错误空间子集和PostGIS数据库

Question

我正在尝试使用sqlalchemy和geoalchemy2在Python 3.5上进行空间操作.我有一个点作为geom属性的表.我已阅读该表并按照文档说明操作:

metadata = MetaData()
table = Table('table', 
                 metadata, autoload=True,
                 schema = "schema",
                 autoload_with=engine)
print(table.columns)

这正确地返回了我的表的列的名称.现在,我想创建数据的空间子集,仅选择POLYGON对象内的点.我尝试过ST_Contains和ST_Intersection:

# Create session for queries
Session = sessionmaker(bind=engine)
session = Session()

#SELECT * FROM table:
q = session.query(table).filter(table.c.geom.ST_Intersects(func.GeomFromEWKT(<POLYGON>)))

POLYGON是具有定义的WKT几何SRID=4326.我已经尝试过使用相同多边形的不同形式,但没有一个有效.执行查询时,以下错误返回:

(psycopg2.InternalError) geometry contains non-closed rings
HINT:  "...140.965576171875 -11.11288507032144))" <-- parse error at position 166 within geometry

我失败的地方？

Answer 1

您使用的多边形未闭合。第一个和最后一个坐标必须相同。将其更改为：

wkt_string = "POLYGON((141.0205078125 -9.166331387642987, 
                       143.602294921875 -9.155485188844034, 
                       143.67919921875 -11.112885070321443, 
                       140.965576171875 -11.11288507032144, 
                       141.0205078125 -9.166331387642987))"

或者，您可以从一条线构建多边形并自动添加缺失的点

SELECT ST_MakePolygon(
         ST_AddPoint(foo.open_line, ST_StartPoint(foo.open_line)))
FROM (
  SELECT ST_GeomFromText(
            'LINESTRING(141.0205078125 -9.166331387642987, 
                        143.602294921875 -9.155485188844034,
                        143.67919921875 -11.112885070321443, 
                        140.965576171875 -11.11288507032144)')
              As open_line) 
   As foo;