[postgis-users] intersections strange behavior
franco base
frenk.calza at gmail.com
Wed May 30 09:18:59 PDT 2018
it works.
thanks a lot
2018-05-30 17:28 GMT+02:00 Marcin Mionskowski <mionskowskimarcin at gmail.com>:
> Try with ST_SnapToGrid:
> ST_SnapToGrid('your geom',0.000001)
> Vertex coordinates are doubles - even if it seems, that thay are the same
> in binary, thay can differ a bit, causing strange intersection results.
>
> Regards,
> Marcin
>
>
> On Wed, 30 May 2018 13:59:28 +0200, franco base <frenk.calza at gmail.com>
> wrote:
>
> Hi all,
>>
>> maybe this example is easier to understand.
>>
>> I cannot explain why
>> intersection between 2 line geometry return point (this is not true)
>> and
>> intersection between 2 same geometry transformed to WKT and then again to
>> geometry return line (this is true)
>>
>>
>>
>> WITH geom AS
>> (
>> SELECT
>>
>> ---- linestring geometry
>> '0102000020E610000002000000F1CB9E90EF5822400B08BFE04DB846408
>> 9928BE6E8582240A6DE39B92DB84640'::geometry(linestring,4326)
>> as a0,
>> '0102000020E610000003000000F4CB9E90EF5822400808BFE04DB846408
>> 9928BE6E8582240A6DE39B92DB846408C928BE6E8582240A9DE39B92DB84640'
>> ::geometry(linestring,4326) as b0,
>> ---------
>>
>> ---- makegeometry from output coordinate of ST_AsText
>> ST_GeomFromText
>> (ST_AsText('0102000020E610000002000000F1CB9E90EF5822400B08BF
>> E04DB8464089928BE6E8582240A6DE39B92DB84640'::geometry(linestring,4326)))
>> as a1,
>> ST_GeomFromText
>> (ST_AsText('0102000020E610000003000000F4CB9E90EF5822400808BF
>> E04DB8464089928BE6E8582240A6DE39B92DB846408C928BE6E8582240A9
>> DE39B92DB84640'::geometry(linestring,4326)))
>> as b1,
>> ---------
>>
>> ---- get point coordinate from linestring geometry
>> ST_AsText('0102000020E610000002000000F1CB9E90EF5822400B08BFE
>> 04DB8464089928BE6E8582240A6DE39B92DB84640'::geometry(linestring,4326))
>> as a,
>> ST_AsText('0102000020E610000003000000F4CB9E90EF5822400808BFE
>> 04DB8464089928BE6E8582240A6DE39B92DB846408C928BE6E8582240A9D
>> E39B92DB84640'
>> ::geometry(linestring,4326) ) as b
>> ----------
>> )
>>
>>
>> SELECT
>> st_geometrytype(st_intersection(a0,b0)),st_geometrytype(st_
>> intersection(a1,b1)),a,b
>> FROM geom
>>
>> RETURN
>> "ST_Point";"ST_LineString";"LINESTRING(9.17370273531376
>> 45.4398766453524,9.17365189031377
>> 45.4388953716819)";"LINESTRING(9.17370273531376
>> 45.4398766453524,9.17365189031377 45.4388953716819,9.17365189031377
>> 45.4388953716819)"
>>
>>
>>
>> "POSTGIS="2.2.1 r14555" GEOS="3.5.0-CAPI-1.9.0 r4084" PROJ="Rel. 4.9.2, 08
>> September 2015" GDAL="GDAL 1.11.3, released 2015/09/16" LIBXML="2.9.3"
>> LIBJSON="0.11.99" TOPOLOGY RASTER"
>>
>>
>>
>> Thanks a lot
>> f
>>
>>
>>
>> 2018-05-29 12:49 GMT+02:00 franco base <frenk.calza at gmail.com>:
>>
>> Thanks I undesrtand.
>>> Infact
>>>
>>> SELECT st_contains(b,a) return true.
