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I have a simple question. I have calculated the area of the polygons in my shapefile, but the number seems confusing for me. I need the area to be shown in km2 but instead I get numbers like:0.004008 What are the units of this number?

When I used the "measure area" icon, that is, when I measured the same polygon manually the size of the polygon shows me: 50.342km2

See, the two numbers are completely different. How is that??

Thanks for any help!!

user29156
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1 Answers1

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QGIS reports information according to the environment in use.

For the layer calculation, no doubt you are using a lat long / degrees CRS and so the result is fraction of degrees.

For the canvas and the tools which work with the canvas, no doubt the setting is for a UTM CRS which uses metres as units.

hth

Willy
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    There seems to be some room for doubt: 0.004008cos(latitude)(1.85260)^2=49.4894km^2 at latitude=0, and there's no latitude where the area will be 1.017* bigger than the equatorial area in decimalDegrees^2. – Dave X Jan 14 '15 at 18:10