GeometryEqual (Function)

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Accessing spatial data: using spatial indexes

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GeometryEqual (Function)

In french: GéométrieEgale

Determines whether two geometries are spatially equal, i.e. whether the first geometry is included in the second, and vice versa.

Remarks:

Two geometries can be spatially equal without having the same content: they must simply occupy the same space.
Geometry types must be the same (otherwise geometries will never be equal), with the exception of polygons and multipolygons, which can describe the same surface.

Example

// Define the same square twice, but with points in different order
o2DPolygon_1 is Polygon2D
Linestring2DAddPoint(o2DPolygon_1.Outline, -1.00, 1.00)
Linestring2DAddPoint(o2DPolygon_1.Outline, 1.00, 1.00)
Linestring2DAddPoint(o2DPolygon_1.Outline, 1.00, -1.00)
Linestring2DAddPoint(o2DPolygon_1.Outline, -1.00, -1.00)
// Add last point (same as first)
Linestring2DAddPoint(o2DPolygon_1.Outline, 1.00, 1.00)

o2DPolygon_2 is Polygon2D
Linestring2DAddPoint(o2DPolygon_2.Outline, 1.00, -1.00)
Linestring2DAddPoint(o2DPolygon_2.Outline, -1.00, -1.00)
Linestring2DAddPoint(o2DPolygon_2.Outline, -1.00, 1.00)
Linestring2DAddPoint(o2DPolygon_2.Outline, 1.00, 1.00)
// Add last point (same as first)
Linestring2DAddPoint(o2DPolygon_2.Outline, 1.00, -1.00)

Trace(GeometryEqual(o2DPolygon_1, o2DPolygon_2)) // True

Syntax

<Result> = GeometryEqual(<Geometry A> , <Geometry B>)

<Result>: Boolean

True if geometry A and geometry B are spatially equal.
False otherwise.
If an error occurs, the ErrorOccurred variable is set to True. To get more details on the error, use ErrorInfo with the errMessage constant.

<Geometry A>: Variable containing spatial data

Variable corresponding to the first geometry. This geometry can correspond to one of the following variable types:
PointGeo.
Point2D.
LinestringGeo.
Linestring2D.
PolygonGeo.
Polygon2D.
MultiPointGeo.
MultiPoint2D.
MultiLinestringGeo.
MultiLinestring2D.
MultiPolygonGeo.
MultiPolygon2D.

<Geometry B>: Variable containing spatial data

Variable corresponding to the second geometry. This geometry can correspond to one of the following variable types:
PointGeo.
Point2D.
LinestringGeo.
Linestring2D.
PolygonGeo.
Polygon2D.
MultiPointGeo.
MultiPoint2D.
MultiLinestringGeo.
MultiLinestring2D.
MultiPolygonGeo.
MultiPolygon2D.

Remarks

Accessing spatial data: using spatial indexes

In a data file, you can apply a filter on spatial data and loop through the file. For example, the filter can be based on the result of GeometryEqual.

It is recommended to use the following syntax to apply a filter on spatial data:

FOR EACH File WHERE WLanguage_function(File.Spatial_item, Spatial_variable)

where:

WLanguage_function corresponds to GeometryEqual.
Spatial_item is a spatial item in the data file. This item must:
- be of type "Geographic data" or "Geometric data".
- be defined as a "Spatial key".
Spatial_variable is a given spatial variable, used for comparison with the spatial item. This variable can be of type PolygonGeo, Polygon2D, etc.

Remark: The "FOR EACH File" syntax is available but not recommended, as it doesn't use spatial indexes and is therefore not optimized. In this case, the entire data file is looped through: spatial indexes are not used.

FOR EACH File
IF WLanguage_function(File.Spatial_item, Spatial_variable) = True THEN
...
END
END

Example:

// Define a triangle delimiting a geographic area
// Store this triangle in a variable of type PolygonGeo 
polyGeo is PolygonGeo
polyGeo.Outline.AddPoint(0n48.8187479172765, 0n1.9550104465229536)
polyGeo.Outline.AddPoint(0n48.685649220185574, 0n2.023674998054354)
polyGeo.Outline.AddPoint(0n48.82612543243871, 0n2.2106580854197566)
polyGeo = GeometryCorrect(polyGeo)

// Search for municipalities with territory within the specified triangle
NumberOfRecords is int
FOR EACH MunicipalityData where GeometryEqual(MunicipalityData.geometry, polyGeo) 
	// Name of municipality in a trace window
	Trace(MunicipalityData.MunicipalityName)
END

Business / UI classification: Business Logic

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