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could someone clear this up for me please. i remember reading an article not long ago on the web about the problems associated with buffering points on a globe due to the fact that a globe uses angles instead of cartesian coordinates on a plane. the implication was that the usual buffer visualization of concentric rings was totally false when using large areas...ie 500km+.

i just saw this graphic on a bbc site, and wanted to find out if this representation is correct or not.

http://www.bbc.co.uk/news/world-asia-22131316

scroll down for the graphic.

is this graphic accurate?

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  • oringal article was here.esri.com/news/arcuser/0111/geodesic.html
    – Robert Buckley
    Apr 13, 2013 at 10:41
  • It looks fine to me (assuming the distances are right). The equidistant projection is distorting areas, but the "is this country inside this distance" part looks fine. Perhaps you can explain your concern with it again?
    – BradHards
    Apr 13, 2013 at 11:13
  • my original concern lied with the fact that i couldnt assess whether it was correct or not
    – Robert Buckley
    Apr 13, 2013 at 13:10
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    The problem is nicely illustrated in the answer at gis.stackexchange.com/a/8031.
    – whuber
    Apr 13, 2013 at 14:44

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The graphic is accurate. The projection is azimuthal and centred on North Korea, so all the ranges are concentric circles. I checked it on Google Earth with this GE circle generator tool, and here is the result

Google Earth

Although not exactly the same projection, but you can see the range circles match. They would have encountered trouble with this specific projection if the range was greater than a quarter of earth's circumference, (But then I guess it would be the least of our problems, I mean, NK has a missile with 10,000Km range...) .

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    If you more carefully compare the radii in the graphic to the radii in your image, you will find the original graphic contains considerable distortion: it can be read only qualitatively, not quantitatively.
    – whuber
    Apr 13, 2013 at 14:46

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