[GRASS-stats] How to give projection to polygons and calculate area

[Markus Metz]

On Tue, May 21, 2013 at 11:54 PM, Hamish <hamish_b at yahoo.com> wrote:
> Nicolás wrote:
>> I am working with GRASS functions in R batch job:
>> I need to calculate areas from polygons which are in a
>> geographical projection. To do so, i would like to define a new
>> projection (Lamert Azimutal Equal Area) to my polygons, and the
>> to calculate areas.
>
> raster areas or vector areas?
>
> (GRASS's r.* modules generally deal with that and give the
> correct area in sq-meters automatically, so no need to reproject;
> the v.* modules generally/often do not [yet])

A simple query by clicking on the polygon will give square meters for
latlon. v.to.db uploads values in meters or square meters for latlon,
or miles, feet, acres, hectares when requested.

Markus M

>
> if you'd like to make a new location in GRASS via a script,
> you can use the g.proj module to do that (-c flag), then use
> a GRASS_BATCH_JOB to automatically pull the vector map in with
> v.proj and do the calculation.
>
>
> Hamish
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