输入几何体具有未知(0)SRID

Question

在下面的文章中，我进行了一些查询，结果很好。然而，当我添加进行坐标转换的行和查询geom的行时，我在运行web服务时收到以下错误：

Input geometry has unknown (0) SRID

我是Postgis的新手。如何解决此问题？

代码：

query = """  WITH data AS (
SELECT '{featuresArray}'::json AS featuresCollection
)
SELECT gid,geom,type::text,properties::text,
array_to_string(array_agg(x_4326||' '||y_4326 ORDER BY gid),',') AS g4326,
array_to_string(array_agg(x_25832||' '||y_25832 ORDER BY gid),',') AS g25832             
FROM (
SELECT
ROW_NUMBER() OVER () AS gid,
ST_AsText(ST_GeomFromGeoJSON(feature->>'geometry')) AS geom,
feature->>'type' AS type,
feature->>'properties' AS properties,
ST_X((ST_DumpPoints((ST_GeomFromGeoJSON(feature->>'geometry')))).geom) x_4326,       
ST_Y((ST_DumpPoints((ST_GeomFromGeoJSON(feature->>'geometry')))).geom) y_4326,  
ST_X((ST_DumpPoints((ST_Transform(ST_GeomFromGeoJSON(feature->>'geometry'),25832)))).geom) x_25832,       
ST_X((ST_DumpPoints((ST_Transform(ST_GeomFromGeoJSON(feature->>'geometry'),25832)))).geom) y_25832
FROM (SELECT json_array_elements(featuresCollection->'features') AS feature FROM data) AS f) j
GROUP BY gid,type::text,properties::text,geom
ORDER BY gid;""".format(featuresArray=featuresArray)

Answer 1

一些PostGIS函数依赖于SRS，例如ST_Transform。您必须指定要从哪个SRS进行转换，否则转换脚本没有计算新坐标的参考，例如从EPSG:25832到EPSG:4326:

SELECT ST_Transform('SRID=25832;POINT(1 1)',4326);

否则将引发异常

SELECT ST_Transform('POINT(1 1)',4326); -- <-- WKT literal without SRS
ERROR:  ST_Transform: Input geometry has unknown (0) SRID

使用ST_SetSRID，您可以将SRS设置为几何图形，以防它们没有几何图形——正如您的示例所示，例如

SELECT ST_Transform(
ST_SetSRID('POINT(1 1)'::geometry,25832),
4326);

CREATE TABLE和INSERT/UPDATE语句也适用相同的原理。创建表时，我们声明SRS如下。。

CREATE TABLE t (geom geometry(point,4326));

因此PostGIS希望所有传入的几何图形都具有相同的SRS。。

INSERT INTO t VALUES ('SRID=4326;POINT(1 1)'); 

否则它也会引发异常

INSERT INTO t VALUES ('SRID=25832;POINT(1 1)'); 
ERROR:  Geometry SRID (25832) does not match column SRID (4326)