[postgis-tickets] [PostGIS] #3572: ST_ClusterDBSCAN shouldn't join clusters by their borders

[PostGIS]

#3572: ST_ClusterDBSCAN shouldn't join clusters by their borders
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 Reporter:  dbaston  |      Owner:  dbaston
     Type:  defect   |     Status:  new
 Priority:  high     |  Milestone:  PostGIS 2.3.0
Component:  postgis  |    Version:  trunk
 Keywords:           |
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 In the DBSCAN algorithm, elements of a cluster are either
 * "core geometries", which are within {{{eps}}} distance of
 {{{minPoints}}} other geometries, or
 * "border geometries", which are within {{{eps}}} distance of a core
 geometry

 This leads to a situation where a (border) geometry {{{g}}} may not be
 within {{{eps}}} distance of {{{minPoints}}} other geometries, but ''is''
 within {{{eps}}} distance of core geometries in two or more different
 clusters {{{A}}}, {{{B}}}, .... etc.  In this case, rather than merging
 clusters {{{A}}} and {{{B}}} into a single cluster, {{{g}}} should be
 assigned arbitrarily but deterministically to either {{{A}}} or {{{B}}},
 which should remain separate.

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Ticket URL: <https://trac.osgeo.org/postgis/ticket/3572>
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