st_intersects与st_overlaps

Question

这两个查询有什么区别：

select a.gid, sum(length(b.the_geom)) 
  from polygons as a 
     , roads as b 
 where st_intersects(a.the_geom,b.the_geom) 
 group by a.gid ;

select a.gid, sum(length(b.the_geom)) 
  from polygons as a 
     , roads as b 
 where st_overlaps(a.the_geom,b.the_geom) 
 group by a.gid ;

第一个查询给出正确的输出，而第二个查询根本不检索任何行。与多边形相交的道路也重叠了，对吗？

Answer 1

从PostGIS的文档中

http://postgis.net/docs/ST_Intersects.html

如果几何或地理共享空间的任何部分，则它们相交。重叠，触摸，所有暗示空间相交。如果上述任何一项返回true，则几何形状也会在空间上相交。

http://postgis.net/docs/ST_Overlaps.html

如果几何“空间重叠”，则返回TRUE。我们的意思是它们相交，但是一个并不完全包含另一个。

区别是：如果两个几何重叠100％，则它们不再重叠。

这是一个POSTGIS示例：

SELECT ST_Overlaps(a,b) As a_overlap_b, ST_Intersects(a, b) As a_intersects_b, ST_Contains(b, a) As b_contains_a
FROM (SELECT 
    ST_Polygon(ST_GeomFromText('LINESTRING(1 1,3 1,3 3,1 1)'), 4326)  As a,
    ST_Polygon(ST_GeomFromText('LINESTRING(1 1,3 1,3 3,1 1)'), 4326)  As b)
    As foo;
    -- INTERSECT is TRUE, OVERLAP is FALSE because B equals A

    SELECT ST_Overlaps(a,b) As a_overlap_b, ST_Intersects(a, b) As a_intersects_b, ST_Contains(b, a) As b_contains_a
FROM (SELECT 
    ST_Polygon(ST_GeomFromText('LINESTRING(1 1,3 1,3 3,1 1)'), 4326)  As a,
    ST_Polygon(ST_GeomFromText('LINESTRING(1 1,4 1,4 4,1 1)'), 4326)  As b)
    As foo;
    -- INTERSECT is TRUE, OVERLAP is FALSE because B contains A

    SELECT ST_Overlaps(a,b) As a_overlap_b, ST_Intersects(a, b) As a_intersects_b, ST_Contains(b, a) As b_contains_a
FROM (SELECT 
    ST_Polygon(ST_GeomFromText('LINESTRING(0 0,2 0,2 2,0 0)'), 4326)  As a,
    ST_Polygon(ST_GeomFromText('LINESTRING(1 1,3 1,3 3,1 1)'), 4326)  As b)
    As foo;
    -- INTERSECT is TRUE, OVERLAP is TRUE because not all of A intersects B and not all of B intersects A