> Update 2... The exhaustive check gives the following misses:
wow ...indeed "a mess of bad triangles".
TSP publications reach back to before the 1950s and IIRC the data was mostly taken from German or Swiss cities.
17 cities is a rather small and surely old example and I think at that time they just copied the kilometers from a tourist guide or train schedule or similar, w/o taking much care.
So my theory was that just reaching the city limits naturally causes an error for large communities like Berlin or Zürich.
But I don't think it's worth to try to correct this now with something like a fuzzy surface in the visualization, better try starting from the beginning with real coordinates.
At least I think questioning the quality in my first reply was justified, it's worth checking data before trying to work with it.
( addicted to the Perl Programming Language)