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ILWIS 3.7 now has the following vector applications:

PolygonMapBuffer
PolygonMapConvexHull
PolygonMapIntersect
PolygonMapDifference
PolygonMapSymetricDifference
PolygonMapRelate
PolygonMapUnion
SegmentMapVoronoi
SegmentMapTIN
SegmentMapDifference
SegmentMapSymetricDifference
SegmentMapUnion
SegmentMapIntersect
SegmentMapRelate
PointMapIntersect
PointMapDifference
PointMapSymetricDifference
PointMapUnion
PointMapRelation
PointMapPointInSegment

New Polygon Applications

PolygonMapBuffer

The buffer of a Point/Segment/Polygon at a distance r is the Polygon or MultiPolygon which contains all points within a distance d of the feature.


Syntax
PolygonMapBuffer(InputMap, BufferDistance,EndCapStyle);

The operation has three parameters:

Input map
Any polygon/point or segment map
Buffer distance
The distance of the points included. Positive and negative values are supported (dilation & erosion)
End cap style How the ends of lines are calculated

PolygonMapConvexHull

The convex hull of a Point/Segment/Polygon is the smallest convex Polygon that contains all the points in the Point/Segment/Polygon (collection).

Syntax
PolygonMapConvexHull(InputMap, isCombined)

Input map Any polygon/point or segment map
isCombined
Either create the convexhull over all the features or treat every element separately (which, in some case, might not make sense )



PolygonMapDifference

Calculates the difference between polygons in the two inputmaps. From Each polygon in the first input map the covering polygon(s) from the second input map, if any, is substracted.

(grey and orange lines are the boundaries of the original 2 polygons)

Syntax
PolygonMapDifference(Inputmap1, Inputmap2)

Inputmap1
PolygonMap
Inputmap2
PolygonMap

PolygonMapSymetricDifference

Calculates the symmetric difference between polygons in the two inputmaps. From Each polygon in the first input map the symmetric difference with any of the polygons from the secondmap is calculated

Syntax
PolygonMapSymetricDifference(Inputmap1, Inputmap2)

Inputmap1
PolygonMap
Inputmap2
PolygonMap

PolygonMapIntersect

Calculate the intersection of a polygon of the input map with polygons of the output map. The map will be associated with an attribute table that contains the values of the original maps in a certain polygon.


(grey and orange lines are the boundaries of the original 2 polygons)

Syntax
PolygonMapIntersect((Inputmap1, Inputmap2)

Inputmap1
PolygonMap
Inputmap2
PolygonMa

PolygonMapRelate

For each polygon in the first inputmap a Boolean test is done to each feature in the second output map to see if it holds true. If so, the polygon is included in the output map.

The following relations are implemented

Contains
returns true if this polygon contains the specified feature (excluding boundary).
CoveredBy
returns true if this polygon is covered by the specified feature.
Crosses returns true if this polygon crosses the specified feature. The features have some but not all interior points in common.
Disjoint returns true if this polygon is disjoint to the specified feature. The two features have no point in common.
Equals returns true if this polygon is equal to the specified feature. The two features have at least one point in common and no point of either feature lies in the exterior of the other feature.
Intersects returns true if this polygon intersects the specified feature. The two features have at least one point in common (intersect is the reverse of disjoint).
Overlaps

returns true if this polygon overlaps the specified feature. The features have some, but not all points in common. They have the same dimension and the intersection of the interiors of the two features has the same dimension as the features themselves.

Touches returns true if this polygon touches the specified geometry. The features have at least one point in common, but their interiors do not intersect.
Within returns true if this polygon is within the specified feature. Every point of this polygon is a point of the other feature and the interiors of the two features have at least one point in common.

Example for “contains”; only polygons that contain the pointmap (yellow dots) are shown.

Syntax
PolygonMapRelate(inputmap1, Inputmap2, relation, negation)

Inputmap1
PolygonMap
Inputmap2 Polygon/Segment or Pointmap
Relation See table above
Negation The relation can be negated to give the opposite result(“true”,”false”)

PolygonMapUnion

Merges polygons of the first input map with polygons of the second input map

New Segmentmap Applications

The set operations for segments are identical for segmentmaps: SegmentMapIntersect, SegmentMapDifference, SegmentMapSymetricDifference, SegmentMapUnion, SegmentMapRelate. The only difference is that the set operations for segmentmaps can use a polygonmap (if it is not a segmentmap) as second inputmap. In such a case, the operation works on the boundaries of the polygonmap.

SegmentMapVoronoi

From a pointmap, it creates the segmentmap that forms the Voronoi map in which all points on the segments have equal distance to the closest points. Note that the “areas” are not closed, because the boundary segment at the edge of the map would, in theory, go on forever.



Syntax
PolygonMapRelate(Input Pointmap, minimal distance)

Input pointmap
The input map used to calculate the voronoi boundaries.
Minimal distance The smallest distance which is used to calculate the boundaries. Points with a distance smaller than the minimum are not used in the calculation in relation to each other.



SegmentMapTIN

Creates an irregular triangulated network from a input pointmap. This is a ‘bare bones’ implementation of a TIN and only deals with the creation of the segment map. Optionally it can choose to use conves hulls for elements at the edge of the TIN to create a better area filling.



Syntax
SegmentMapTIN(Input pointmap, use Convex hull)

Input pointmap
The input map used to calculate the TIN
Use convex hull “True” or “False”. Determines if the TIN will cover the area defined by the convxhull of all the points in the input set.

New Pointmap Applications

The set operations for pointmaps are identical for segmentmaps: PointMapIntersect, PointMapDifference, PointMapMapSymetricDifference, PointMapMapUnion, PointMapMapRelate. The only difference is pointmap intersect accepts Pointmaps, Segmentmaps or Polygonmaps as input. It will use the intersection of segments and boundaries to determine the intersection points.

PointMapPointInSegment

A convenience application that determines a suitable point in a segment to determine its “middle”. This can be a real centroid, an existing vertex that is the best estimate or a point on of the edges that is closest to the centroid.

The three options in one map. Triangle=Centroid, Circle=Vertex, Diamond=MiddlePoint.

Syntax
PointMapPointInSegment(input segment map, option)

Input pointmap
The input segment map
Option The option can be “Centroid”,”Vertex” or “MiddlePoint”.





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