My talk: The State of GeoCouch

I'm really happy how my talk went, I really enjoyed it. The were lots of people (although there was a talk from Frank Warmerdam at the same time) asking interesting questions at the end.

The talk is not only about GeoCouch but also gives you an overview of some of the features it leverages from Apache CouchDB. In the end you should have an overview why you might want to use GeoCouch for your next project.

You can get the slides right here.

• The slides (download optimized) as PDF (licensed under CC-BY-3.0-de).
• The slides with comments as HTML (licensed under CC-BY-3.0-de).
• The slides with audio. It’s the recording of the actual talk at the conference.

Other talks

I was happy to see that there was another talk about GeoCouch. Other talks I really enjoyed were:

• CartoSet, a new FOSS to create highly visual geo portals: So many true things were said, e.g. get the data from the customer first, before you start building anything.
• Introduction to OpenSource WebMapping: Beyond Google Maps: A very nice introduction off the full stack for web mapping. From the database, over the server to the client. It's for people that have no clue that they could have maps on their own infrastructure.
• Comparing GeoExt, MapQuery and Legato from a technical and collaborative point of view: A good comparison between GeoExt, MapQuery and Legato. I especially liked the “Bodo”-test.
• Beyond vectors: Adapting remote sensing research for environmental monitoring with open source hardware and software: Citizen mapping the BP oil spill with balloons and kites: Kite and balloon mapping is just awesome. It's kind of the OpenStreetMap for raster data.
• GeoGlobalDomination: The Musical: One of the highlights was the GeoGlobalDomination musical. Grab the video while it's hot.

And of course there were also great talks from in the plenary sessions from Paul Ramsey about Why do you do that? An exploration of open source business models and Schuyler Erle's so funny lightning talk about Pivoting to Monetize Mobile Hyperlocal Social Gamification by Going Viral

Code Sprint

At the code sprint I was working on MapQuery together with Steven Ottens and Justin Penka. Steven was working on TMS support, Justin on a 6 minutes tutorial and I on making manual adding of features possible.

The OpenLayers developers did the migration from Subversion to Git for their development. OpenLayers is now available on Github.

And luckily there was a fire alarm in between to take a group photograph.

Future of the FOSS4G

I really hope there won't be a yearly FOSS4G conference for the whole of the US. There should be regional events, as I think one big one would draw the attention away from the international conference. Why should you fly to Beijing for the FOSS4G 2012 if you can meet the majority of the developers in the US as well?

Final words

The FOSS4G was great. It was organized well and people were always out in the evenings. The only minor nitpick is that many people working remote had the city of their company in the name badge and not the one they live in. It seems that the original for you had to fill was confusing. So for next year it should perhaps say “Location where you live”. Hence I still don't believe that there were more Dutch than German people at the conference (Tik hem aan, ouwe! ;)

I had the chance to tell people a bit more about CouchDB and Couchapps,

One project I haven't heard that much before of was Degree. They build the whole stack of OGC services you could imagine. For me it was of interest that they have a blob storage in their upcoming 3.0 release. The data isn't flattened into SQL tables but stored as blobs. This sounds like good use for a CouchDB backend in the future.

I was working with Simon Pigot on a GeoNetwork re-implementation based on CouchDB using Couchapp. We got the basic stuff like putting an XML document into the database, editing it and returning the new document, as well as fulltext indexing with couchdb-lucene work. Next steps are improving the JSON to XML mapping and integrating spatial search based on GeoCouch.

The event was really enjoyable, thanks Couchio for sponsoring the trip, thanks Jeroen for organizing it, and thanks all other hackers that made it such a awesome event. Hope to see you next year!

Normally when you drag the map in OpenLayers it will stop dragging as soon as you hit the edge of the map viewport (the div that contains the map). Whenever you have a small map, but a huge window and a loooong way to drag, it can get quite annoying, as the maximum distance you can drag at once is the size of that viewport.

But yesterday it finally happend. A patch to fix it landed in trunk. A first rough cut was made at the OpenLayers code sprint at the FOSS4G. Andreas Hocevar reviewed the code and made a more unobtrusive version of it (thanks, again).

Try these two examples to see the difference. Click on the map an drag it a long way to the right and back to the left again (you might need to zoom it a bit to see the full effect):

• default behaviour
• documentDrag behaviour

As it is a new feature, it isn’t enabled by default (and only available on current SVN trunk, it will be available in OpenLayers 2.9). To enable it on your map, just use the following code to add the documentDrag parameter to the DragPan control (you obviously need a recent SVN checkout).

