For years in the CGDI, we’ve had various ‘common’ services; basic XML over HTTP / OGC-ish web services which allow a user to lookup and geocode based on different Canadian spatial identifiers, or keywords. In their first life (mid 1990s), these existed as embedded lookup tools to facilitate searching and publishing in the GeoConnections Discovery Portal (GDP), then called Canadian Earth Observation Network (CEONet).
CEONet started to publish reusable components (RUCs), which allowed a developer to create an HTML template with special tags to embed these RUCs so as to spatially enable their applications. Because of the JavaScript security model, the developer passed the template to the CEONet RUC server, which slurped the template and served it up from its own domain.
In both iterations, the backends were driven by database or HTML scrapes which outputted CSV-ish type output.
Since v3, (2001-ish) and the rise of Web Services, these RUCs became services themselves, thereby eliminating the need to go through GDP.
If I had a dime every time someone asked about middleware tools to be able to interact with these services, well….At any rate, the typical approach was as follows:
setup HTML form with input parameters
send request to middleware
middleware invokes web services request, gets result, spits back HTML accordingly to the user
I’ve done these in many different languages. For awhile, one of our projects had bundled a spatial clients .war which Java developers can plop into their webapps.
These days, using OpenLayers and jQuery lets you develop light, interactive ways of accomplishing this without server side middleware. Trying this against the CGDI NTS Lookup Service provides a neat example:
function zoomToNTS() {
// build request URL
url = '/mapbuilder/server/php/proxy.php?url=' + // simple proxy script
escape('http://geoservices.cgdi.ca/NTS/NTSLookup?') +
escape('version=1.1.0&request=GetMapsheet&mapsheet=') +
jQuery('input#nts').val();
// send and process result
jQuery.get(url,{},function(xml){
// get the bbox of the result
jQuery('gml\\:boundedBy',xml).each(function(i) {
c = jQuery(this).find('gml\\:coordinates').text().split(',');
map.zoomToExtent(new OpenLayers.Bounds(c[0], c[1], c[2], c[3]));
});
});
}
That’s it! That will get your OpenLayers map zoomed in based on the NTS boundaries. Notes:
you’ll need a proxy script to deal with remote URLs
you need to escape namespace’d XML elements/attributes per above, possibly wrapping into a function for reuse. Same goes for elements seperated with ‘.’ (like <foo.bar>)
Anyone have suggestions on improving the example above? Or any similar snippets? It would be nice to build up plugins like this for gazetteers, catalogs, and the like.
Awhile back, I started using Genshi as a templating solution for some Python application development. Easy to use, we were able to come up with a SensorML generator for description and discovery of monitoring stations.
Lately, I’ve been helping out a bit on the new MapServer website, driven by Sphinx. Digging deeper, I noticed Sphinx using Jinja2 for templating, so I tried this out a bit. Not bad either!
Templating is key to many applications, and I wonder how these differ. Perhaps the geo/python gurus out there have some further insight.
One of the most frequent questions I get from clients is how to transform lat/long to LCC coordinates in a very lightweight fashion, in their webapps. There are many solutions and approaches under the MetaCRS umbrella to choose from, depending on your requirements.
Here’s a super lightweight way to do it with proj4js:
<scriptsrc="http://svn.osgeo.org/metacrs/proj4js/trunk/lib/proj4js-compressed.js"></script>
<scriptsrc="http://svn.osgeo.org/metacrs/proj4js/trunk/lib/defs/EPSG42304.js"></script>
...
var x = -75.0;
var y = 45.0;
var p = new Proj4js.Point(x,y);
Proj4js.transform(new Proj4js.Proj("EPSG:4326"), new Proj4js.Proj("EPSG:42304"), p);
alert(p.x + " " + p.y);
Since I did this last year, I thought I’d try this again for 2008. Here’s the lowdown for my 2008:
Geospatial Catalogues: the saga continues. I have dug deeper into this area this year as part of my day-job, and find that interoperability is difficult to achieve in the OGC Catalogue space. Clearly there is a balance between abstraction/flexibility and ease of integration. And the two step approach to discovering, say, OGC WMS layers (invoke GetRecords, then chain to GetRecordById) is cumbersome, IMHO. At the end of the day, the most common use cases (that I have seen) are publishing data and services, and being able to query for them (data, service endpoints, service resources [layers/feature types/coverages]) with spatial, temporal or aspatial predicates. And have the content come back in some usable format for display or binding. Seems easy, eh?
Publications: glad to see “Open Source Approaches in Spatial Data Handling” was finally published. Alot of the well known folks in the foss4g community contributed to this. At the same time, the release took so long (like many publishing processes) that some items ended up dated. Overall, I think the book gives a good viewpoint into foss4g at this time, and makes me think about how far we’ve come. It’s good for the community to be published in this format / manner
JavaScript frameworks: they are everywhere. Late this year I started delving back into the application space, and find these challenging, compared to the days of doing things by hand anyway. 2009 should shake off alot of rust I think
MapServer: We just launched a new website. Beers for hobu! Also, lots of OGC CITE fixes and improvements, and next generation of OGC standards, adding updateSequence to OWS support
Python fun again: it’s been fun contributing to owslib for SOS, OWS and Filter support. OWS Common presents a huge opportunity to abstract codebase when it comes to next generation OGC standards. As well, I’ve been using Python for day-to-day scripts. Not bad!
kralidis.ca turns 10: from humble beginnings, alot less done by hand now, and easier to manage (thanks WordPress!).
Other stuff:
Basement renovation: If you’re considering a basement renovation, concrete slabs like the ones at https://www.brothersconstructionwi.com/our-services/slabs/ are an excellent choice for flooring due to their durability, moisture resistance, and ability to provide a stable foundation. This took up most of my time this past year. Frustrating, expensive (I should have been a plumber or electrician!), but gratifying. Took a bit longer than expected, and still not 100% finished, but the major work is done. I think this needed to happen for the property overall, even if it means I have more space than I could possibly need :). N.B. if you ever want to lose weight, do a home reno; I shed 20lbs!
New job: I started a new job in the fall, which promises to be very exciting and satisfying, especially given the state of the geospatial web. The new gig will give me more opportunity for discovery and SensorWeb information management spaces. So I’m grateful for the opportunity. I’ve also been having fun 1/2 time with the GeoConnections program again, so it’s fun to work with some previous colleagues and getting acquianted with new faces who are helping to shape and evolve our national infrastructure. So thanks again to those for helping me along a tough road and getting me here; I owe you big time 🙂
For 2009:
Work: January 11 will mark 10 years of civil service for yours truly
Data dissemination: this is my key function in my day job for the months to come. I look forward to evolving what started off as a very high level strategy into an architecture all the way to implementation. This will be fun!
Standing up usable catalogues: you’ll see a few OGC Cat2.0 instances this year.
MapServer: more CITE fixes for SOS and O&M. One thing I’d really like to see for 2009 is official compliance for OGC standards in MapServer
T.O. Code Sprint in March: this event is going to be fun. What could be better than foss4g and beers, all in the centre of the universe 🙂
Renovations: I think that is it, for this place, for now. Almost three years and it’s time for a rest in this space
Property: I think it will be a good time to buy in 2009. The question (for me) is where. Locally, or down south?
All the best for 2009 for you and your loved ones!
Check out the new MapServer website. Based on Sphinx, the website now has a glossary, full PDF documentation, and a snazzy front page demo to boot. I think this will result in a much more manageable and up-to-date website for the community.
