Advanced Polygon and Polyline Editing

A polygon or polyline is made up of a series of vertices and edges. Vertices can be moved, deleted or added. Vertices can also be snapped to vertices of other polygon or polyline objects. These shared vertices can then be moved together. See the following topics for further details:

Digitising Network Objects for more information on how to create polygon and polyline objects.
Editing Network Object Geometry for details on how to edit polygon and polyline objects.

More advanced operations can be carried out on polygon and polyline geometry.

For SWMM and InfoWorks networks, the following operations can be performed:

Geometry data of polygon and polyline objects can be cleaned to reduce the number of vertices and to correct self intersection by use of the Simplify Geometry tool.
Lines can be joined together or split into multiple objects. Please refer to the Joining and Splitting Lines topic for further information.
Polygon geometry can be cleaned to remove overlaps between adjacent polygons and to ensure that vertices match on common edges by use of the Crop Overlapping Polygons and Polylines tool.
Selected pairs of polygons of the same type can be combined to form a single merged polygon by use of the Merge Polygons tool.

For InfoWorks networks, the following operations can be performed:

Selected polygon and polyline objects can be changed from their current type to another type. See Changing Line and Polygon Type for details.
Polygon and polyline geometry can be cleaned to remove small gaps between selected objects by use of the Close Gaps and Overlaps tool.
Lines can be trimmed against intersecting lines (for example: where river cross section lines intersect bank lines, the cross section lines can be trimmed against the bank lines prior to building a river reach) by use of the Crop Overlapping Polygons and Polylines tool.
Subcatchments, existing polygons and polygons from GIS sources may be intersected to generate a new set of polygons. Polygons from a single source or from a number of different sources may be intersected.
Generating diagnostic polygons should be carried out for visual inspection of GIS and polygon areas. This procedure identifies the areas where errors have occurred in the recognition of shapes and how they overlay each other.
Lines can be straightened or straightened perpendicular to a link. This is described in the Straighten Selected Lines topic.