[GRASS-user] r.basin ? for plane geometry of polygon shapefiles

[Margherita Di Leo]

Marco,

On Thu, Jun 7, 2012 at 1:15 PM, Marco <marco_gjv at ymail.com> wrote:

> Hi Margherita,
>
> Grazie. Its not related to hydrology. I just want to get some shape
> indexes to characterize networks of polygons (periglacial patterned ground).
> I came to your Grass Add-on because the indexes used in 2D basin
> morphometry are really adequate to characterize each individual polygon.
>
> I have already used SAGA GIS and GVSig, which automatically supply shape
> parameters relating the perimeter of the polygon to its area in various
> ways. And that´s already fine information.
> From that I know if the polygon is more elongated or more circular. And
> maybe more information won´t add to much... But I still would like to try.
> Mainly because of the indexes which grab the axis and  which relate the
> polygon to and ideal shape.
>
> Maybe I should focus on doing one thing at a time: 1) axis calculation;
> and 2) deriving the ideal shape from the centroid of the polygon. Then
> I´d have great information.
>

Have you seen v.to.db[1]? It allows you to calculate some parameters such
as area, perimeter, compactness, fractal dimension, etc.

>
> My next step is to go inside you python code (of which I know little) and
> try to extract the relevant pieces.
>

The code is quite self-explanatory and the formulas are very simple so that
you could also calculate some parameters in a spreadsheet, anyways if you
need further information don't hesitate to ask.

>
> Thank you.
> Marco
> (gonna start a MSc related to cryosphere geomorphology next Fall)
>

Congrats ;-)

ciao madi

[1] http://grass.osgeo.org/gdp/html_grass64/v.to.db.html
-- 
Dr. Margherita Di Leo
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