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Sometimes it is useful to abstract away the repetitive layer creation code with a configuration-based approach. For example consider this very simple map taken from the OpenLayers examples : How could we avoid repeating invoking the layer contructor and instead provde a framework that allows us to instantiate any layer with just configuration? The solution is quite simple.

I have been playing with TileDrawer recently. After a first rapid successful test on a throw-away EC2 instance I decided to deploy one on a vm for intranet use. The installation process is pretty straightforward, just run the script copied from the TileDrawer page as root. FYI make sure you have installed curl and python-cssutils before launching the script. After the script completed I started browsing the map and noticed that tiles took a looong time to render. A look at top from the server console showed that postgres was hogging the cpu. Memory was fine with no signs of swapping (it is a 1GB instance which I promptly upgraded to 2, running on server class hardware with Xeon CPU). Even after the memory upgrade tile rendering was so slow that the browser would sometime give up and show a white tile. I decided to look into it a little further and started by using the technique I have already described in another article . The database cache looked fine though as mo...

Sometimes it is convenient to make certain topological operations available in a web-based gis. For a gis that makes heavy use of Javascript (like OpenLayers-based ones) it might be worth looking at jSTS , a Javascript port of JTS. For all the rest and for those who don't want to load yet another library in the browser you can always write a Grails controller that encapsulates common JTS operations like buffer, intersection, union, etc. Assuming you are familiar with Grails the steps are as follows: drop the jts jar in the lib directory create a controller and define the relevant methods define a url mapping to prettify the calls Step 1 is trivial, so we'll go straight to 2. Create a controller and call it JtsController , then open the source file and paste this code: import com.vividsolutions.jts.geom.* import com.vividsolutions.jts.io.* import com.vividsolutions.jts.operation.overlay.snap.* import grails.converters.JSON import grails.plugins.springsecuri...