Hi all

Apologies if this post if off topic. This seems to fit under the scope of KML tool.

This is a heads up to say that I've nearly completed a first version of a KML output module GeoServer (the OGC WFS reference implemeations). What does this mean? In short it allows for the production of KML from any format supported by GeoServer (well actually by GeoTools the library behind GeoServer).

This includes Shapefile, MIF/MID, OracleSpatial, PostgreSQL (PostGIS), VPF, Tiger, MySQL and a fair few more.

You can see a screen shot and the KML file itself at the end of this post.

Note that the KML file crashed on my friends Google Earth so I would appreciate feed back from people to let me know if it does / does not work.

The styling is random for now, but GeoTools has a full expression based styling language so expect a range of thematic (electoral, population, poverty...) and cartographic maps in the near future once that is completed.

If anyone is familiar with GeoServer and wants to try this on their own data let me know, installation is a bit tricky for now as I had to patch the core GeoTools GML producer to handle some of KMLs quirks (I'll write them up in another post if anyone is interested)

I plan eventually to put out a stand alone tool so that you won't need GeoServer, probably as a plug in to uDIG. The downside to that is that you won't be able to use the new networking capabilities of Google Earth to pull in live data.

So, cheers to July the 4th, its amazing what you can do with a day off!

Lots still to do, and some refactoring before I'm happy to commit this to the GeoServer code base, but I welcome comments suggestions and feedback.

I ran the example and it initially crashed on my computer due to a back-dated graphics driver that does not support filled polygons. When I switched to DirectX mode, it worked for me.

It will be interesting to hear your comments about KML. In one sense, KML is sort-of like the OGC LOF draft specification.

I look forward to seeing more of your work. I'm hoping that one day Google Earth will be able to access WMS/WFS server via a user defined wizard.

Nice work, James. Your example works just fine for me (but I'm using a rather more recent build of the client than most).

As you have seen, KML is not GML. There are some strong similarites in places, but GML is purely descriptive (and is *huge*) whereas KML allows for such things as screenspace overlays and network links (and is *tight*).

We're working on the schemata files, and we will publish them ASAP. That should make life a little easier for you.

GML is indeed huge, but you can use a tiny subset of it and remain compatable. The one glitch that caused me the most grief is the coordinates having to have three values (not because they are hard, but because I had pass a 'generateDummyZ' flag into the core of the GeoTools GML engine.)

The addition of a gml namespace and a couple more tags and KML would contain a valid subset of GML making a lot of people lives easier for very little extra effort.

James

OK, for the interested I have attached the Styled Layer Descriptor document that controls how the map is rendered. Normaly this is used to generate an image such as a PNG or GIF but in this case it is used to generate stylized vectors in KML.

The document is made up of styling rules that look like this:
<Rule>
<ogc:Filter xmlns:gml="http://www.opengis.net/gml">
<ogc:PropertyIsLessThan>
<ogc:PropertyName>PERSONS</ogc:PropertyName>
<ogc:Literal>2000000</ogc:Literal>
</ogc:PropertyIsLessThan>
</ogc:Filter>
<PolygonSymbolizer>
<Fill><CssParameter name="fill">#fff7bc</CssParameter></Fill>
</PolygonSymbolizer>
</Rule>

i.e. if POPULATION < 2000000 shade fff7bc

(SLD 1.1 in draft includes support for classification functions which will make the SLD shorter, but functionaly equivelent)

I've not implemented it the KML bindings yet but SLD also allows for control over a large range of visual variables including line width, dash pattern, fill pattern, opacity, line caps, marker size, color and rotation. We do all of these for image generation, we will have to see how far KML lets us go.

So far I'm very excited by the possibilites.

James

James - looks good - I need the same done for all the country shape files. I have attached the gml - can you do the same conversion to gml ? Or is there a 'simple' conversion method ?

I too could only get it to work in DirectX mode. Other data has worked fine.

This is potentially an excellent tool for us GIS folks. When might this be released in the standard GeoServer build?

It's interesting how Google Earth is so much more GIS-savvy than Google Maps (who stuck their foot in their mouth at the Where 2.0 conference by saying they had never heard of OGC).

GlobalTrotter2,

Your data in GML for Australia is a little messed up. I was able to convert all the others; however, Australia is missing half of its coordinates. Can you post the GML for just Australia? Once I get Australia done correctly, I will post the whole thing.