Technical Ramblings

OpenLayers now has its own blog.

Thank the creation of Planet OSGeo for the final inspiration to actually put it together.

I finally got fed up with Planet GeoSpatial this weekend. Too much Google, too many formatting mess ups, and in general, too much crap. Although I appreciate that those who are working in the GeoSpatial space have a large interest in ESRI, Google Earth and Maps, and the general ‘state of the industry’, my target interests are much smaller. I just want to know about what’s going on in the world which affects Open Source GeoSpatial software: I wanted what is essentially “Planet OSGeo”, rather than “Planet Geo”.

(Note that this is a commentary mostly on my specific interests, rather than on Planet GeoSpatial, which James Fee has done a wonderful job on maintaining for the wider target audience he has.)

To that end, and with Sean Gillies’ excellent recommendation of Venus (omg, a version of Planet that *works*?), I’ve set up Planet OSGeo, a collection of Open Source GIS blogs.

Of note, I’ve not included several topics here, even though they are at least tangentially related to Open Source Geo:

• GeoRSS. There are a half dozen people who are regularly blogging about GeoRSS — not least, the GeoRSS blog. However, GeoRSS is not in and of itself “software”, which is my target interest, and I think the primary field in which OSGeo has thus far expressed an interest.
• OpenStreetMap. Although collection of Open Geodata is within the realm of OSGeo, at the moment I’m targeting software, and most of OSM’s blogging is not about software development.

(I’m happy to take feedback on my choices — or suggestions for more blogs!)

Notably lacking in this Planet:

• Blog for OpenLayers. Thus far, I’ve not set up a seperate infrastructure for OpenLayers blogging, sticking instead to the MetaCarta Labs blog. I think the time has come to grow out of that, and move into some OpenLayers infrastructure for blogging.
• Blog for GDAL. The library at the base of much of the Geo software on the web doesn’t have an RSS feed — for either announcements or general project discussion. Some of this is probably representative of the stability of the project: certainly after as many years as GDAL has been around, there’s limited content in terms of “Rapid Development” that many other tools like web mapping clients are still undergoing. Still, an announcements log with an RSS feed would be cool.
• MapServer. MapServer doesn’t seem to have a blog or RSS feed out of its website that provides interesting announcement-style updates, which would be good to see.

I think the things I see as ‘missing’ clearly demonstrate my bias in development and usage of tools — so I’m sure more people can point out what else I’m missing.

Looking forward to any feedback you might have.

Made a ‘screencast’ (at least, I think that’s the right buzzword) of OpenLayers + QGIS today:

Mapping Your Data: Using QGIS, OpenLayers, and MapServer to serve open data

Tried uploading it to YouTube: the resolution was shrunk to the point of being unsable. Tried uploading to Google Video: despite the upload completing 11 hours ago, the upload is still ‘processing’. So I went through with ffmpeg and converted it to Flash myself, and set up the environment for playing it on openlayers.org.

To create the video itself, I used:

• Snapz Pro X (Shareware: $60)
• ffmpegx (Shareware: $15)
• Flash Video Player (Free for Non-commercial use: $15 commercial license)

In the video, I used TextMate (Shareware), QGIS (Open Source + Free), Firefox, and OpenLayers.

(There is no audio in the presentation, because I felt like my voice would be a distraction. I suppose next time I should put some fancy soundtrack in place.)

At BarCampBoston today, I got to talking to the OLPC folks. I was demoing our new vector editing support in OpenLayers, and talking to them about it. They wanted to see if it would run on their laptop, and we got an error that SVG wasn’t supported in their browser. After a bit of effort after getting home tonight, I was able to find out how to check for SVG 1.0 instead of 1.1 — after modifying the OpenLayers code to do a 1.0 check instead of a 1.1 check, I got a confirmation that vector display works on the One Laptop Per Child laptop! Woot. Filed a ticket with a patch for OpenLayers: 540, just need to get someone to review it and check it in.
So, the next step is to help the OLPC folks get up and running with OpenLayers. 🙂

So, last week was an OpenLayers hack week. One of the things that we did was make adding support for new vector formats trivial. Instead of modifying several parts of the code, you only need to create two functions: a ‘read’, which takes a set of data — XML, strings, Javascript object, what have you — and returns a list of OpenLayers.Feature.Vector objects, and a ‘write’ which does the reverse — takes a list of objects and returns a string or object or XML.

To prove this, I set out to write some additional vector format support last night. I decided to add one read, and one write.

• Read: KML. I added support for KML point display in about 20 minutes, including the time to find data and write a demo HTML page loading some example data. Adding LineString support was another 15 minutes.
• Write: GeoRSS. Support for writing georss:simple points, lines, and polygons was simple… once I found data. I asked for a live example, and was unfortunately unable to find any valid line data outside the GeoRSS website, so I just generated something that was as close as I could come to the examples. I’m lazy, so the export is just RSS 2, and I’m sure that someone will come along and criticize it, but that’s one of the benefits of Open Source: Anyone can offer up a patch. Time from when I created the file stub to when I committed the code was 27 minutes, again, including a demo.

Altogether, the Format support in the new OpenLayers is pretty cool. Because of the way it’s built, I can even do something that is pretty damn ridiculous: Import KML, and export GeoRSS (or GML), all from the browser. Certainly, this is an incredibly crazy thing to do, but OpenLayers is a pretty crazy project.

I’m convinced that there’s nothing in the code that would make it difficult for someone who’s comfortable working with Javascript to write support for any simple-to-parse format. Now, to get the code back to trunk and get the patches rolling in.