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I've been thinking about this last a few days. In internet i've searched about the projection systems of mobile mapping systems like google maps, bing, esri and others. I've found that they are using a projection called EPSG 3857. Also Nutiteq using this system. I'm still searching the parameters of this projection. But I've found only a very short description of EPSG 3857 in wiki page. I'm drawing a polygon on Nutiteq and calculating the area but I need this areas technical background.

Maybe someone knows the answer.

Thanks in advance...

Capan
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1 Answers1

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If you take EPSG 3857 coordinates (which are technically meters) and apply some simple area (or also distance) calculation algorithm, then you will get wrong result. To be be exact, it is more or less correct in equator, but more and more wrong towards either of the poles.

You must convert coordinates to latitude and longitude (also known as WGS84, or geographical coordinates, or EPSG:4326), and then use proper spherical calculation. Here seems to be good example for Android.

Community
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JaakL
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  • Very well now I understand it better. I have another question I've checked the example codes too but couldn't see any limitation about area. As far as I know Earth's spherical shape can be underestimated for the areas under 200 km2 . If I want to calculate this kind of little areas should I have to use proper spherical calculation anyway ?? – Capan Nov 02 '14 at 14:39
  • EPSG:3857 projection works for distances and areas only near equator, in middle latitudes it would be about 2 times wrong, regardless or area size. The problem is that mercator meter is itself distorted (in longitude direction), the problem is not about local curvature of earth. With some other projection (e.g. local one) 200km2 rule may work. – JaakL Nov 23 '14 at 16:22