[geos-devel] [GEOS] #1079: Inconsistent dimensionality change

[GEOS]

#1079: Inconsistent dimensionality change
------------------------+--------------------------
 Reporter:  Mike Taves  |      Owner:  geos-devel@…
     Type:  defect      |     Status:  new
 Priority:  minor       |  Milestone:  3.9.0
Component:  Default     |    Version:  master
 Severity:  Annoyance   |   Keywords:
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 Over in Shapely, there is a test suite
 [https://github.com/Toblerity/Shapely/blob/b2b536004ee6b8316fffcee36ff8e1e65be71958/tests/test_create_inconsistent_dimensionality.py
 test_create_inconsistent_dimensionality.py] that checks WKT with
 inconsistent dimensionality. For most instances, a geometry with at least
 one 3D coordinate is promoted with a Z dimension, assuming Z=0 for other
 XY coordinates. There are a few isolated cases where the geometry remains
 as a 2D geometry if the 3D coordinate is not the first.

 Of these inconsistencies, one new inconsistency stands out as new and
 unusual.

 GEOS 3.8.1 and earlier:
 {{{
 # preserve 3rd dimension
 LINESTRING (1 1 1, 2 2) -> LINESTRING Z (1 1 1, 2 2 0)
 # drop 3rd dimension
 LINESTRING (1 1, 2 2 2) -> LINESTRING (1 1, 2 2)
 }}}
 Since GEOS 3.9.0beta1:
 {{{
 # drop 3rd dimension
 LINESTRING (1 1 1, 2 2) -> LINESTRING (1 1, 2 2)
 # preserve 3rd dimension
 LINESTRING (1 1, 2 2 2) -> LINESTRING Z (1 1 0, 2 2 2)
 }}}
 why is this the only geometry type scenario that swaps behaviour? Ideally
 any geometry with at lest one 3D coordinate would be promoted with a Z
 dimension.

-- 
Ticket URL: <https://trac.osgeo.org/geos/ticket/1079>
GEOS <http://trac.osgeo.org/geos>
GEOS (Geometry Engine - Open Source) is a C++ port of the Java Topology Suite (JTS).