ST_Minkowski offset/translation?

[osgeoap]

Testing the ST_MinkowskiSum is producing an unexepected translated position for the geometry.

oid |extname |extowner|extnamespace|extrelocatable|extversion|extconfig|extc

---

13745|plpgsql | 10| 11|false |1.0 |NULL |NULL 79944|postgis | 10| 2200|false |3.2.0 |{80254} |{"WH 80982|mobilitydb | 10| 2200|false |1.1.0 |NULL |NULL

3694605|postgis_sfcgal| 10| 2200|true |3.2.0 |NULL |NULL

WITH T(id,trip) as (

SELECT 1,setsrid(tgeompoint '[Point(1000 1000)@2012-02-01T00:01:01, Point(1020 1010)@2012-02-01T00:01:02, Point(1040 1020)@2012-02-01T00:01:03]',3857) union all SELECT 2,setsrid(tgeompoint '[Point(1100 1000)@2012-02-01T00:01:05, Point(1120 1010)@2012-02-01T00:01:06, Point(1110 1020)@2012-02-01T00:01:08]',3857) union all SELECT 3,setsrid(tgeompoint '[Point(1200 1000)@2012-02-01T00:01:10, Point(1140 1010)@2012-02-01T00:01:20, Point(1160 1020)@2012-02-01T00:01:40]',3857)

) select

ST_AsEWKT(ST_Force2D(t1.trip::geometry)) as wkt_t1geom, ST_AsEWKT(ST_Force2D(t2.trip::geometry)) as wkt_t2geom, ST_AsEWKT(ST_MinkowskiSum(ST_Force2D(transform(t1.trip,3857)::geometry), ST_Buffer(ST_Force2D(transform(t1.trip,3857)::geometry),10))) —ST_AsEWKT(ST_MinkowskiSum( transform(t1.trip,3857)::geometry, transform(t2.trip,3857)::geometry ) as wkt_mink

FROM T t1, T t2 where t1.id < t2.id

create extension postgis_sfcgal;

wkt_t1geom |wkt_t2geom |st_asewkt |

---

SRID=3857;LINESTRING(1000 1000,1040 1020) |SRID=3857;LINESTRING(1100 1000,1120 1010,1110 1020)|SRID=3857;MULTIPOLYGON(((1990.0251579118735 1999.2911097990932,1990.3551193231879 1997.358735770496,1991.0557280900007 1995.5278640450006,1992.1000602103095 1993.8688539962527,1993.4479825863987 1992.445460450043,1995.0476953172788 1991.3123836221034,1996| SRID=3857;LINESTRING(1000 1000,1040 1020) |SRID=3857;LINESTRING(1200 1000,1140 1010,1160 1020)|SRID=3857;MULTIPOLYGON(((1990.0251579118735 1999.2911097990932,1990.3551193231879 1997.358735770496,1991.0557280900007 1995.5278640450006,1992.1000602103095 1993.8688539962527,1993.4479825863987 1992.445460450043,1995.0476953172788 1991.3123836221034,1996| SRID=3857;LINESTRING(1100 1000,1120 1010,1110 1020)|SRID=3857;LINESTRING(1200 1000,1140 1010,1160 1020)|SRID=3857;MULTIPOLYGON(((2190.0251579118735 1999.2911097990932,2190.355119323188 1997.358735770496,2191.055728090001 1995.5278640450006,2192.1000602103095 1993.8688539962527,2193.4479825863987 1992.445460450043,2195.0476953172792 1991.3123836221034,2196.8|

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