Search TipsTopoLineString
A TopoLineString is a topological LineString item that stores data regarding its topological relationship with other topological items and is made up of a series of connected Link items.
A TopoLineString item is a sub-class of a Seed item upon which the definition of a TopoLineString is stored.
Since all of the data held by the TopoLineString item is stored on its base Seed, TopoLineString items are sometimes called SeedChain items.
The seed point itself is never displayed.
TopoLineString Item
TopoLineString groups together a number of contiguous Link items to form a TopoLineString item. This group of Link items define a linear feature such as a road, a fence or a river.
TIP: It may be useful to define TopoLineString items along TopoPolygon item boundaries. This helps to indicate the type of boundary or on routes of a network to indicate road type, name, etc.
TopoLineString items have seed points which are not normally displayed (but may have data attached to them) and an assigned symbol.
TopoLineString items may also have assigned Pen objects so they are displayed in a certain way.
- Click on the first Link item to be included in the TopoLineString item, close to the item's end.
- Do the same with each subsequent Link item and press Enter to finish.
- Alternatively, click on the last Link item to be included in the TopoLineString item. The system will then form a TopoLineString item which includes all intervening Link items, always taking the shortest route between the first and the last Link items.
Properties
- Angle: _angleDeg#
The angle of an item in degrees. - Closed: _closed&
Does the geometry of the item form a closed loop? - Geometry class: _classGeom$
The C++ class used to store an item's geometry. This is handled automatically. You can see what precision an item's geometry is stored with by recognising the geometry classes. - Links: _links$
A list of integers describing the Link items used by this Node, TopoPolygon or TopoLineString item.
Node:
A space-separated list of integers representing the Item IDs of links connected to this node.
A positive value indicates a link entering the node. A negative value indicates a link leaving the node.
e.g. -70 71 -79 80
TopoLineString:
A space-separated list of integers representing the Item IDs of links which constitute this TopoLineString.
The first integer is always 1. The second integer represents the number of links which constitute the TopoLineString. Subsequent integers represent the Item IDs of the links themselves. A negative integer means the direction along the link is opposite to the sense in which it is constructed.
e.g. 1 6 195 -183 161 -187 197 -189
TopoPolygon:
A space-separated list of integers representing the Item IDs of links which constitute this TopoPolygon.
The first integer is the number of loops in the TopoPolygon. The second integer represents the number of links in the first or only loop. This is followed by the Item IDs of the links which constitute the first or only loop. Any remaining integers represent further sets of “number of links/Item IDs”. There are as many “number of links/Item IDs” sets as there are loops in the TopoPolygon. A negative integer means the direction of the TopoPolygon boundary along the link is opposite to the sense in which the link is constructed.
- Topology category: _cluster$
The topological category for the TopoLineString or TopoPolygon item.
Typical categories would be "Road" for TopoLineString items and "House" for TopoPolygon items.