Vector network analysis

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Vector network analysis

GRASS provides support for vector network analysis using the DGlib Directed Graph Library.

Implemented algorithms

The following algorithms are implemented (GRASS 6.5+):

Vector directions are defined by the digitizing direction (a-->--b). You can navigate either omnidirectionally or differently in each directions as both directions are supported. Network modules provide parameters to assign attribute columns to the forward and backward direction. To see how a vector is directed, use the "display" parameter of d.vect (set display=dir).

  • see the vectorintro "vector map processing and network analysis" help page

Example: Shortest path routing

Common parameters

  • input -

This is the name of input vector map or data source for direct OGR access.

  • output -

This is the name for output vector map.

  • type -

This parameter defines arc type, which can be line or boundary.

  • alayer -

This parameter is a number and defines the arc layer. Vector features can have category values in different layers. This number determines which layer to use. When used with direct OGR access this is the layer name.

  • nlayer -

This parameter is a number and defines the node layer. Vector features can have category values in different layers. This number determines which layer to use. When used with direct OGR access this is the layer name.

  • afcolumn -

This is the number of the cost column for moving in forward direction or forward and backward directions together.

  • abcolumn -

This is the number of the cost column for moving in backward direction.

  • ncolumn -

This is the number of the cost column for moving through nodes.

Extensios

The Turntable module (to be added to GRASS soon)

New ideas

Screenshots


v.net.iso - Split net to bands between cost isolines (direction from centre). Costs of centre node are used in calculation.


v.net.alloc - Allocates subnets for nearest centres (direction from centre). Costs of centre node are used in calculation.


d.path - Find shortest path for selected starting and ending node.

See also

Tutorials


External links