[GRASS-user] Re: Perimeter of lakes
Hamish
hamish_b at yahoo.com
Sat Dec 4 17:37:17 EST 2010
Emma wrote:
> Is there a way to calculate from the DEM the total perimeter of
> all lakes (+reservoirs, etc.)? In other words, I need to
> calculate the total length of lake banks and so far could only
> determine the total lakes area, which is of no use in this
> case.
It's a fractal problem and so an impossible task to get the right
answer to. The best you can do is compare the relative perimeter
distances within the dataset (eg lake x has twice the shoreline
of lake y), but even then only if you can verify that the
original dataset is entirely consistent in its level of detail &
digitization.
see
http://en.wikipedia.org/wiki/How_Long_Is_the_Coast_of_Britain%3F_Statistical_Self-Similarity_and_Fractional_Dimension
which is to say, you're probably going to have to consider your
problem in another way.
maybe you could calculate the plan-area of the littoral strip in
a 5m(?) buffer around each one of the lakes and reservoirs?
Hamish
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