MarkLogic Server 11.0 Product Documentation

geo:region-relate

geo:region-relate(
   $region-1 as cts:region,
   $operation as xs:string,
   $region-2 as cts:region,
   [$options as xs:string*]
) as xs:boolean

Summary

Compares geospatial regions based on a specified relationship. For example, determine if two regions overlap.

Usage Notes

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.

See Also

• Geospatial Region Queries and Indexes in the Search Developer's Guide
• Searching for Matching Regions in the Search Developer's Guide

Example

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 :)