Sinuosity of Kemijoki: Difference between revisions

Revision as of 09:36, 27 April 2026

Use Python to estimate the sinuosity of Kemijoki.

The river was obtained from https://download.geofabrik.de/europe/finland.html but only one river (Kemijoki) with one branch is used. The extracting method is described elsewhere.

Kemijoki is 550 km long according to Wikipedia. This dataset contains 500.20 km of river.
Kemijoki measured with 50 km measure stick. The distance doesn't exactly match up, and the last 12 km is missing.
By cutting the measuring stick to half, we get one measure (25 km) more length. It still skips many of the meandering.
More distance and curves are achieved.
Missing only 1 km, but because the river curves so eccentric, it skips many kilmometers. By zooming it is easy to see that a lot of meandering is missing.
Taking 2.5 km out of the measuring stick, we gain 30 km of river length.
Finally, using a 100 m strides we will arrive rather close to the GIS measure.
The length vs radius. Note the sawtooth phenomena.

Douglas-Peucker simplification at different tolerances

The fractal dimension is defined by $N=\epsilon ^{-d}$ which gives $d=-{\frac {\log N}{\log \epsilon }}$ .

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 Douglas-Peucker simplification at different tolerances
+== Fractal Dimension ==
+The fractal dimension is defined by <math>N = \epsilon^{-d}</math> which gives <math>d = - \frac{\log N}{\log \epsilon}</math>.