Today I’m going to show you how to achieve those effects dynamically using what we call geometry transformations. Geometry transformations are yet another extension to SLD in order to make it more powerful. (Another example of SLD an extension that GeoServer has implemented is dynamic symbolizers.) Standard SLD allows the user to specify a <Geometry> element in each symbolizer, but its contents can only be a <PropertyName>; this allows a user to choose a different geometry should a spatial table contain more than one. With geometry transformations, GeoServer allows you to specify a filter function as well, which can transform the geometry. (You may want to refer to my previous post on filter functions.)

Let’s look at an example. Say we have a building layer, rendered with a plain gray fill:

We can add a twist to this plain map by adding a drop shadow beneath the buildings layer. To achieve this we will offset the buildings a bit, fill them dark gray, and then paint the standard buildings layer on top of it. The style looks like:

      <FeatureTypeStyle>
        <Rule>
          <Title>Shadow</Title>
          <PolygonSymbolizer>
            <Geometry>
               <ogc:Function name="offset">
                  <ogc:PropertyName>the_geom</ogc:PropertyName>
                  <ogc:Literal>0.00004</ogc:Literal>
                  <ogc:Literal>-0.00004</ogc:Literal>
               </ogc:Function>
            </Geometry>
            <Fill>
              <CssParameter name="fill">#555555</CssParameter>
            </Fill>
          </PolygonSymbolizer>
        </Rule>
      </FeatureTypeStyle>
      <FeatureTypeStyle>
        <Rule>
          <Title>Polygon</Title>
          <PolygonSymbolizer>
            <Fill>
              <CssParameter name="fill">#CCCCCC</CssParameter>
            </Fill>
            <Stroke>
              <CssParameter name="stroke">#000000</CssParameter>
              <CssParameter name="stroke-width">0.5</CssParameter>
            </Stroke>
          </PolygonSymbolizer>
        </Rule>
      </FeatureTypeStyle>

And the result is:

The filter function takes the geometries and offsets them by (0.00004, -0.00004). Geometry transformations occur against the original geometry, which in this particular case is in EPSG:4326, so the values of the offset are also in units of lon/lat.

You can find more examples about this functionality in the geometry transformations section of the User Manual. You can also get creative by looking at the currently available set of filter functions. Also remember, if you want a function that’s not there, it is possible to add new ones; drop by on the developer mailing list and we’ll provide you with directions.

Let’s have a look at an example. Below is a map drawn by GeoServer that is reprojected to a projection that happens to sit across the dateline, the usual “edge” of the map. As you can see the reprojection is not doing a good job where the dateline is crossed:

Polygons crossing dateline change before improving the renderer

However, GeoServer now has what is called advanced projection handling. With this enabled, the dateline wrapping is properly handled and, in addition, the map repeats in a continuous fashion:

Polygons crossing the dateline with advanced projection handling

For more information, including how to turn on this (optional) feature, please see this post from GeoSolutions.

If so, welcome to the club. One thing few people know is that both SLD and WFS filtering capabilities can be extended by using filter functions. A filter function is just like a programming language function, it’s something that takes arguments and returns some result. For example, “sin(toRadians(45))” will compute the mathematical sin of 45 degrees, and “strSubstring(”hippopotamus”, 0,  5)” will return “hippo”.

The concept of filter function is standardized, but functions themselves are not, so once you start using them you’re tied to a specific server. However they often provide the level of flexibility that you just need in order to get some work done. The good news is that GeoServer already contains tens of them, from number and date formatting, to geometry manipulation, math, string wrangling. So far we just never found the time to document them, but things have changed and we have now quite a complete reference along with some examples.

Let me show you a simple example of using functions. Say we have a contour map, each isoline has an elevation, and we want to show it on the map. Unfortunately the elevation is stored as a floating point, resulting in a less than pleasing output of “150.0″ or sometimes “149.999999″ when we know the elevation accuracy does not go beyond the meter. To get nice labelling we can use the “numberFormat” filter function to force an integer representation instead (along with some VendorOptions):

<TextSymbolizer>
  <Label>
    <ogc:Function name="numberFormat">
       <ogc:Literal>#</ogc:Literal>
       <ogc:PropertyName>ELEVATION</ogc:PropertyName>
    </ogc:Function>
   </Label>

  ....

   <VendorOption name="followLine">true</VendorOption>
   <VendorOption name="repeat">250</VendorOption>
   <VendorOption name="maxDisplacement">150</VendorOption>
   <VendorOption name="maxAngleDelta">30</VendorOption>
</TextSymbolizer>

Notice how the the ELEVATION field is formatted as an integer number following the simple formatting pattern provided (for a full reference see the the Java DecimalFormat documentation):

I hope you’ll find interesting and clever uses of the existing filter functions to improve the way you work with GeoServer. Next time I’ll show you my favourite one, which is also a new feature in GeoServer 2.0.1, called “geometry transformations”. Stay tuned to learn more about it.

Note that by applying the patch the same rules as described here apply. Users will have to either update systems that rely on anonymous access via GET operations or alternatively configure the security subsystem to allow them.

Recently the issue of security has come up with regards to the restconfig plug-in. Essentially it boils down to the fact that GeoServer allows anonymous access to any resource or service when the HTTP request method is GET. In the case of restconfig this can make sensitive information available anonymously such as database connection parameters which can contain passwords and the like.

To remedy this situation in 2.0.1 the GeoServer security subsystem has been extended to allow for configuring access to RESTful services. This is documented in the user guide.

