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 _______________________________________________ Qgis-user mailing list Qgis-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/qgis-user