Geometry Functions - Revision history

Michaudm at 10:09, 6 May 2012

2012-05-06T10:09:24Z

Michaudm at 21:02, 13 April 2012

2012-04-13T21:02:38Z

Michaudm at 07:50, 9 July 2011

2011-07-09T07:50:10Z

Michaudm at 07:49, 9 July 2011

2011-07-09T07:49:17Z

Michaudm at 07:39, 9 July 2011

2011-07-09T07:39:48Z

Michaudm at 22:58, 8 July 2011

2011-07-08T22:58:21Z

Michaudm at 21:08, 8 July 2011

2011-07-08T21:08:16Z

Michaudm: Created page with ' File:GeometryFunctions.png'

2011-07-08T20:41:00Z

Created page with ' File:GeometryFunctions.png'

New page

[[File:GeometryFunctions.png]]

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 ** '''Simplify (D-P)''' - Simplify each geometry using the Douglas-Peucker algorithm. Ensures that any polygonal geometries returned are valid. Simple lines are not guaranteed to remain simple after simplification. Note that in general D-P does not preserve topology - e.g. polygons can be split, collapse to lines or disappear holes can be created or disappear, and lines can cross. To simplify geometry while preserving topology use TopologyPreservingSimplifier. (However, using D-P is significantly faster).
 ** '''Simplify (Preserve Topology)''' - Simplifies each geometry, ensuring that the result is a valid geometry having the same dimension and number of components as the input. The simplification uses a maximum distance difference algorithm similar to the one used in the Douglas-Peucker algorithm.
-** '''Densify''' - [New in OpenJUMP 1.6] Densify a geometry by adding a pont every xxx units.
+** '''Densify''' - <span style="color:red">'''[New in OpenJUMP 1.6]'''</span> Densify a geometry by adding a pont every xxx units.
 ** '''Concex Hull''' - Returns convex hull of each geometry. Convex hull dimension depends on the input geometry. Convex hull of a point is a point, convex hull of a straight line or a multipoint made of two points is a linestring, convex hull of a complex (multi)linestring or a (multi)polygon is a polygon.
 ** '''Boundary''' - Returns the boundary, or an empty geometry of appropriate dimension if the geometries are empty. (In the case of zero-dimensional geometries, ' an empty GeometryCollection is returned.) For a discussion of this function, see the OpenGIS Simple Features Specification. As stated in SFS Section 2.1.13.1, "the boundary of a Geometry is a set of Geometries of the next lower dimension."

@@ Line 26: / Line 26: @@
 ** '''Simplify (D-P)''' - Simplify each geometry using the Douglas-Peucker algorithm. Ensures that any polygonal geometries returned are valid. Simple lines are not guaranteed to remain simple after simplification. Note that in general D-P does not preserve topology - e.g. polygons can be split, collapse to lines or disappear holes can be created or disappear, and lines can cross. To simplify geometry while preserving topology use TopologyPreservingSimplifier. (However, using D-P is significantly faster).
 ** '''Simplify (Preserve Topology)''' - Simplifies each geometry, ensuring that the result is a valid geometry having the same dimension and number of components as the input. The simplification uses a maximum distance difference algorithm similar to the one used in the Douglas-Peucker algorithm.
 ** '''Concex Hull''' - Returns convex hull of each geometry. Convex hull dimension depends on the input geometry. Convex hull of a point is a point, convex hull of a straight line or a multipoint made of two points is a linestring, convex hull of a complex (multi)linestring or a (multi)polygon is a polygon.
 ** '''Boundary''' - Returns the boundary, or an empty geometry of appropriate dimension if the geometries are empty. (In the case of zero-dimensional geometries, ' an empty GeometryCollection is returned.) For a discussion of this function, see the OpenGIS Simple Features Specification. As stated in SFS Section 2.1.13.1, "the boundary of a Geometry is a set of Geometries of the next lower dimension."

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 ''Use Selected Features Only'' -  If checked, only selected features '''of the source layer''' will be processed. If not checked, each feature of the source layer will be processed.
 ''Create new layer for result'' - With this default option, result will be output in a new layer.
 ''Update Source features with the result'' - This option is useful to update a layer. Processed feature geometries will be replace source ones.
 ''Add Result to source layer'' - May be useful to add new features to a layer while keeping original ones.
 * '''Geometry functions using a layer and a mask''' - A mask is a layer containing a single geometry. The following functions will compare each geometry of the source layer to the mask. Note that the single geometry contained in the mask may be a MultiGeometry but not a GeometryCollection. The result contains as many features as the source layer.

