Improve performance of bottleneck area calculation Avoid buffer calculations by replacing them with simple distance comparisons and calculate the boundary of the result geometry only once per iteration. In some edge cases with very large numbers of iterations, this reduced the runtime of a bottleneck import by a factor of more than twenty.

teichmann@intevation.de = sascha.teichmann@intevation.de
bernhard.reiter@intevation.de = bernhard@intevation.de