>>>
>>>
>>> I still don't understand why
>>>
>>> SELECT st_intersection(a,b) return a line
>>> and
>>> SELECT st_intersection(a,c) return a point
>>> and
>>> SELECT st_intersection(b,c) return a point
>>>
>>>
>>>
>>> SELECT ST_AsText (c)
>>>
>>> return
>>>
>>> "LINESTRING(*9.18334214253396 45.4443310195606,9.18284350788197
>>> 45.4441804010334,9.18274220788201 45.4441483010334,9.18274220788201
>>> 45.4441483010334,9.18271080788202 45.4441388010335,9.18271080788202
>>> 45.4441388010335*,9.18267210788205 45.4442348010335,9.18267210788205
>>>
>>> 45.4442348010335,9.18256900788209 45.4442025010335,9.18256930788208
>>> 45.4442020010335,9.1817161078824 45.4439402010335,9.1817161078824
>>> 45.4439402010335,9.18096850788267 45.4437069010336,9.18096850788267
>>> 45.4437069010336,9.18075270788275 45.4436465010336,9.18075270788275
>>> 45.4436465010336,9.18046820788286 45.4435903010337,9.18046820788286
>>> 45.4435903010337,9.18017890788296 45.4435440010337,9.18017890788296
>>> 45.4435440010337,9.17996920788304 45.4435166010337,9.17996920788304
>>> 45.4435166010337,9.17973530788314 45.4435053010337,9.17973530788314
>>> 45.4435053010337,9.17950020788323 45.4435044010337,9.17950020788323
>>> 45.4435044010337,9.17913950788338 45.4435149010338,9.17913950788338
>>> 45.4435149010338,9.17903360788343 45.4435180010338,9.17903360788343
>>> 45.4435180010338,9.17900690788344 45.4435188010338,9.17900690788344
>>> 45.4435188010338,9.17898210788345 45.4435200010338,9.17898210788345
>>> 45.4435200010338,9.17890050788348 45.4435241010338,9.17890050788348
>>> 45.4435241010338,9.17876780788353 45.4435307010338,9.17847140788366
>>> 45.4435455010338,9.17875697558416 45.4435312419178)"
>>>
>>> The first 6 point are the same that make b geometry
>>>
>>> >> st_makepoint(9.18334214253396,45.4443310195606),
>>> >> st_makepoint(9.18284350788197,45.4441804010334),
>>> >> st_makepoint(9.18274220788201,45.4441483010334),
>>> >> st_makepoint(9.18274220788201,45.4441483010334),
>>> >> st_makepoint(9.18271080788202,45.4441388010335),
>>> >> st_makepoint(9.18271080788202,45.4441388010335)
>>>
>>> The first 2 point are the same that make a geometry
>>> >> st_makepoint(9.18284350788197,45.4441804010334),
>>> >> st_makepoint(9.18334214253396,45.4443310195606)
>>>
>>>
>>>
>>> thanks
>>> f
>>>
>>>
>>>
>>>
>>>
>>>
>>> 2018-05-28 21:22 GMT+02:00 Paul Ramsey <pramsey at cleverelephant.ca>:
>>>
>>> Also knowing that the end points of a line string are considered the
>>>> boundary of the linestring, not the interior...
>>>>
>>>> On Mon, May 28, 2018 at 12:21 PM, Paul Ramsey <
>>>> pramsey at cleverelephant.ca>
>>>> wrote:
>>>> > Does knowing that an overlaps test is only true if the interiors of
>>>> > both objects interact, but there is no full containment relationship
>>>> > help you understand a little?
>>>> >
>>>> > On Mon, May 28, 2018 at 8:03 AM, franco base <frenk.calza at gmail.com>
>>>> wrote:
>>>> >> Hi all,
>>>> >>
>>>> >>
>>>> >> question 1)
>>>> >> why ST_Overlaps doesn't work with geometry a and b?
>>>> >> The first 2 point of the 2 line (bold) are the same.
>>>> >> ST_Intersection works
>>>> >>
>>>> >> question 2)
>>>> >> if I extend line b it becomes c
>>>> >> (sorry i write text geometry because I have a lot of point coord),
>>>> >> ST_Overlaps return false and also
>>>> >> ST_Intersection return a point (length =0)
>>>> >>
>>>> >> What's happen?
>>>> >>
>>>> >> "POSTGIS="2.2.1 r14555" GEOS="3.5.0-CAPI-1.9.0 r4084" PROJ="Rel.
