[Qgis-user] Calculate Areas for Vector Overlays

[yanoff at tularosa.net]

Is there an efficient way to calculate areas of polygons in one vector layer
(shapefile) that intersect polygons in another vector layer?

For example, overlaying a nature preserve shapefile onto a land ownership
shapefile, I want to know the summed areas (e.g., ha) of each preserve in
each ownership.  For example, Preserve-1 is 10,000 ha private, 1000 ha
government, etc.

One way to do this is to intersect the two shapefiles (Vector >
Geoprocessing Tools > Intersect), which creates a new shapefile, and then
extract results from the new shapefile's attribute table. However, this is
time consuming.

There is a Tabulate Areas function in ArcGIS that performs a similar
function, where you can choose the fields to sum on (e.g., preserve name,
ownership), that performs an internal raster overlay and outputs a table. 
But it is typically for rasters.  Also, someone previously asked if a
similar function exists in QGIS, but so far there were no replies.

Thanks!

Steven Yanoff



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