I'm using a KML file which I have loaded in to Google Earth. I am looking at some islands, and see items such as the following island:

enter image description here

Note the blue region is the polygon describing the area provided, and the image in the background. Sometimes I see similar shapes, but they are off a bit, such as below:

enter image description here

Bottom line is, I'm trying to get as accurate of a map of some of these island nations that I can. Is it fare to use the image that comes from Google Earth to attempt to make a better representation of such islands, or is there enough inaccuracy in the creation of Google Earth islands that it is not worth making any changes?

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    Where did the KML data come from? It's possible it was projected with an incorrect transformation at some point, causing a shift. More likely though is it was simply intended to be used at much smaller scales (more "zoomed out") and the inaccuracy is not because of Google's imagery, but how your data was produced. – blah238 Nov 2 '13 at 1:37
  • @blah238: It seems to me that they didn't care about the islands as much, but in general, the data is poor. I'm just looking at stuff like this and thinking that it might be improvable. The data came from Geo Commons, geocommons.com/overlays/101187 – PearsonArtPhoto Nov 2 '13 at 2:10
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    In my experience, islands are less accurate on Google Earth than mainlands. I have seen an island in Australia that was split vertically between two different images. The difference between the two was about 50-100 metres apart. I think they've since updated the imagery there and it looks better now. But, generally, I wouldn't trust the imagery for anything important. – Fezter Nov 2 '13 at 3:24
  • If you trust inn Google Earth, better not look at this: thedailywtf.com/Articles/Google-Earth%28quake%29.aspx and techeblog.com/index.php/tech-gadget/… – AndreJ Nov 2 '13 at 6:31
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    @AndreJoost - I get your point, but funnily enough that image from GEarth gives me more confidence in the geographic accuracy of the product! The digital elevation model doesn't take into account the bridges, but the highway below (lower elevation) seems perfectly aligned and the right sort of depth. Compared to the ± 1km accuracy I've seen elsewhere, anyway. – Simbamangu Nov 2 '13 at 12:13

The answer (of course) is "it depends". Google earth isn't a single set of data - its a sequence of images, and some of them are more accurate (better aligned) than others. Things change over time too (tides, storm erosion are all factors at the sort of island scale you're considering)

Note: In terms of deriving product - you are probably not compliant with the Terms of Use for google earth if you're copying it.

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