The major caveat for users upgrading to 2.0.1 is that any systems that depended on the previous behavior of allowing GET access to resources without authentication will undoubtedly break. In this case users have two options:

1. Start supplying administrator credentials with all requests
2. Reconfigure GeoServer to allow for anonymous access for GET operations

A patch has been created for 1.7.x users as well.

Try it out. Please report any issues to the GeoServer users list. Thanks for using GeoServer!

Possibly the most significant change since 2.0.0 has been the addition of the RESTful API to the security sub system. Previously, users were able to connect in a read-only capacity to otherwise secure services through RESTful GET requests. While this is a good fix for GeoServer, it does mean that users who were previously relying on anonymous read access to secure services must now authenticate before they can access them. More details are available for those who are interested.

Other changes include usability changes to the administration UI, an updated Windows installer that now contains service and console installation options, and over 100 other issues fixed.

We encourage you to download the latest version and take it for a spin and report any issues you encounter to the mailing list or bug tracker.

As always, we owe a debt of gratitude to all those that have contributed bug reports, fixes, patches and features. A special thanks goes out to LISAsoft for managing this release.

CSIRO is Australia’s national science agency.

As advertised on seek.com.au:

Senior Software Engineer – Leading Role
http://www.seek.com.au/users/apply/index.ascx?Sequence=39&PageNumber=1&jobid=16484299

Software Engineers – 5 Positions
http://www.seek.com.au/users/apply/index.ascx?Sequence=72&PageNumber=1&jobid=16484529

Software Engineer – Administrator
http://www.seek.com.au/users/apply/index.ascx?Sequence=56&PageNumber=1&jobid=16484057

The same positions on the CSIRO recruitment website:

Positions Details – 2009/995 – Senior Software Engineer – Leading Role
https://recruitment.csiro.au/asp/job_details.asp?RefNo=2009%2F995

Positions Details – 2009/996 – Software Engineers – 5 Positions
https://recruitment.csiro.au/asp/job_details.asp?RefNo=2009%2F996

Positions Details – 2009/994 – Software Engineer – Administrator
https://recruitment.csiro.au/asp/job_details.asp?RefNo=2009%2F994

Applications close on 10 January 2010. These are fixed-term positions of approximately 18 months (term end 30 June, 2011).

The positions will be based at the Australian Resources Research Centre, 26 Dick Perry Ave, Kensington WA, Australia. This is in an inner suburb of Perth, Western Australia.
http://maps.google.com.au/maps?f=q&source=s_q&hl=en&geocode=&q=26+Dick+Perry+Ave+Kensington+WA&sll=-31.993227,115.885849&sspn=0.969029,2.073669&ie=UTF8&hq=&hnear=26+Dick+Perry+Ave,+Kensington+Western+Australia+6151&ll=-31.994847,115.884718&spn=0.242253,0.518417&z=12

Street view:
http://maps.google.com.au/maps?f=q&source=s_q&hl=en&geocode=&q=26+Dick+Perry+Ave+Kensington+WA&sll=-31.993227,115.885849&sspn=0.969029,2.073669&ie=UTF8&hq=&hnear=26+Dick+Perry+Ave,+Kensington+Western+Australia+6151&ll=-31.995238,115.885892&spn=0.001893,0.00405&t=h&z=19&layer=c&cbll=-31.995244,115.8861&panoid=-fbF3xYlc6_RMyuiOUPYMQ&cbp=12,356.75,,0,5.95

http://yourserver/geoserver/wms?REQUEST=GetMap&...&TIME=2009-12-12,2009-12-13&...

You can get some more details on the GeoSolutions blog.

Supporting a project such as GeoServer requires a great investment of time and resources. Organizations that support it are faced with the problem of finding funding. As founder of my own company, I often find myself in the position to seek funding for supporting GeoServer and I obviously tend to prefer large contracts to small ones. This seems perfectly reasonable, however I do recognize that in the long run this approach may cause some missed opportunities. Large funding usually focuses on large developments, but they leave aside common glitches and bugs, i.e. isolated features that are not working properly or could be improved relatively easily. To counter this, supporting organizations must invest surplus money and resources from other contracts into tackling these problems, since it is difficult or inefficient to chase money to address each small issue separately.

As a specific example, I have lately seen people struggling to get the ImagePyramid extension working, and I know it would be relatively easy to improve things (in that it would not need a lot of funding) but none of our current clients needs this functionality, so the work never gets done.

With this in mind, I have come up with the following idea: once someone, be it a user or a support organization, recognizes an issue/missing feature that no one else wants or has funding to fix, we should try to describe the problem/feature somewhere (such as on this blog), provide a Point of Contact (POC) for the work and then ask the community for an Expression of Interest (EOI) to check whether there is enough momentum/desire to fix/implement. Perhaps the POC should write the proposal having already scoped out the work or maybe the scope should wait until we know that there is enough interest. Another topic where I would see some interest is in whether the process should be completely transparent or not regarding who gives the funding as well as who spends the funding gathered. I would be interested in feedback on all of these suggestions.

To test his idea, I would like to invite anyone who might be interested in providing a bit of funding to improve the support for the ImagePyramid extension in GeoServer to express your interest to me. Specifically, I am talking about automagic import from GDAL retile, improved stability and performance, and/or automagic pyramiding as a GeoServer/GeoTools utility.

If you are interested you can drop me an email at simone.giannecchiniATgeo-solutions.it.

Ciao, Simone.