ST_Within 不 return 正确

Question

我使用 ogr2ogr 工具从 GeoPackage 导入了一些数据。我假设导入操作没有任何故障，因为导入的多边形（geom 列）ST_IsValidReason() returns Valid Geometry。

nzstat=# \d sa2_2020
                                           Table "public.sa2_2020"
     Column      |            Type             | Collation | Nullable |                Default                
-----------------+-----------------------------+-----------+----------+---------------------------------------
 gid             | integer                     |           | not null | nextval('sa2_2020_gid_seq'::regclass)
 sa22018_v1_00   | character varying           |           |          | 
 sa22018_v1_name | character varying           |           |          | 
 land_area_sq_km | double precision            |           |          | 
 area_sq_km      | double precision            |           |          | 
 shape_length    | double precision            |           |          | 
 geom            | geometry(MultiPolygon,2193) |           |          | 
Indexes:
    "sa2_2020_pkey" PRIMARY KEY, btree (gid)
    "sa2_2020_geom_geom_idx" gist (geom)

nzstat=# select ST_IsValidReason(geom) from sa2_2020 where gid=4;
 st_isvalidreason 
------------------
 Valid Geometry
(1 row)

nzstat=# select ST_IsValidReason(ST_SetSRID(ST_MakePoint(174.77632, -41.28671), 2193));
 st_isvalidreason 
------------------
 Valid Geometry
(1 row)

nzstat=# select sa22018_v1_name from sa2_2020 where ST_Within(ST_SetSRID(ST_MakePoint(174.82726, -41.16671), 2193), geom);
 sa22018_v1_name 
-----------------
(0 rows)

nzstat=#

我用于 ST_MakePoint() 的坐标来自另一个数据库，该数据库在 NZGD2000 坐标系 (SRID = 2193)

中提供 x 和 y 值

               full_address_ascii                | gd2000_xcoord | gd2000_ycoord        
-------------------------------------------------+---------------+---------------
 1 Willis Street, Wellington Central, Wellington |     174.77632 |     -41.28671

坐标应位于多个多边形之一，但我的查询 returns 没有结果。我在这里遗漏了什么吗？

我使用 PostGIS 3.2 和 PostgeSQL 13.5。

谢谢

Answer 1

EPSG:2193 的坐标以米为单位，因此您的值 (174.82726, -41.16671) 不太可能在该投影中，它们更有可能以度为单位 (WGS84, EPGS:4326 ).所以你需要转换你的点以将它们与 EPSG:2193 中的多边形进行比较，因此你的 SQL 应该是这样的：

select sa22018_v1_name from sa2_2020 where ST_Within(ST_TRANSFORM(ST_MakePoint(174.82726, -41.16671), 2193), geom);

ST_SetSRID only changes the metadata of the point (setting the CRS), to actually change the values of a point's coordinates you need to reproject the point (transform it from one projection to another) and so must use ST_Transform.

ST_Within 不 return 正确

ST_Within does not return true

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