[GRASS-user] Determine surface areas

[ich at the-masterplan.net]

Hi!

Thanks a lot for the quick responses.
It worked fine with - v.buffer, v.to.rast, r.mask, r.mapcalc /
"watercells" = if (landcover==water,1,null()) and r.sum rast="watercells"

I am still trying to get it to work with v.rast.stats (program is asking
for a database connection and i don't know, what the column prefix might
be)

An additional request for my work would be to separate the circle into
orientations meaning making 4 circle-segments (North, East, South, West).
As far is I understand, v.buffer would only create "some space" around the
created vector point. The first thing I would think of is creating 4
"Angle-maps"-Masks and combine them with the buffer circle. Does this seem
possible?

Thanks again for your help
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
>