[GRASS-user] Determine surface areas

[ich at the-masterplan.net]

Hi!

I am still working on the extended problem and so far i have done the
following.
I created circles and sectors in autocad and imported the dxf file (first
one sector at a time).
The import didn't seem to work that well, so i converted lines to
boundaries and used v.clean to get areas, and inserted a centroid with
v.digit and created a rastermap with v.to.rast (source: val, and
featuretype area).
using the rastermap as mask I can use r.report or r.stats to get the
waterarea/watercells.

Because there are 160 of these areas i was wondering if there is a
possibility to use all of the areas at once (or at least more than one at
a time) assign some kind of an ID to every area and get the results
separately for every area.
trying to use more than one area at a time always got me the total stats
for all areas.

kindest regards
Nikolaus




> 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
>