08 Dec 2008, 23:58
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Michael Neubauer (3 posts)

Hello Gary,

I loaded you “world border” shape file in QGIS. Everything works fine. But when I click with the identifying tool in one of the countries it always gives me a slightly different area derived than what is given in the attribute table: example: Area derived: 494.033,400 km2 attribute table: Area: 504782 (without unit, but I guess it is km2 as well)

where does this difference come from?

But thanks a lot for this very good book!

07 Dec 2008, 01:20
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Gary Sherman (7 posts)

There are a couple of reasons for the difference:

  1. The AREA attribute may be based on the actual area of the country rather than a “GIS” area. The resolution of the data may not be adequate to capture the true area.

  2. If you have projected the data (which it looks like you may have) and are not using an equal area projection the numbers will be a bit different.

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