Archive for the 'WPServer' Category

Updates to WPServer Demo

Posted in Locality and Space, OpenLayers, WPServer on October 6th, 2007 at 12:27:32

The WPServer demo is more complete now: WPServer Demo.

New functionality:

  • More operations
  • Control over size of buffer
  • Control over tolerance of simplify
  • Ability to select specific features to operate on
  • More complete set of OpenLayers Feature editing tools

Note that everything here is included in the stock version of what will be OpenLayers 2.5. All the code that you need to set the client up is displayed in the web page — there’s no magic behind it.

There is one additional thing to note: The demo now has the ability to load features from the FeatureServer demo. This is one of the most important things about working over the web: the various pieces of data that exist in disparate data sources can be integrated.

Unfortunately, this is made harder than it should be because of the limitations of the browser. For security reasons, it is not possible to load data from any URL on the web: in this case, the WPServer ‘noop’ (no operation) is used essentially as a GeoJSON proxy, fetching the features from FeatureServer to bring them into the local javascript domain, where we can fetch them. However, once that proxy is set up, we can fetch data from multiple locations, and put it together on the client, creating new features from the old, and taking them out to put them wherever we like.

Note that although this demo uses GeoJSON extensively — it’s the only language WPServer speaks at the moment — there’s no reason for that to be the case. OpenLayers has the ability to load data from WFS, as well as the ability to load other things like KML documents. You can load these datasources into the same layer, and use the WPServer functionality to put things together.

Want your shapefiles on a map? Use FeatureServer. Want to buffer each of the points in your FeatureServer-served data? Serialize them, and pass them up to WPServer, then display the data that comes back. Want to mix in KML data, to see the intersections? Add a KML layer to OpenLayers, and use WPServer to do the intersections.

… Crap. I think what OpenLayers can do now might actually be something people would refer to as GIS.

Geo Processing Over the Web

Posted in Locality and Space, OpenLayers, WPServer on October 4th, 2007 at 23:54:37

There’s a couple of different efforts going on to do web processing over the web — in an effort to understand what it’s all about, I put together a little web processing server and a demo to go along with it.

WPServer Demo

Using OGR and the GEOS operators built into it, it allows one to do operations I’m told are common: buffering, centroid, convex hull, and dissolve.

The source for these operations is simple: as few as 8 lines to define your own operation, as the OGRGeos operators and the Shapely buffer operation show.

The Boston Routing Demo is also now using WPServer to do its routing, via the PGrouting action.

Although WPServer shares an acronym with OGC’s WPS, it doesn’t yet implement WPS — however, like FeatureServer, it has a pluggable frontend architecture for determining the types of actions to perform… but only REST + GeoJSON are supported so far :)

I think it’s a pretty looking demo, even if I’m not sure if it’s useful at all.