@@ Line 3: / Line 3: @@
 [[File:GeometryFunctions.png]]
-Geometry Functions is a very rich tool. How it works depends highly on the geometry function you choose :
+Geometry Functions is a very complete tool for geometry processing. How it works depends on the geometry function you choose and on the following options :
 * '''Geometry functions using a layer and a mask''' - A mask is a layer containing a single geometry. The following functions will compare each geometry of the source layer to the mask. Note that the single geometry contained in the mask may be a MultiGeometry but not a GeometryCollection. The result contains as many features as the source layer.
-** ''Intersections'' - Creates features which are the intersection of source feature geometries with the mask.
+** '''Intersections''' - Creates features which are the intersection of source feature geometries with the mask.
-** ''Union'' - Creates features which are the union of each single feature of source layer with the feature geometry of mask.
+** '''Union''' - Creates features which are the union of each single feature of source layer with the feature geometry of mask.
-** ''Difference (A-B)'' - Substract geometry of the mask to each feature of the source layer. You can for example clean a layer by removing parts of feature geometries overlapping the ocean surface..
+** '''Difference (A-B)''' - Substract geometry of the mask to each feature of the source layer. You can for example clean a layer by removing parts of feature geometries overlapping the ocean surface..
-** ''Difference (B-A)'' - You may want  to do the opposite : remove feature geometries from ocean area.
+** '''Difference (B-A)''' - You may want  to do the opposite : remove feature geometries from ocean area.
-** ''Symmetric difference'' - Symmetric difference will keep the part of source geometries which does not intersect the mask with the part of the mask which does not intersects the source geometry.
+** '''Symmetric difference''' - Symmetric difference will keep the part of source geometries which does not intersect the mask with the part of the mask which does not intersects the source geometry.
 * '''Geometry functions using a single layer'''
-** ''Centroid of A'' - Computes the centroid of each feature geometry. The centroid is equal to the centroid of the set of component Geometries of highest dimension (since the lower-dimension geometries contribute zero "weight" to the centroid).
+** '''Centroid of A''' - Computes the centroid of each feature geometry. The centroid is equal to the centroid of the set of component Geometries of highest dimension (since the lower-dimension geometries contribute zero "weight" to the centroid).
-** ''Interior Point'' - Computes an interior for each feature Geometry. An interior point is guaranteed to lie in the interior of the Geometry, if it possible to calculate such a point exactly. Otherwise, the point may lie on the boundary of the geometry.
+** '''Interior Point''' - Computes an interior for each feature Geometry. An interior point is guaranteed to lie in the interior of the Geometry, if it possible to calculate such a point exactly. Otherwise, the point may lie on the boundary of the geometry.
-** ''Buffer'' - Computes a buffer for each geometry. Just take a distance paramater. If you need more options, use Analysis > Buffer... tool.
+** '''Buffer''' - Computes a buffer for each geometry. Just take a distance paramater. If you need more options, use Analysis > Buffer... tool.
-** ''Simplify (D-P)'' - Simplify each geometry using the Douglas-Peucker algorithm. Ensures that any polygonal geometries returned are valid. Simple lines are not guaranteed to remain simple after simplification. Note that in general D-P does not preserve topology - e.g. polygons can be split, collapse to lines or disappear holes can be created or disappear, and lines can cross. To simplify geometry while preserving topology use TopologyPreservingSimplifier. (However, using D-P is significantly faster).
+** '''Simplify (D-P)''' - Simplify each geometry using the Douglas-Peucker algorithm. Ensures that any polygonal geometries returned are valid. Simple lines are not guaranteed to remain simple after simplification. Note that in general D-P does not preserve topology - e.g. polygons can be split, collapse to lines or disappear holes can be created or disappear, and lines can cross. To simplify geometry while preserving topology use TopologyPreservingSimplifier. (However, using D-P is significantly faster).
-** ''Simplify (Preserve Topology)'' - Simplifies each geometry, ensuring that the result is a valid geometry having the same dimension and number of components as the input. The simplification uses a maximum distance difference algorithm similar to the one used in the Douglas-Peucker algorithm.
+** '''Simplify (Preserve Topology)''' - Simplifies each geometry, ensuring that the result is a valid geometry having the same dimension and number of components as the input. The simplification uses a maximum distance difference algorithm similar to the one used in the Douglas-Peucker algorithm.
-** ''Concex Hull'' - Returns convex hull of each geometry. Convex hull dimension depends on the input geometry. Convex hull of a point is a point, convex hull of a straight line or a multipoint made of two points is a linestring, convex hull of a complex (multi)linestring or a (multi)polygon is a polygon.
+** '''Concex Hull''' - Returns convex hull of each geometry. Convex hull dimension depends on the input geometry. Convex hull of a point is a point, convex hull of a straight line or a multipoint made of two points is a linestring, convex hull of a complex (multi)linestring or a (multi)polygon is a polygon.
-** ''Boundary'' - Returns the boundary, or an empty geometry of appropriate dimension if the geometries are empty. (In the case of zero-dimensional geometries, ' an empty GeometryCollection is returned.) For a discussion of this function, see the OpenGIS Simple Features Specification. As stated in SFS Section 2.1.13.1, "the boundary of a Geometry is a set of Geometries of the next lower dimension."
+** '''Boundary''' - Returns the boundary, or an empty geometry of appropriate dimension if the geometries are empty. (In the case of zero-dimensional geometries, ' an empty GeometryCollection is returned.) For a discussion of this function, see the OpenGIS Simple Features Specification. As stated in SFS Section 2.1.13.1, "the boundary of a Geometry is a set of Geometries of the next lower dimension."
-** ''Envelope'' - Returns rectangular envelope of each geometry. Envelope can be a point (for point geometry) or a linestring (ex. horizontal linestring).
+** '''Envelope''' - Returns rectangular envelope of each geometry. Envelope can be a point (for point geometry) or a linestring (ex. horizontal linestring).
-** ''Reverse Line Direction'' - Reverse the orientation of each linear element. Polygon boundaries are also reversed. '''Warning''' : lines are reversed on the new layer '''AND on the source layer''', which must be considered as a bug.
+** '''Reverse Line Direction''' - Reverse the orientation of each linear element. Polygon boundaries are also reversed. '''Warning''' : lines are reversed on the new layer '''AND on the source layer''', which must be considered as a bug.
 * '''Geometry functions usually working on a set of geometries)''' - Following functions are also applied to each geometry of the source layer. To make them useful, you'll probably have to combine input features into a single multi-geometry first, then explode the result.
-** ''Line Merge'' - Merge contiguous lines of a multilinestring. Linestring are not merged if the order of their common node is 3 or more (A-B and B-C are merged, but A-B, B-C and B-D are not merged).
+** '''Line Merge''' - Merge contiguous lines of a multilinestring. Linestring are not merged if the order of their common node is 3 or more (A-B and B-C are merged, but A-B, B-C and B-D are not merged).
-** ''Line Sequence'' - Lines of the multilinestring are not merged, but they are oriented so that the end of a line equals the start of the following one, while preserving the original orientation as much as possible. For a complete description, see the [http://tsusiatsoftware.net/jts/javadoc/com/vividsolutions/jts/operation/linemerge/LineSequencer.html javadoc].
+** '''Line Sequence''' - Lines of the multilinestring are not merged, but they are oriented so that the end of a line equals the start of the following one, while preserving the original orientation as much as possible. For a complete description, see the [http://tsusiatsoftware.net/jts/javadoc/com/vividsolutions/jts/operation/linemerge/LineSequencer.html javadoc].
-** ''Polygonize'' - Build polygons from a set of '''noded''' linestrings. Noded means that there should be a node at each intersection, not only a vertex. To achieve that, you may have to compute intersections first. Note that there is a more complete Polygonizer in the Edit Geometry menu.
+** '''Polygonize''' - Build polygons from a set of '''noded''' linestrings. Noded means that there should be a node at each intersection, not only a vertex. To achieve that, you may have to compute intersections first. Note that there is a more complete Polygonizer in the Edit Geometry menu.

