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network_advanced_parameters

Direction field [tablefield: string]

Optional

The field used to specify directions for the network edges.

The values used in this field are specified with the three parameters Value for forward direction, Value for backward direction and Value for both directions. Forward and reverse directions correspond to a one-way edge, “both directions” indicates a two-way edge.

If a feature does not have a value in this field, or no field is set then the default direction setting (provided with the Default direction parameter) is used.

Value for forward direction [string]

Optional

Value set in the direction field to identify edges with a forward direction.

Value for backward direction [string]

Optional

Value set in the direction field to identify edges with a backward direction.

Value for both directions [string]

Optional

Value set in the direction field to identify bidirectional edges.

Default direction [enumeration]

If a feature has no value set in the direction field or if no direction field is set, then this direction value is used.

Available options are:

0 — Forward direction
1 — Backward direction
2 — Both directions

Default: 2

Speed field [tablefield: string]

Optional

Field providing the speed value (in km/h) for the edges of the network when looking for the fastest path.

If a feature does not have a value in this field, or no field is set then the default speed value (provided with the Default speed parameter) is used.

Default speed (km/h) [number]

Value to use to calculate the travel time if no speed field is provided for an edge.

Default: 50.0

Topology tolerance [number]

Two lines with nodes closer than the specified tolerance are considered connected.

Default: 0.0

end_network_advanced_parameters

geometric_predicates

../../../../_images/selectbylocation.png

In this example, the dataset from which we want to select (the source vector layer) consists of the green circles, the orange rectangle is the dataset that it is being compared to (the intersection vector layer).¶

Where the features (geometric predicate) [enumeration] [list]

The spatial condition for the selection is defined by choosing one or more geometric predicates.

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 select 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 selected, but the rectangle would be if you would select it the other way around, as it contains a circle 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 selected.
Equal: Returns 1 (true) if and only if geometries are exactly the same. No circles will be selected.
Touch: Tests whether a geometry touches another. Returns 1 (true) if the geometries have at least one point in common, but their interiors do not intersect. Only circle 3 is selected.
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 selected.
Are within: Tests whether a geometry is within another. Returns 1 (true) if geometry a is completely inside geometry b. Only circle 1 is selected.
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 (selected). Two lines crossing will cross as a point (selected). Two polygons cross as a polygon (not selected).

Default: Intersect

end_geometric_predicates

postgisexecutesqlexample

Example

For all features / rows in a PostGIS / PostgreSQL table (“your_table”), set the value of an existing field (“field_to_update”) to a given value (20). The SQL query string:
```
UPDATE your_table SET field_to_update=20;
```

Create a new area column and calculate the area of each feature: with the ST_AREA PostGIS function.

-- Create the new column "area" in a table named "your_table"
ALTER TABLE your_table ADD COLUMN area double precision;
-- Update the "area" column of each feature with the its area:
UPDATE your_table SET area=ST_AREA(geom);

end_postgisexecutesqlexample