Berlin “dog’s head” line

In the early days of the Berlin Ringbahn (the city’s circular railway) the line was also called Hundekopf (dog’s head). Guess why… (isn’t it cute?)

The Geography of Wikipedia

Wikipedia celebrated its 10th birthday. So at the de-Wikipedia’s Kartenwerkstatt the idea came up to produce a couple of maps about the (meta-) geography of Wikipedia.

The first one shows the total count of georeferenced articles per square kilometer and also depicts the so called featured articles (excellent and worth reading).

The next map shows the growth of wikipedia articles from February to December 2010.

Extending GeoServer Styling with Geometry Transformations

While designing a map style, sometimes it is necessary to manipulate the geometries representation on-the-fly. For instance a straight line should be drawn as a sinuous line or plain building footprints should be decorated with a 3D effect. ESRI developers might be familiar with the various rendering extension interfaces in ArcObjects API.

With GeoTools/Geoserver there are similar extension points as well – although somewhat hidden. So here is a little sample for a custom geometry transformation function one can add to the GeoTools rendering module.

First create a java class that extends from org.geotools.filter.FunctionExpressionImpl and implement your geometry manipulation function inside the #evaluate method. If you need some examples, look at the existing classes that extend from FunctionExpressionImpl.

Second, to register that class to the GeoTools service provider interface: add a file named “org.opengis.filter.expression.Function” to the “META-INF/services” directory of your JAR file and add a line with the full class name of the java class (that one extending from FunctionExpressionImpl) to this file.

Third, create a JAR with your class and the META-INF and add it to the Geoserver’s classpath.

Fourth, create a SLD style where this new geometry function is used:

  <FeatureTypeStyle>
    <Rule>
      <PolygonSymbolizer>
        <Geometry>
           <ogc:Function name="magic">
              <ogc:PropertyName>the_geom</ogc:PropertyName>
              <ogc:PropertyName>bld_height</ogc:PropertyName>
           </ogc:Function>
        </Geometry>
        <Stroke>
          <CssParameter name="stroke">#888888</CssParameter>
          <CssParameter name="stroke-width">0.6</CssParameter>
        </Stroke>
      </PolygonSymbolizer>
    </Rule>
  </FeatureTypeStyle>

Voilá… oh I forgot to say, that of course you can pass other attributes from the feature to your function class – like with my example the attribute “building height” to control the height of the 3D wire frame.

Journal of Spatial Information Science

There is a new open access journal about spatial information science called Journal of Spatial Information Science, which adopts an open peer review process. The journal aims to publish research spanning the theoretical foundations of spatial and geographical information science, through computation with geospatial information, to technologies for geographical information use. The first issue has some really interesting articles.

80 percent is not enough

If you are somewhat familiar with the GIS stuff, most likely you’ve heard about that gullible, urban-legend-like qoute that 80% of all data has spatial reference. It’s omnipresent in GIS product brochures and company ads – even though its empirical foundation is, hmm lets say …dubious.

However, I was somewhat astonished when I read this article in Computerworld, whereto: “..95% is more accurate today”. Do I hear 105%? Somewhere? Oh and by the way, did you know: 95% of all food contains water.

Why do we need a Smart Grid?

Still scratching your head over what the COP15 fuss was all about? I hope, next year they’ll start thinking about smarter stuff that will really help to solve future problems. Smart Power Grids is such a thing and I wonder why it is discussed so little at the political arena here in Germany.

You might want to have a look at these two intelligent videos from Peter Batty of Enspiria about why we need Smart Grids and the technology behind it.