[GRASS-dev] any randomness in i.segment ?

[Markus Metz]

On Wed, Mar 28, 2018 at 3:04 PM, Moritz Lennert <
mlennert at club.worldonline.be> wrote:
>
> Hi,
>
> Working with a colleague and comparing results we were wondering whether
i.segment contains any randomness effects which might make results differ
from one run to another.

There is no randomness in i.segments. Given he same input data and
settings, results should be identical between runs, i.e. repeatable.

Did you do a simple diff with r.mapcalc?
>
> In the manual it says in section Seeds in the chapter on region growing:
>
> "The seeds map can be used to provide either seed pixels (random or
selected points from which to start the segmentation process) or seed
segments."
>
> which sounds as if the module creates random seeds if none are given.
Looking through the code, I do not find such creation of random seeds,
though. Is this just me not looking correctly, or aren't there any ?

A seed map can be created by randomly selecting pixels, e.g. with r.random.
If a seed map is not given, all non-NULL cells are seeds.

HTH,

Markus M

>
> Moritz
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