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Interactive Spiders and Charts

December 24th, 2007 Leave a comment Go to comments

GPS Animation and Charts, Google EarthA couple of updates to my recent Google Earth GPS-satellite visibility animation:

Firstly, you can now change the viewing location to anywhere on Earth.  To do this, right click on the Location folder (with the blue dot) in the side panel and select Refresh.  The animation will then centre on the current view.

Secondly, the visualization displays a Screen Overlayed bar chart by hooking up to the new, and very slick  Google charts API.   The chart shows the duration, in hours, specific numbers of satellites are visible. The idea being to demonstrate how the distribution profile changes with location.

As a secondary (secondary) option you can view a 24 frame animated bar chart.  Where I cumulatively add the current hour’s stats, shown in red, to all the previous hours’ , shown in green.  A bit OTT, but interesting to see how rapidly the API dynamically generates the images on demand, and GE caches them.
Edit (2007-12-26): removed this option temporarily – see comments.

Download the file here:

GPS Animation ~200kB

There’s a useful tutorial on how to create and embed charts in KML balloons on the official Google Maps Blog.   Only difference I found in adapting it for KML Screen Overlays (or Icons, Ground Overlays and PhotoOverlays for that matter) is I needed to use &  instead of & in the URLs.

  1. December 25th, 2007 at 14:01 | #1

    Merry Xmas James!

    I just tried the KMZ file and ran into a problem with the chart. I’m thinking one posibilitiy is that you ran over the limit for the number of chart queries/day (which some people were saying was kind of low)?

  2. James
    December 26th, 2007 at 12:00 | #2

    Happy Christmas Frank!

    Hmm, you could be right. Seems fine now, but I didn’t check it yesterday.

    My server logs show the relocate script was called a couple of thousand times (more than I expected) . With up to 25 charts each time, I guess that might have pushed it over the API limit.

    Anyhow, I’ll remove the chart animation for the time being.

  3. December 27th, 2007 at 17:15 | #3

    Hello James,

    could you add an option to get the satelites some height? I’d like to see your excellent work from a valley of the Alps 🙂

    Thanks a lot.

  4. James
    December 28th, 2007 at 00:06 | #4

    Try this (a hack 😉 ):

    – Right click on the ‘Location’ folder. Select ‘Properties’
    – Change the link to:
    – Click OK, then Refresh the Location folder as normal.

    It just makes the sightlines point accurately upwards – doesn’t move the satellites or orbitals. Looks a bit strange, but it is based on realistic satellite heights.

  5. January 27th, 2008 at 12:17 | #5

    Thank you, James, very nice !

    In my surroundings there _is_ a difference between theoretical and real visibility (see screenshot: http://photos.franksteidl.ch/v/28215)
    I had a look on your lines… you set the endpoint in 22km height. How about the sattelites? I tried this and was impressed of the distance… zoomed out (got several times lost in space with my spacenavigator) and started the animation. Now every line got its sattelite at the end. While trying to raise the Groundoverlays I got lost in the gap between the overlays. I guess, the size needs to be multiplied with a factor and the altitude…
    On the way back in into my valley I liked to set the lines and sattelites to an altitude of 3km to get an better viewable imagination of GPS support in Europe. (see screenshot: http://photos.franksteidl.ch/v/28218)
    So my question: Would you mind to allow a &height= param to your script? I’d like the sattelites, the line endpoints and (if possible) the orbit overlays at this height…

    James, this is excellent work, thank you very much. Now I understand GPS a bit more with this 3d demonstration.
    Next thing could be to draw a cone shaped polygon and the action radius on the surface, with transparency to see the overlapping areas of several sattelites. 🙂
    (see screenshot: http://photos.franksteidl.ch/v/28224)

    Keep on coding, James.


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