Update (2009-11-18): It got even easier with r9805:

// Use default controls but with documentDrag enabled.
var controls = [
    new OpenLayers.Control.Navigation({documentDrag: true}),
    new OpenLayers.Control.PanZoom(),
    new OpenLayers.Control.ArgParser(),
    new OpenLayers.Control.Attribution()]
map = new OpenLayers.Map('map', {controls: controls});

For a full working version have a look at the source of the documentDrag example. ]]> http://vmx.cx/cgi-bin/blog/index.cgi/drag-as-long-as-want%3A2009-11-11%3Aen%2COpenLayers%2CJavaScript%2Cgeo/feed/ http://vmx.cx/cgi-bin/blog/index.cgi/list-function-editing-in-futon%3A2009-07-19%3Aen%2CCouchDB%2CJavaScript http://vmx.cx/cgi-bin/blog/index.cgi/list-function-editing-in-futon%3A2009-07-19%3Aen%2CCouchDB%2CJavaScript#comments Sun, 19 Jul 2009 17:54:46 +0200 Volker Mische en CouchDB JavaScript http://vmx.cx/cgi-bin/blog/index.cgi/list-function-editing-in-futon%3A2009-07-19%3Aen%2CCouchDB%2CJavaScript/ Futon is the graphical administration interface for CouchDB. It’s nice and slick for browsing and editing views, but there is one feature missing: you can’t edit _list functions in similar fashion. You need to edit them as JSON strings.

As I wanted to play a bit with _list, I’ve created a branch which implements such an interface. Its usage should be quite self-explanatory. Just select a _view, from there you can switch to the "List" tab to create or edit a _list function.

You can get my futon-list branch at GitHub. Instead of using git, you can also download the share/wwww directory (click on the download button within the ‘share/www’ directory) and unpack it over your current source.

In case you wonder why your _list function doesn’t work, the API has changed for CouchDB 0.10.

Screenshot of the _list interface in Futon

You can either add a _list function as described in the documentation or use my futon-list branch which includes an interface for easier _list function creation/editing.

Your data

The _list function needs to match your data, thus I expect documents with a field named location which contains an array with the coordinates. Here’s a simple example document:

{
   "_id": "00001aef7b72e90b991975ef2a7e1fa7",
   "_rev": "1-4063357886",
   "name": "Augsburg",
   "location": [
       10.898333,
       48.371667
   ],
   "some extra data": "Zirbelnuss"
}

The _list function

We aim at creating a _list function that returns the same response as a normal _view would return, but filtered with a bounding box. Let’s start with a _list function which returns the same results as plain _view (no bounding box filtering, yet). The whitespaces of the output differ slightly.

function(head, req) {
    var row, sep = '\n';

    // Send the same Content-Type as CouchDB would
    if (req.headers.Accept.indexOf('application/json')!=-1)
      start({"headers":{"Content-Type" : "application/json"}});
    else
      start({"headers":{"Content-Type" : "text/plain"}});

    send('{"total_rows":' + head.total_rows +
         ',"offset":'+head.offset+',"rows":[');
    while (row = getRow()) {
        send(sep + toJSON(row));
        sep = ',\n';
    }
    return "\n]}";
};

The _list API allows to you add any arbitrary query string to the URL. In our case that will be bbox=west,south,east,north (adapted from the OpenSearch Geo Extension). Parsing the bounding box is really easy. The query parameters of the request are stored in the property req.query as key/value pairs. Get the bounding box, split it into separate values and compare it with the values of every row.

var row, location, bbox = req.query.bbox.split(',');
while (row = getRow()) {
    location = row.value.location;
    if (location[0]>bbox[0] && location[0]<bbox[2] &&
            location[1]>bbox[1] && location[1]<bbox[3]) {
        send(sep + toJSON(row));
        sep = ',\n';
    }
}

And finally we make sure that no error message is thrown when the bbox query parameter is omitted. Here’s the final result:

function(head, req) {
    var row, bbox, location, sep = '\n';

    // Send the same Content-Type as CouchDB would
    if (req.headers.Accept.indexOf('application/json')!=-1)
      start({"headers":{"Content-Type" : "application/json"}});
    else
      start({"headers":{"Content-Type" : "text/plain"}});

    if (req.query.bbox)
        bbox = req.query.bbox.split(',');

    send('{"total_rows":' + head.total_rows +
         ',"offset":'+head.offset+',"rows":[');
    while (row = getRow()) {
        location = row.value.location;
        if (!bbox || (location[0]>bbox[0] && location[0]<bbox[2] &&
                      location[1]>bbox[1] && location[1]<bbox[3])) {
            send(sep + toJSON(row));
            sep = ',\n';
        }
    }
    return "\n]}";
};

An example how to access your _list function would be: http://localhost:5984/geodata/_design/designdoc/_list/bbox/viewname?bbox=10,0,120,90&limit=10000

Now you should be able to filter any of your point clouds with a bounding box. The performance should be alright for a reasonable number of points. A usual use-case would something like displaying a few points on a map, where you don’t want to see zillions of them anyway.

Stay tuned for a follow-up posting about displaying points with OpenLayers.