within function gives wrong results

[gisdev1982]

Hi Team, While executing the following query it gives wrong results. This was tested in postgis version from 1.2.1 to 1.5.5. In all the versions it gives wrong results.

Query is: SELECT within(geomfromtext('POLYGON((61 34,66 34,66 31,61 31,61 34))',101), geomfromtext('POLYGON((62 48,83 48,83 29,55 29,55 33,62 48))',101))

It gives me 'f' as result where as it should be 't'

If I execute the same query by adding some precision as shown below it gives me correct result.

SELECT within(geomfromtext('POLYGON((61 34,66.0000001 34,66 31,61 31,61 34))',101), geomfromtext('POLYGON((62 48,83 48,83 29,55 29,55 33,62 48))',101))

kindly help me how I can get the correct result without adding the precision.

[robe]

I tested this on PostGIS 2.3 running GEOS 3.6.1 and it works fine.

POSTGIS="2.3.2 r15302" GEOS="3.6.1-CAPI-1.10.1 r4317" PROJ="Rel. 4.9.1, 04 March 2015" GDAL="GDAL 2.1.3, released 2017/20/01" LIBXML="2.7.8" LIBJSON="0.12" RASTER

SELECT ST_Within(st_geomfromtext('POLYGON((61 34,66 34,66 31,61 31,61 34))',101), st_geomfromtext('POLYGON((62 48,83 48,83 29,55 29,55 33,62 48))',101));

st_within

---

t

(1 row)

Which version of GEOS are you running? I suspect upgrading your GEOS might do the trick.

Two reasons why we won't fix this:

1) It's likely this is a GEOS bug, not a PostGIS bug

2) PostGIS 1.5, we at best make only security patches on a version that old.

[robe]

More information. I happen to have a PostGIS 1.5.5 lying around and get true on that:

SELECT postgis_full_version();

POSTGIS="1.5.5" GEOS="3.3.8-CAPI-1.7.8" PROJ="Rel. 4.6.1, 21 August 2008" LIBXML="2.7.8" 

SELECT ST_Within(st_geomfromtext('POLYGON((61 34,66 34,66 31,61 31,61 34))',101), st_geomfromtext('POLYGON((62 48,83 48,83 29,55 29,55 33,62 48))',101));

st_within
----------
t

So seems your problem might be with GEOS. Upgrade your GEOS and see if it fixes your issue.