Hi I would like to simply calculate areas of a area-shape file in square meters or in acres (ha).
I didn't find that functionality in the vector tools.
Could anyone here help me with that?
Make the layer editable, then use the field calculator (Layer>Open attribute table>Field Calculator/Ctrl+I or right click shapefile>Open attribute table>Field Calculator/Ctrl+I). There is an operator "$area" that will calculate the area of each row in the table. All units will be calculated in the units of the projection, so you probably want to project it to a projection that uses feet or metres before doing that, rather than lat/lon.
This can also be done with Vector|Geometry Tools|Add/export geometry columns, which creates a new shapefile with area and perimeter (or length) columns added.
Edit: (using the tool above, you can also unselect "save as new shape-file" in V1.8, the shapefile is now only updated!)
Using the field calculator is probably a better idea, though, as it doesn't require the creation of a new shapefile.
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