geo:region-relate( $region-1 as cts:region, $operation as xs:string, $region-2 as cts:region, [$options as xs:string*] ) as xs:boolean
Compares geospatial regions based on a specified relationship. For example, determine if two regions overlap.
This function determines whether the two regions
R1=$region-1
and R2=$region-2
satisfy the relationship R1 op R2, where
op=$operation
.
The operations are defined by the Dimensionally Extended nine-Intersection Model (DE-9IM) of spatial relations. They have the following semantics:
"contains"
- R1 contains R2 if every point of R2 is also a point of R1, and their interiors intersect.
"covered-by"
- R1 is covered-by R2 if every point of R1 is also a point of R2.
"covers"
- R1 covers R2 if every point of R2 is also a point of R1.
"crosses"
- R1 crosses R2 if their interiors intersect and the dimension of the intersection is less than that of at least one of the regions.
"disjoint"
- R1 is disjoint from R2 if they have no points in common.
"equals"
- R1 equals R2 if every point of R1 is a point of R2, and every point of R2 is a point of R1. That is, the regions are topologically equal.
"intersects"
- R1 intersects R2 if the two regions have at least one point in common.
"overlaps"
- R1 overlaps R2 if the two regions partially intersect -- that is, they have some but not all points in common -- and the intersection of R1 and R2 has the same dimension as R1 and R2.
"touches"
- R1 touches R2 if they have a boundary point in common but no interior points in common.
"within"
- R1 is within R2 if every point of R1 is also a point of R2, and their interiors intersect.
The operations in this function are the same as those used
in cts:geospatial-region-query,
with identical semantics. For example,
geo:region-relate($r1,$op,$r2)
returns true if and only if a document containing the region
$r1
would match the geospatial region query
cts:geospatial-region-query($index,$op,$r2)
.
(Where $index
is a geospatial region path index configured on
the same coordinate system and units used in
geo:region-relate
.)
Note: the operation covers
differs from contains
only in that covers
does not distinguish between points in the
boundary and the interior of geometries. In general, covers
should be used in preference to contains
. Similarly,
covered-by
should generally be used in preference to
within
.
The DE9-IM operators are defined in terms of the underlying intersection matrix between the two regions. To calculate this matrix for two regions, use geo:region-de9im.
The value of the precision
option takes precedence over
that implied by the governing coordinate system name, including the
value of the coordinate-system
option. For example, if the
governing coordinate system is "wgs84/double" and the precision
option is "float", then the operation uses single precision.
let $r1 := cts:polygon("POLYGON((-122.427520751953 37.6555576956251,-122.459106445313 37.5658069549294,-122.289505004883 37.5946477878735,-122.427520751953 37.6555576956251))") let $r2 := cts:linestring("LINESTRING(-122.571029663086 37.5728821555562,-122.400054931641 37.6077041124284,-122.161102294922 37.5696167618573)") return geo:region-relate($r1,"crosses",$r2,("coordinate-system=wgs84","precision=double")) (: returns true :)
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