I would like to create a new shapefile from another area shapefile. The new shapefile should only contain all areas that are bigger than 5 acres (10.000 m²).
How do I do this?
Select all areas bigger than 10,000 m2. Either:
area > 10000in the "SQL where clause" box, and click OK.
Close the attribute table and then select Layer|Save selection as vector file.
Option 2 above is probably better practice - you avoid making errors clicking and shift-clicking in the table, and it will be far quicker for a dataset with a lot of rows.
There is a way that could be a little quicker as it uses a faster method to query the data.
area > 10000
This uses the underlying data provider, in this case ogr, to query the data which in most cases is faster then using the search functions inside QGIS via the attribute table.