  That would a huge boost in performance.

  The composition of WMS is for the client browser to send the extents to the WMS Service, the server then generates the corresponding image, and sends this image back.  The client has to download potentially a large image (the size of your browser view: JPEG = ~140k, PNG = ~1.6MB), and display it.  When the viewer's extent or zoom level changes, the browser will perform the above action again to update the view.  This is also dependent on the image format you request (PNG or JPG).  So this is a huge consideration.

  Now if we talk about WMTS (Web Map Tile Service), they are usually zoom levels, image pyramids, and set image size.  256x256 JPEG = ~25kB, PNG = ~120kB.  The server usually has these layers preprocessed, so the only effort is to download the image.  But this also means that there will be multiple requests to this server to fill the browser view.  So the drawback to this kind of system is if the client browser is accessing multiple WMTS services (let's say 5), you can potentially request up to 100 requests.  (1024x768) (5x4 = 20 Tiles) = 100 requests.  The benefit with WMTS, is usually the browser will cache these images, such that it can bring these images back up when the zoom level and tile has been requested before.

  Conclusion:

  To get good performance, you need to consider your bandwidth to that server and image request format: JPEG will definitely bring you faster downloads and responsiveness.  This will also depend on the size of the viewing area.

  Hope this give you some insight into the WMS and WMTS

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