[GRASS-user] Determine surface areas

[Moritz Lennert]

On 27/02/09 09:53, Nikolaus Arnold wrote:
> Hi!
> 
> I am new to using GIS and GRASS.
> I am currently working on a task where I have to determine the type of 
> surface around a specific coordinate. For example what is the total 
> water surface area in a 100km radius around the Eiffeltower.
> I have found a landcover map ( 
> http://glcf.umiacs.umd.edu/data/landcover/ ) with a 1km raster that 
> isn't perfect but should do the job.

If it is for Europe, you might want to check out Corine Landcover [1] 
which has a resolution of 1 ha.

> After some time I managed 
> displaying the map and showing only specific values in GRASS. My next 
> step would have been exporting the map to an image, draw the desired 
> circles with a image editing tool and count the contained fields manually.
> But taking a closer look at GRASS and the vectormap function, I wondered 
> if it would be possible to create vector circles, merge them with the 
> existing map and let GRASS do the work of counting the Areas.
> 
> Does this seem possible? If yes, what would be the first steps?

1) Use buffering to create desired buffers: r.buffer or v.buffer 
(possibly + v.to.rast)

2) Calculate statistics of land use per buffer: r.stats, r.report if you 
use raster buffers, v.rast.stats if you use vector buffers

Moritz

[1]http://dataservice.eea.europa.eu/dataservice/metadetails.asp?id=1007 
and http://www.eea.europa.eu/themes/landuse/clc-download