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Géoportail tiles in Google Earth, anyone?

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Brian Flood’s post on Friday about superimposing Google Maps tiles onto ArcMap reminded me of the early hacks by Dan Catt and Bernhard Sterzbach that superimposed those tiles onto Google Earth. (BTW, Bernhard’s hack still works!). This in turn led me to wonder whether it is possible to write a network link that overlays Géoportail tiles onto Google Earth. I think it should be very possible, technically. I’m not a programmer, though, so it’s beyond me. Perhaps somebody else…?

IGN might not like it, but that would just drive home the point that data and delivery are two very different pursuits, and that trying to tie specific data to a specific delivery mechanism is just silly in this age of open standards.

I think Géoportail’s tiles on top of Google Earth would give me and every French citizen the best of both worlds, (literally, ha). It would even allow us to watch the Tour de France on top of IGN data. And who could be against that? :-)

Meanwhile, now that I’ve actually been in and tested Géoportail, I cannot say I’m impressed. I think it is very much a second-rate implementation of the 2D mapping genre:

  • Many of the overseas territories, such as French Guyana and St. Pierre & Miquelon, do not have any imagery whatsoever, just scans of maps or relief maps. As for French Polynesia, you can click on it, but then you get the message that there is no data at all available for it. So much for that much-vaunted consistency.
  • I spent an inordinate amount of time trying to zoom in on a farm in the French Pyrenees where I spent many summers growing up. The darn tile just refused to load. Often, it feels like you’re navigating a chess board instead of France.
  • In Firefox on a Mac, i regularly get told off for unresponsive scripts, followed by the announcement that Géoportail has encountered an unexpected error and needs to close. Remember, this is not beta.

(And lest anybody think I’m anti-French, I’ll be rooting for Zidane and his team in the finals.)

5 thoughts on “Géoportail tiles in Google Earth, anyone?”

  2. Zmarties, compare it to the Pages Jaunes. One reviewer I’ve read noted that the Pages Jaunes dataset, while nominally the same as IGN’s, manages not to distort the imagery. Is this something you can confirm? Perhaps the network link could reference the Pages Jaunes tiles.

  3. Interestingly, Google’s lawyers got unleashed on NASA full force when someone tried to do this exact same thing with Google’s tiles. :)

  4. Also, the reason for the distortion (in that runway picture, at least) is because of the orthorectification process. This is the process where they stitch together a bunch of still images of small areas into one big mosaic of the whole area where the picture seems to be taken from a point directly above every point in the image.

    You can’t just line the pictures up edge to edge because they overlap and are very distorted nearer the edges, so you essentially combine the least-distorted area in the center of each image to contribute to the mosaic. This results in small (but generally acceptable) amounts of distortion in the final image. Large objects with long, straight lines tend to highlite these distortions. Tall buildings can also look strange after this process.

    To reduce the amount of distortion you need to take more closely-spaced pictures during the flight.

  5. Hi Stefan,

    you can indeed overlay IGN Geoportail tiles on a 3D view. A plug-in has been developped. It is not on Google Earth though, but on the Google Earth like (was developped prior to GE) Open Source Software (NASA World Wind).

    For those who can speak French, you can get explanation there:

    http://www.premiumwanadoo.com/rochesaintsecret/geolocaliser.php3

    For English speaker, please rather have a look there :

    http://thepochisuperstarmegashow.com/2006/08/14/ign-geportail-in-3d-with-world-wind/

    Here you can get a screenshot of the view obtained in Drome Provencale (south Alps):

    http://www.premiumwanadoo.com/rochesaintsecret/temp/rocheaudeladerachas.jpg

    Note that you can access the code that retrieves the tiles since it is open source code… that’s great.

    Cheers from France,

    Superggm.

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