[GRASS-user] r.topidx - area of the hillslope per unit contour length

[Margherita Di Leo]

Ciao Pierluigi,

On Thu, Feb 28, 2013 at 12:17 PM, Ing. Pierluigi De Rosa <
pierluigi.derosa at gfosservices.it> wrote:

> Dear All,
> I should calculate  the area of the hillslope per unit contour length.
>

The drainage area per unit contour length (specific catchment area), can be
calculated by multiplying the upslope area obtained by r.watershed (flow
accumulation) per the cell grid size (as contour length).

HTH,
madi


> I saw r.topidx calculate topographic index (wetness index),
> ln(a/tan(beta)), map from elevation map  where
> a: the area of the hillslope per unit contour length that drains through
> any point,
> tan(beta): the local surface topographic slope (delta vertical) / (delta
> horizontal).
>
> I should only have the numerator of topographic index. How can i get it?
> Thanks
> Pierluigi
>
> --
>
>
> ________________________________________________________________________
> Ing. Pierluigi De Rosa (PhD)
> Studio Associato GFOSSERVICES
>
> Via Tilli 58 - 06127 Perugia (PG)
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> skype: pierluigi.derosa
>
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-- 
Margherita DI LEO
Postdoctoral Researcher

European Commission - DG JRC
Institute for Environment and Sustainability (IES). Unit H03 – FRC
Via Fermi, 2749
I-21027 Ispra (VA) - Italy - TP 261

Tel. +39 0332 78 3600
margherita.di-leo at jrc.ec.europa.eu

Disclaimer: The views expressed are purely those of the writer and may not
in any circumstance be regarded as stating an official position of the
European Commission.
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