[Django] #27971: GeoDjango LinearRing and Polygon handle contains/covers differently

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Mar 21, 2017, 1:11:48 PM3/21/17

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#27971: GeoDjango LinearRing and Polygon handle contains/covers differently
-------------------------------------+-------------------------------------
Reporter: Geoffrey | Owner: nobody
Fairchild |
Type: Bug | Status: new
Component: GIS | Version: 1.10
Severity: Normal | Keywords: GeoDjango,
| LinearRing, Polygon, covers,
Triage Stage: | contains
Unreviewed | Has patch: 0
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
-------------------------------------+-------------------------------------
I'm running Python 3.6.0 and Django 1.10.6. I'm seeing a difference in how
the
[[https://docs.djangoproject.com/en/1.10/ref/contrib/gis/geos/#linearring|LinearRing]]
and
[[https://docs.djangoproject.com/en/1.10/ref/contrib/gis/geos/#polygon|Polygon]]
types deal with the
[[https://docs.djangoproject.com/en/1.10/ref/contrib/gis/geos/#django.contrib.gis.geos.GEOSGeometry.contains|contains]]
and
[[https://docs.djangoproject.com/en/1.10/ref/contrib/gis/geos/#django.contrib.gis.geos.GEOSGeometry.covers|covers]]
methods. The gist is that `LinearRing` objects seem ''not'' to properly
handle `contains`/`covers`, while `Polygon` objects do. See the following
example:

{{{
> python
Python 3.6.0 (default, Mar 6 2017, 11:41:46)
[GCC 4.2.1 Compatible Apple LLVM 8.0.0 (clang-800.0.42.1)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> from django.contrib.gis.geos import GEOSGeometry
>>> aruba = GEOSGeometry('SRID=4326;LINEARRING (-69.89912109375
12.45200195312499, -69.895703125 12.42299804687499, -69.94218749999999
12.43852539062499, -70.004150390625 12.50048828125, -70.06611328125
12.54697265624999, -70.05087890624999 12.59707031249999, -70.035107421875
12.61411132812499, -69.97314453125 12.567626953125, -69.91181640625
12.48046875, -69.89912109375 12.45200195312499)')
>>> print(aruba)
SRID=4326;LINEARRING (-69.89912109375 12.45200195312499, -69.895703125
12.42299804687499, -69.94218749999999 12.43852539062499, -70.004150390625
12.50048828125, -70.06611328125 12.54697265624999, -70.05087890624999
12.59707031249999, -70.035107421875 12.61411132812499, -69.97314453125
12.567626953125, -69.91181640625 12.48046875, -69.89912109375
12.45200195312499)
>>> point = GEOSGeometry('POINT (-69.95647745161588 12.48564548990554)')
>>> print(point)
POINT (-69.95647745161588 12.48564548990554)
>>> aruba.contains(point)
False
>>> aruba.covers(point)
False
>>> aruba = GEOSGeometry('SRID=4326;POLYGON ((-69.89912109375
12.45200195312499, -69.895703125 12.42299804687499, -69.94218749999999
12.43852539062499, -70.004150390625 12.50048828125, -70.06611328125
12.54697265624999, -70.05087890624999 12.59707031249999, -70.035107421875
12.61411132812499, -69.97314453125 12.567626953125, -69.91181640625
12.48046875, -69.89912109375 12.45200195312499))')
>>> print(aruba)
SRID=4326;POLYGON ((-69.89912109375 12.45200195312499, -69.895703125
12.42299804687499, -69.94218749999999 12.43852539062499, -70.004150390625
12.50048828125, -70.06611328125 12.54697265624999, -70.05087890624999
12.59707031249999, -70.035107421875 12.61411132812499, -69.97314453125
12.567626953125, -69.91181640625 12.48046875, -69.89912109375
12.45200195312499))
>>> aruba.contains(point)
True
>>> aruba.covers(point)
True
}}}

For what it's worth, while writing this issue, I just discovered that
Shapely, which also relies on GEOS, displays the same behavior:

