Hi Gerd The bench in lake problem is avoided by the user not using the merge-at -mid-point option. Possibly making the delete-poi option keep the most central one and delete the rest. Ticker On Thu, 2020-05-07 at 09:12 +0000, Gerd Petermann wrote:
Hi Ticker,
I should have used amenity=bench in the example, this is a bit more realistic, but the default style doesn't generate a POI for that.
I've found a rather simple iterative algo to fix the problem, but what I really wanted to point out is that the result can look really wrong. Benches are often arranged around something, e.g. a small lake/pond. I think nobody wants a map that shows a bench in the middle of a lake. OTHO, bus stops typically come in pairs, but maybe 50m apart. It seems reasonable to merge them in the middle.
Gerd
________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von Ticker Berkin <rwb-mkgmap@jagit.co.uk> Gesendet: Donnerstag, 7. Mai 2020 10:21 An: Development list for mkgmap Betreff: Re: [mkgmap-dev] nearby-POI: What to do with several POI arranged on a circle?
Hi
The problem is in the point grouping algo, rather than anything to do with the merge-at-mid-point option.
Although an interesting problem to solve, it seems to be getting excessive. The simple logic in the last versions seemed to solve most users's problems and make them happy.
Ticker
On Thu, 2020-05-07 at 07:42 +0000, Gerd Petermann wrote:
Hi all,
while doing further tests I've found this edge case (see attached file) Draw a circle with a diameter of ~56m and tag all nodes amenity=bank. The default style has amenity=bank [0x2f06 resolution 24]
With --nearby-poi-rules=0x2f06:30:merge-at-mid-point one might expect a single POI in the middle of the circle, but the result is different: Since there is no POI near the center of the circle the current algo finds 4 groups, all close to the edge of the circle.
I think for merge-at-mid-point I need a different algo. I'm looking at https://en.wikipedia.org/wiki/Cluster_analysis now.
Gerd
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