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

[Marco]

Solved

Thank you. 
I found good solutions. .
gvSIG is part of it. It delivers straightforwardly the minimum circle and minimum rectangle for a group of points (the vertices) per class of points (number of polygon). 

Cheers,
Marco


________________________________
 From: Margherita Di Leo <diregola at gmail.com>
To: Marco <marco_gjv at ymail.com> 
Cc: "grass-user at lists.osgeo.org" <grass-user at lists.osgeo.org> 
Sent: Thursday, June 7, 2012 1:26 PM
Subject: Re: [GRASS-user] r.basin ? for plane geometry of polygon shapefiles
 

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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