[mkgmap-dev] nearby-POI: What to do with several POI arranged on a circle?

Thu May 7 15:04:21 BST 2020

Hi Randolph,

I try to find out what the result should be when more than two POI are involved. They may be arranged in a straight line or in a circle or whatever random order.
At the moment I tend to follow Tickers suggestion and remove the option to keep it simple.

Gerd

________________________________________
Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von Randolph J. Herber <army.bronze.star at gmail.com>
Gesendet: Donnerstag, 7. Mai 2020 15:21
An: mkgmap-dev at lists.mkgmap.org.uk
Betreff: Re: [mkgmap-dev] nearby-POI: What to do with several POI arranged on a circle?

Perhaps averaging the latitude and longitude coordinates of all the points separately would work. That is not quite the same as meet in the middle. If the points are evenly spaced around the edge of a circle, even though the latitude and longitude scalings (except at the equator) are not the same. What I believe you are trying to do is minimize the total distance from the selected point to the collection of points.

Randolph J. Herber

On 5/7/2020 2:42 AM, 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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