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60 changes: 35 additions & 25 deletions docs/user_manual/processing_algs/algs_include.rst
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Expand Up @@ -162,46 +162,56 @@ comparing them to the orange rectangle feature.
Available geometric predicates are:

*Intersect*
Tests whether a geometry intersects another. Returns 1 (true) if the
geometries spatially intersect (share any portion of space - overlap or touch) and 0 if they
don’t. In the picture above, this will return circles 1, 2 and 3.
Tests whether a geometry intersects another.
Returns 1 (true) if the input layer geometry and the join layer geometry spatially intersect
(share any portion of space - overlap or touch) and 0 if they don't. In the figure above,
if the rectangle is the input layer and circles are the join layer, this will return circles 1, 2 and 3.

*Contain*
Returns 1 (true) if and only if no points of b lie in the exterior of a,
and at least one point of the interior of b lies in the interior of a.
In the picture, no circle is returned, but the rectangle would be if you
would look for it the other way around, as it contains circle 1 completely.
This is the opposite of *are within*.
Returns 1 (true) if and only if no points of the join layer geometry lie in the exterior
of the input layer geometry, and at least one point of the interior of the join layer geometry
lies in the interior of the input layer geometry.
In other words, the input layer feature must completely contain the join layer feature.
In the figure, if the rectangle is the input layer and circles are the join layer,
circle 1 is returned, as the rectangle contains it completely. This is the opposite of *are within*.

*Disjoint*
Returns 1 (true) if the geometries do not share any portion of space (no overlap, not touching).
Only circle 4 is returned.
Returns 1 (true) if the input layer geometry and the join layer geometry
do not share any portion of space (no overlap, not touching).
In the figure, if the rectangle is the input layer and circles are the join layer,
only circle 4 is returned.

*Equal*
Returns 1 (true) if and only if geometries are exactly the same.
No circles will be returned.
Returns 1 (true) if and only if the input layer geometry and the join layer geometry
are exactly the same. In the figure, if the rectangle is the input layer and circles are the join layer,
no circles will be returned.

*Touch*
Tests whether a geometry touches another. Returns 1 (true) if the geometries
Tests whether a geometry touches another.
Returns 1 (true) if the input layer geometry and the join layer geometry
have at least one point in common, but their interiors do not intersect.
Only circle 3 is returned.
In the picture, if the rectangle is the input layer and circles are the join layer,
only circle 3 is returned.

*Overlap*
Tests whether a geometry overlaps another. Returns 1 (true) if the geometries
share space, are of the same dimension, but are not completely contained by
each other. Only circle 2 is returned.
Tests whether a geometry overlaps another.
Returns 1 (true) if the input layer geometry and the join layer geometry share space,
are of the same dimension, but are not completely contained by each other.
In the figure, if the rectangle is the input layer and circles are the join layer,
only circle 2 is returned.

*Are within*
Tests whether a geometry is within another. Returns 1 (true) if geometry a
is completely inside geometry b. Only circle 1 is returned.
Tests whether a geometry is within another.
Returns 1 (true) if the input layer geometry is completely inside the join layer geometry.
In the figure, if the circles are the input layer and the rectangle is the join layer,
only circle 1 is returned. This is the opposite of *contain*.

*Cross*
Returns 1 (true) if the supplied geometries have some, but not all, interior
points in common and the actual crossing is of a lower dimension than the
highest supplied geometry. For example, a line crossing a polygon will cross
as a line (true). Two lines crossing will cross as a point (true).
Two polygons cross as a polygon (false).
In the picture, no circles will be returned.
Returns 1 (true) if the supplied geometries have some,
but not all, interior points in common and the actual crossing is of a lower dimension
than the highest supplied geometry. For example, a line crossing a polygon will cross as a line (true).
Two lines crossing will cross as a point (true). Two polygons cross as a polygon (false).
In the figure, if the rectangle is the input layer and circles are the join layer, no circles will be returned.

.. **end_geometric_predicates**

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