Archive for the Open Source Category
Just a quick note asking you to VOTE for the solutions you think are best in the current GeoWorld Geospatial Leadership Awards.
Some interesting entries have been nominated. In particular, FDO and Fusion (both open source applications) are competing alongside other prominent applications in the Innovator Award category.
Full disclosure: My work on earth.nanaimo.ca (built with MapGuide Open Source technology) is nominated for the Public Enterprise category. Please only vote for it if you think it’s the most deserving solution in this category.
-J
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James’ recent post about the GIS Interchange File reminded me that I’ve been meaning to discuss some recent activity on the SQLite front in both FDO and OGR.
Traian Stanev recently proposed the creation of an SQLite provider for FDO. He was quickly arm-wrestled into supporting something close to OGC’s Simple Features for SQL specification, and working with Frank Warmerdam hammered out a GIS spec for SQLite that would work for both OGR and FDO. The beauty is that it’s a single file and can be read by any of the existing SQLite tools.
Traian completed initial development of the SQLite provider a couple weeks ago and Frank expanded OGR’s SQLite support to understand this common specification (this work is in the GDAL/OGR trunk for inclusion in the 1.6 release). These implementations have different strengths. The FDO provider was written to be blazing fast, features an in-memory spatial index, and writes to the FDO binary format. The OGR driver was written for maximum portability and allows writing WKT and WKB. Both implementations will read all three geometry formats and understand the dimension and projection information stored in the OGC-derived metadata tables.
You can download a totally unofficial build of the FDO provider from my website if you want to try it out with MapGuide 2.0 or maybe even Autodesk Map 3D 2009. I have successfully tested it in MapGuide with WKT, WKB, and FGF data. Adding this provider to MapGuide is easy:
- Drop the three files in the zipfile into your Server/bin/fdo directory
- Edit your main providers.xml file to include the SQLite provider using the included XML snippet
- Restart MapGuide
You will need some data. Testing can be done with SQLite files from the OGR sample data directory, but you will eventually want to use your own. It’s fairly simple to convert SDF and SHP. Open up a command window in your Server/bin/fdo directory and type something like:
SQLiteConverter.exe c:\src.sdf c:\dest.db
When creating a new data connection to this file, the provider only takes one configuration parameter: the full path to the file. If you run into any bugs, please post them on the FDO Trac instance.
OGR users that are tracking the trunk build can also try this out. With some amazement, I recently found that the enhancements to this driver had already been documented… obviously OGR places a premium on timely docs. ogr2ogr allows you to do a similar import operation, probably something like (untested):
ogr2ogr -f "SQLite" -dsco FORMAT=WKB dest.db src.shp
You can use additional ogr2ogr arguments to ensure that destination spatial reference and geometry type are written to the metadata tables.
Interestingly enough, a common SQLite GIS specification has been kicked around for quite some time. Last year it was discussed on the OSGeo Discuss mailing list, and more recently further discussion was held on the PostGIS mailing list and a wiki page was set up to collaborate on this idea. Obviously, there is considerable interest within the community. My personal hope is that this specification helps the idea of SQLite as a GIS data store take off.
One area where it could be improved is some kind of integration with Alessandro Furieri’s SpatiaLite extension for SQLite that allows common RDBMS GIS functionality in a native SQLite interface. Unfortunately, neither Frank nor Traian had the cycles to integrate this extension’s data format into the specification or the code at this point. Maybe we’ll get lucky and Alessandro will decide to somehow support this spec, but if not I hope there will be some convergence in the long run.
I know that there was more that I wanted to say, but it’s getting late and I don’t even have time to cut the extra gunk out of this post. Happy SQLiting!
-J
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The recent FDO 3.3.0 release comes with beta support for MS SQL Server Spatial. Adding this provider to MapGuide 2.0.0 on Windows is as simple as copying a few DLLs and updating the XML provider registry.
You’ll have to take my word for it, but all of the layers here are coming from SQL Server 2008:
There are a couple small gotchas that I ran into.
If your data contains geometry inconsistencies (basically anything that doesn’t match OGC geometry specs) then the February CTP of SQL Server 2008 will cause spatial queries to fail. Apparently Microsoft may be relaxing this validity requirement in future CTPs, but for now if you have “invalid” geometry, you will have to modify it.
You can find these problems with the GEOM.STIsValid() function and fix them manually, or you can get SQL Server to “fix” the problems with a statement like this:
update dbo.YOURTABLE set GEOM = GEOM.MakeValid();
The second issue was a defect in the provider that causes spatial filters to fail if you set the SRID (spatial reference) on your data. This is because with SQL Server 2008 the SRID of the filter geometry has to match that of the database, and the provider is not setting a SRID for the filter geometry.
For now, you can work around this by removing the SRID from your features with a statement like this:
update dbo.NAN_PARCELS set GEOM.STSrid = 0;
Apart from these two minor glitches, the provider is looking good so far. I’m hoping to get a chance to test it further with later releases of SQL Server 2008 and of the provider to see how well it performs.
If you get a chance to try this out and run into any further problems, please enter a good description of the problem into the FDO Trac issue tracker. The more you test now, the more likely it will work in your production environment later!
-J
P.S. Thanks to Orest at Autodesk for helping me work through these initial issues!
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If you’re interested in seeing what the recently released MapGuide Open Source 2.0.0 with DM Solutions Fusion (which in turn uses OpenLayers) looks like, you’re in luck!
We’ve put together an experimental / beta server for us to demonstrate and test new features for MapGuide. For now, it’s showing MGOS 2.0.0 Release, with some minor tweaks to the templates to use 8bit PNGs. Have a look here:
http://mapguidebeta.osgeo.org/
-J
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Fusion is incredibly flexible and cool technology for building web mapping applications. It is also very new technology with limited documentation, leaving more than a few people wondering how to figure it out.
Not to worry, help is on the way! 
With the MapGuide Open Source 2.0 Beta2 release, a bit of documentation for Fusion was quietly placed in the MapGuide section of the OSGeo download server.
These docs are still a bit “beta” (ie. incomplete), but there is some good information in there for anyone looking to get their feet wet with Fusion. I would suggest ignoring the “Installing and Configuring” doc. Start with “Introduction” (briefly), go on to “Generic Web Mapping Application Components”, then “Widget Concepts”, and finally “Create A Basic Web Mapping Application”.
Apart from the documentation, there is also a new template called “learn” included in the Beta2 installer. Look familiar?
That’s right, this looks a LOT like the existing “AJAX” viewer. Although it isn’t as fancy as the fusion templates that I posted about previously, it does have a lot of functionality. Fortunately, it is absolutely riddled with comments, and is a lot easier to reverse-engineer. It is a good starting point for beginning to understand some of the more involved Jx layout capabilities, advanced widgets, etc. You can find it in the MapGuide install directory, under
WebServerExtensions/www/fusion/templates/mapguide/learn/.
If you are looking for something more bite-sized to get started with, you might also find this small code sample useful:
http://trac.osgeo.org/mapguide/wiki/CodeSamples/Fusion/SuperSimple
This gives you an _extremely_ basic application that uses a few lines of straight HTML/CSS/XML and no JavaScript other than what Fusion loads itself. I obviously didn’t take too much time to make it look pretty:
I have high hopes that the Fusion documentation will be considerably more complete before MapGuide Open Source 2.0 is released, but now early adopters have something to play with.
If you haven’t downloaded the latest beta, please help us to make it better by trying it out and reporting any problems.
-J