>>>> 4.9.2, 08
>>>> >> September 2015" GDAL="GDAL 1.11.3, released 2015/09/16"
>>>> LIBXML="2.9.3"
>>>> >> LIBJSON="0.11.99" TOPOLOGY RASTER"
>>>> >>
>>>> >>
>>>> >> WITH geom AS
>>>> >> (
>>>> >> SELECT
>>>> >> st_setsrid(st_makeline(
>>>> >> st_makepoint(9.18284350788197,45.4441804010334),
>>>> >> st_makepoint(9.18334214253396,45.4443310195606)
>>>> >> ),4326) a,
>>>> >>
>>>> >> st_setsrid(st_makeline(ARRAY[
>>>> >> st_makepoint(9.18334214253396,45.4443310195606),
>>>> >> st_makepoint(9.18284350788197,45.4441804010334),
>>>> >> st_makepoint(9.18274220788201,45.4441483010334),
>>>> >> st_makepoint(9.18274220788201,45.4441483010334),
>>>> >> st_makepoint(9.18271080788202,45.4441388010335),
>>>> >> st_makepoint(9.18271080788202,45.4441388010335) ]),4326) b,
>>>> >>
>>>> >> '0102000020E610000027000000E8527405DF5D224039CEBED6DFB846402
>>>> A470DAA9D5D22403CFB43E7DAB8464073E7FC62905D22409DC1FDD9D9B84
>>>> 64073E7FC62905D22409DC1FDD9D9B8464040F560458C5D224065A94C8AD
>>>> 9B8464040F560458C5D224065A94C8AD9B84640577DD232875D224085179
>>>> BAFDCB84640577DD232875D224085179BAFDCB84640C43B5CAF795D2240B
>>>> B5EA7A0DBB84640BB366DB9795D2240D5A0759CDBB84640CB05C9E4095D2
>>>> 240CC685208D3B84640CB05C9E4095D2240CC685208D3B8464088EC7DE7A
>>>> 75C224074794263CBB8464088EC7DE7A75C224074794263CBB84640280A7
>>>> 29E8B5C224050769668C9B84640280A729E8B5C224050769668C9B846403
>>>> 1A63554665C224097E12591C7B8464031A63554665C224097E12591C7B84
>>>> 6409A92E968405C22406A63C10CC6B846409A92E968405C22406A63C10CC
>>>> 6B84640164A8CEC245C22402356E826C5B84640164A8CEC245C22402356E
>>>> 826C5B84640D4962A44065C22406FC51DC8C4B84640D4962A44065C22406
>>>> FC51DC8C4B84640A5F78473E75B2240380991C0C4B84640A5F78473E75B2
>>>> 240380991C0C4B84640B08F6F2CB85B2240449DA518C5B84640B08F6F2CB
>>>> 85B2240449DA518C5B84640087D054BAA5B224050D0A632C5B84640087D0
>>>> 54BAA5B224050D0A632C5B84640213C1ECBA65B2240F2CC5C39C5B846402
>>>> 13C1ECBA65B2240F2CC5C39C5B846406BDBF78AA35B2240F0C76D43C5B84
>>>> 6406BDBF78AA35B2240F0C76D43C5B84640D731EDD8985B2240C676D265C
>>>> 5B84640D731EDD8985B2240C676D265C5B84640EFDF4074875B224027DB2
>>>> F9DC5B846404443B89A605B2240369D5619C6B84640B521C808865B22404
>>>> 765B9A1C5B84640'::geometry
>>>> >> as c
>>>> >> )
>>>> >>
>>>> >>
>>>> >> SELECT
>>>> >> ---- question 1
>>>> >> st_overlaps(a,b),
>>>> >> st_length(st_intersection(a,b)::geography)::int,
>>>> >> ---- question 2
>>>> >> st_overlaps(a,c),
>>>> >> st_length(st_intersection(a,c)::geography)::int
>>>> >>
>>>> >> FROM geom
>>>> >>
>>>> >>
>>>> >> return
>>>> >>
>>>> >> f;42;f;0
>>>> >>
>>>> >>
>>>> >>
>>>> >> thanks
>>>> >> ft
>>>> >>
>>>> >>
>>>> >>
>>>> >>
>>>> >>
>>>> >>
>>>> >>
>>>> >> _______________________________________________
>>>> >> postgis-users mailing list
>>>> >> postgis-users at lists.osgeo.org
>>>> >> https://lists.osgeo.org/mailman/listinfo/postgis-users
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>>>>
>>>
>>>
>>
>
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