[GRASS-user] Re: Perimeter of lakes

[Hamish]

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