[GRASS-user] How to find elevation drop for all cells in a basin

[Thomas Adams]

Hi Ken,

So, if I understand, that seems pretty simple and could be done with
r.mapcalc:

diff = elev - outlet_elev

where elev is a raster map of elevations and outlet_elev is the elevation
at the basin outlet. Using a basin mask the calculation could be confined
to any basin of interest. But, I am probably missing something, I think…

Tom

On Tue, Dec 15, 2020 at 2:51 PM Ken Mankoff <mankoff at gmail.com> wrote:

> Hi Thomas,
>
> On 2020-12-15 at 11:34 -08, Thomas Adams <tea3rd at gmail.com> wrote...
> > What exactly do you mean by elevation drop (at each cell)? I can only
> guess…
>
> I meant the change in each cell between their elevation and the elevation
> of the associated hydrologic outlet cell.
>
> I actually need to query a different raster than change in elevation, but
> it seems like I can pass any cost surface I want as the elevation parameter
> to r.stream.distance and it works. I think it uses the input direction
> raster to calculate the outlet for each source, then queries the input and
> output "elevation" raster (in my case some other cost surface), regardless
> of what those values represent.
>
>   -k.
>
>

-- 
Thomas E Adams, III
1724 Sage Lane
Blacksburg, VA 24060
tea3rd at gmail.com (personal)
tea at terrapredictions.org (work)

1 (513) 739-9512 (cell)
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