Google Earth touring via KML

While I’m writing up old hacks, here’s one that I really enjoyed, even if it was a bit clunky. A couple of years ago Mikel Maron implemented (on my urging in #geo IRC :) a PHP-based Google Earth touring service, which interconnects a “tour guide” user with “tourists”.

This site facilitates collaborative, realtime exploration of Google Earth. As the “tour guide” navigates, “tourists” will automatically follow along.

When the tour guide’s Google Earth installation is at rest, a specially installed KML network link sends the server an HTTP request, showing the coordinates of the visible area of the globe. This same service is periodically polled (every second) by “tourists” whose Google Earth will dutifully fly to the appropriate spot.

The system seems to be offline currently, but was quite evocative to use, even if tricky. You never quite knew what the other party could actually see, since the picture can load quite slowly when moving around a lot. And the implementation didn’t do anything about angle of view (although this became possible in later versions of KML). I had experimental tours of Dublin guided by Ina (Skyping at same time), and of various places in Iran by Hamed Saber.

I expect in due course (if not already, I don’t track these things) Google Earth and similar products (Worldwind, or the Microsoft thingy) will offer social map browsing, it’s such a nice feature, though it really needs an audio channel open at the same time. Last week I tried to do the same without such a link, my mum talking me thru finding a small village in France. Much harder! “Take the road north out of Chabanais … past a small farm, past the swimming pool…”.

Here is Mikel’s “how it works” writeup:

The web interface generates KML files, which are loaded into Google Earth and create Network Links. The tour guide has a “View Based Refresh” Network Link, which sends the bounding box of the current view to the specified URL whenever the camera stops. That position is stored. Tourists receive a “Time Based Refresh” Network Link, which requests every 10 seconds and receives the last stored position of the guide.

Right now only location and altitude are transmitted. A future release of Google Earth may enable tilt and rotation. Integrated chat would be nice as well.

The fact that they’ve hidden a full flight simulator within Google Earth might make this worth revisiting. And of course there is infinite fun to be had from playing with photos etc on the globe, although my last attempts in that direction (preparing for 3 months in Buenos Aires by studying geo-tagged photos instead of Spanish) tailed off. Everyone was putting pics on maps, I got a bit bored, even though it’s still a worthwhile area with much still to be done.

Some ideas are not meant to be combined though: who really needs a collaborative realtime photo-navigator implemented with Google Earth flight simulator? :)

Open Source Flash Development and WorldKit

Handy article, “Towards Open Source Flash Development” by Carlos Rovira.

Background to looking at this is some great news: Mikel Maron is open-sourcing the WorldKit system, a lightweight Flash/SWF-based Web mapping application. So I’m interested to find some open source tools that would allow me to rebuild it from source.

I also wonder whether SVG hackers might be interested to port some of it to SVG/Javascript. WorldKit supports geo/rss location tagging, so I’m also curious about what it’d take to get full RDF support in there. Has anybody made an RDF parser for SWF/Flash yet?