@@ Line 13: / Line 13: @@
 * '''Geometry functions using a single layer'''
 ** ''Centroid of A'' - Computes the centroid of each feature geometry. The centroid is equal to the centroid of the set of component Geometries of highest dimension (since the lower-dimension geometries contribute zero "weight" to the centroid).
-** ''Interior Point''
+** ''Interior Point'' - Computes an interior for each feature Geometry. An interior point is guaranteed to lie in the interior of the Geometry, if it possible to calculate such a point exactly. Otherwise, the point may lie on the boundary of the geometry.
-** ''Buffer''
+** ''Buffer'' - Computes a buffer for each geometry. Just take a distance paramater. If you need more options, use Analysis > Buffer... tool.
-** ''Simplify (D-P)''
+** ''Simplify (D-P)'' - Simplify each geometry using the Douglas-Peucker algorithm. Ensures that any polygonal geometries returned are valid. Simple lines are not guaranteed to remain simple after simplification. Note that in general D-P does not preserve topology - e.g. polygons can be split, collapse to lines or disappear holes can be created or disappear, and lines can cross. To simplify geometry while preserving topology use TopologyPreservingSimplifier. (However, using D-P is significantly faster).
-** ''Simplify (Preserve Topology)''
+** ''Simplify (Preserve Topology)'' - Simplifies each geometry, ensuring that the result is a valid geometry having the same dimension and number of components as the input. The simplification uses a maximum distance difference algorithm similar to the one used in the Douglas-Peucker algorithm.

← Older revision		Revision as of 21:08, 8 July 2011
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		+	[[Tools]]

		+	[[File:GeometryFunctions.png]]

−	~~[[File~~:~~GeometryFunctions~~.~~png]]~~	+	Geometry Functions is a very rich tool. How it works depends highly on the geometry function you choose :
		+
		+	* '''Geometry functions using a mask''' - A mask is a layer containing a single geometry. The following functions will compare each geometry of the source layer to the mask. Note that the single geometry contained in the mask may be a MultiGeometry but not a GeometryCollection. The result contains as many features as the source layer.
		+	** ''Intersections'' - Creates features which are the intersection of source feature geometries with the mask.
		+	** ''Union'' - Creates features which are the union of each single feature of source layer with the feature geometry of mask.
		+	** ''Difference (A-B)'' - Substract geometry of the mask to each feature of the source layer. You can for example clean a layer by removing parts of feature geometries overlapping the ocean surface..
		+	** ''Difference (B-A)'' - You may want to do the opposite : remove feature geometries from ocean area.
		+	** ''Symmetric difference'' - Symmetric difference will keep the part of source geometries which does not intersect the mask with the part of the mask which does not intersects the source geometry.