{{{
> python
Python 3.6.0 (default, Mar 6 2017, 11:41:46)
[GCC 4.2.1 Compatible Apple LLVM 8.0.0 (clang-800.0.42.1)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> from shapely.geometry.polygon import LinearRing, Polygon
>>> from shapely.geometry import Point
>>> aruba = LinearRing([(-69.89912109375, 12.45200195312499),
(-69.895703125, 12.42299804687499), (-69.94218749999999,
12.43852539062499), (-70.004150390625, 12.50048828125), (-70.06611328125,
12.54697265624999), (-70.05087890624999, 12.59707031249999),
(-70.035107421875, 12.61411132812499), (-69.97314453125, 12.567626953125),
(-69.91181640625, 12.48046875), (-69.89912109375, 12.45200195312499)])
>>> print(aruba)
LINEARRING (-69.89912109375 12.45200195312499, -69.895703125
12.42299804687499, -69.94218749999999 12.43852539062499, -70.004150390625
12.50048828125, -70.06611328125 12.54697265624999, -70.05087890624999
12.59707031249999, -70.035107421875 12.61411132812499, -69.97314453125
12.567626953125, -69.91181640625 12.48046875, -69.89912109375
12.45200195312499)
>>> point = Point(-69.95647745161588, 12.48564548990554)
>>> print(point)
POINT (-69.95647745161588 12.48564548990554)
>>> aruba.contains(point)
False
>>> aruba = Polygon([(-69.89912109375, 12.45200195312499), (-69.895703125,
12.42299804687499), (-69.94218749999999, 12.43852539062499),
(-70.004150390625, 12.50048828125), (-70.06611328125, 12.54697265624999),
(-70.05087890624999, 12.59707031249999), (-70.035107421875,
12.61411132812499), (-69.97314453125, 12.567626953125), (-69.91181640625,
12.48046875), (-69.89912109375, 12.45200195312499)])
>>> print(aruba)
POLYGON ((-69.89912109375 12.45200195312499, -69.895703125
12.42299804687499, -69.94218749999999 12.43852539062499, -70.004150390625
12.50048828125, -70.06611328125 12.54697265624999, -70.05087890624999
12.59707031249999, -70.035107421875 12.61411132812499, -69.97314453125
12.567626953125, -69.91181640625 12.48046875, -69.89912109375
12.45200195312499))
>>> aruba.contains(point)
True
}}}

Is this a bug (perhaps a GEOS bug since both Shapely and GeoDjango display
the same behavior), or is this to be expected (i.e., am I misunderstanding
some fundamental concept about `LinearRing`s)?

--
Ticket URL: <https://code.djangoproject.com/ticket/27971>
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Mar 21, 2017, 1:40:35 PM3/21/17

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#27971: GeoDjango LinearRing and Polygon handle contains/covers differently
-------------------------------------+-------------------------------------

Reporter: Geoffrey Fairchild | Owner: nobody

Type: Bug | Status: new
Component: GIS | Version: 1.10

Severity: Normal | Resolution:
Keywords: GeoDjango, | Triage Stage:
LinearRing, Polygon, covers, | Unreviewed
contains |

Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------

Comment (by Geoffrey Fairchild):

Search results for this topic seem sparse. Interestingly, I can compute
centroids for ''both'' LinearRings and Polygons:

>>> print(aruba.centroid)
SRID=4326;POINT (-69.97885392271023 12.51632637412778)

>>> aruba = GEOSGeometry('SRID=4326;POLYGON ((-69.89912109375
12.45200195312499, -69.895703125 12.42299804687499, -69.94218749999999
12.43852539062499, -70.004150390625 12.50048828125, -70.06611328125
12.54697265624999, -70.05087890624999 12.59707031249999, -70.035107421875
12.61411132812499, -69.97314453125 12.567626953125, -69.91181640625
12.48046875, -69.89912109375 12.45200195312499))')
>>> print(aruba)
SRID=4326;POLYGON ((-69.89912109375 12.45200195312499, -69.895703125
12.42299804687499, -69.94218749999999 12.43852539062499, -70.004150390625
12.50048828125, -70.06611328125 12.54697265624999, -70.05087890624999
12.59707031249999, -70.035107421875 12.61411132812499, -69.97314453125
12.567626953125, -69.91181640625 12.48046875, -69.89912109375
12.45200195312499))

>>> print(aruba.centroid)
SRID=4326;POINT (-69.98267711250941 12.52088038384019)
}}}

If I can compute a centroid, why can't I compute whether another geometry
is interior to the LinearRing?

--
Ticket URL: <https://code.djangoproject.com/ticket/27971#comment:1>

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Mar 21, 2017, 1:55:37 PM3/21/17

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#27971: GeoDjango LinearRing and Polygon handle contains/covers differently
-------------------------------------+-------------------------------------

Reporter: Geoffrey Fairchild | Owner: nobody

Type: Bug | Status: closed
Component: GIS | Version: 1.10
Severity: Normal | Resolution: invalid

Keywords: GeoDjango, | Triage Stage:
LinearRing, Polygon, covers, | Unreviewed
contains |

Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------

Changes (by Sergey Fedoseev):

* status: new => closed
* resolution: => invalid

Comment:

LinearRing is a line, so it doesn't contain or cover the specified point.
Look at http://bl.ocks.org/d/51034db6faf00af30734b1e7e1b2bf03