Vector Network Analysis - GRASS-Wiki

Vector network analysis

From GRASS-Wiki

Contents

1 Vector network analysis1.1 Implemented algorithms1.2 Example: Shortest path routing1.3 Common parameters1.4 Extensios1.5 New ideas1.6 Screenshots1.7 See also1.8 Tutorials1.9 External links

Vector network analysis

GRASS provides support for vector network analysis using the DGlib (http://trac.osgeo.org/grass/browser/grass/trunk/lib/vector/dglib/) Directed Graph Library.

GRASS 7 has WxGUI Vector Network Analysis Tool front-end, which supports some of the vector networkanalysis modules.

Implemented algorithms

The following algorithms are implemented (GRASS 6.5+):

Vector maintenance: v.net (http://grass.osgeo.org/grass70/manuals/v.net.html)Shortest path: d.path (http://grass.osgeo.org/grass64/manuals/d.path.html) and v.net.path(http://grass.osgeo.org/grass70/manuals/v.net.path.html)Shortest path between all pairs of nodes v.net.allpairs (http://grass.osgeo.org/grass70/manuals/v.net.allpairs.html)Allocation of sources (create subnetworks, e.g. police station zones): v.net.alloc (http://grass.osgeo.org/grass70/manuals/v.net.alloc.html)Iso-distances (from centers): v.net.iso (http://grass.osgeo.org/grass70/manuals/v.net.iso.html)Computes bridges and articulation points: v.net.bridge (http://grass.osgeo.org/grass70/manuals/v.net.bridge.html)Computes degree, centrality, betweeness, closeness and eigenvector centrality measures:v.net.centrality (http://grass.osgeo.org/grass70/manuals/v.net.centrality.html)Computes strongly and weakly connected components: v.net.components (http://grass.osgeo.org/grass70/manuals/v.net.components.html)Computes vertex connectivity between two sets of nodes: v.net.connectivity (http://grass.osgeo.org/grass70/manuals/v.net.connectivity.html)Computes shortest distance via the network between the given sets of features: v.net.distance

Vector network analysis - GRASS-Wiki http://grasswiki.osgeo.org/wiki/Vector_network_analysis

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(http://grass.osgeo.org/grass70/manuals/v.net.distance.html)Computes the maximum flow between two sets of nodes: v.net.flow (http://grass.osgeo.org/grass70/manuals/v.net.flow.html)Computes minimum spanning tree: v.net.spanningtree (http://grass.osgeo.org/grass70/manuals/v.net.spanningtree.html)Minimum Steiner trees (star-like connections, e.g. broadband cable connections): v.net.steiner(http://grass.osgeo.org/grass70/manuals/v.net.steiner.html)Finds shortest path using timetables: v.net.timetable (http://grass.osgeo.org/grass70/manuals/v.net.timetable.html)Traveling salesman (round trip): v.net.salesman (http://grass.osgeo.org/grass70/manuals/v.net.salesman.html)

Vector directions are defined by the digitizing direction (a-->--b). You can navigate either omnidirectionallyor differently in each directions as both directions are supported. Network modules provide parameters toassign attribute columns to the forward and backward direction. To see how a vector is directed, use the"display" parameter of d.vect (http://grass.osgeo.org/grass64/manuals/d.vect.html) (set display=dir).

see the vectorintro (http://grass.osgeo.org/grass64/manuals/vectorintro.html) "vector map processingand network analysis" help page

Example: Shortest path routing

see the v.net.path (http://grass.osgeo.org/grass64/manuals/v.net.path.html) and d.path(http://grass.osgeo.org/grass64/manuals/d.path.html) help pages

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 categoryvalues in different layers. This number determines which layer to use. When used with direct OGRaccess this is the layer name.

nlayer - This parameter is a number and defines the node layer. Vector features can have categoryvalues in different layers. This number determines which layer to use. When used with direct OGRaccess this is the layer name.

afcolumn - This is name of the cost column for moving in forward direction or forward and backwarddirections together.

abcolumn - This is name of the cost column for moving in backward direction.

ncolumn - This is name of the cost column for moving through nodes.

If you are not familiar with layers concept in GRASS see Vector Database Management.

Extensios


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The Turntable module (to be added to GRASS soon)

New ideas

Vector network analysis ideas (please help to realize)

Screenshots

more screenshots from the GRASS website (http://grass.osgeo.org/screenshots/vector.php)

v.net.iso (http://grass.osgeo.org/grass64/manuals/v.net.iso.html) - Split net to bands between cost isolines

(direction from centre). Costs of centre node are used in calculation.


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v.net.alloc (http://grass.osgeo.org/grass64/manuals/v.net.alloc.html) - Allocates subnets for nearest

centres (direction from centre). Costs of centre node are used in calculation.


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d.path (http://grass.osgeo.org/grass64/manuals/d.path.html) - Find shortest path for selected starting and

ending node.

See also

GSoC Network Analysis: many new modules!

Tutorials

Network analysis tutorial (http://www.ing.unitn.it/~grass/docs/tutorial_64_en/htdocs/esercitazione/network_analysis/index.html) by University of Trento, Italy

External links

GRASS GIS: Network Analysis (Subnets within a vector network) (http://www.ossgis.co.cc/2009/01/grass-gis-network-analysis-subnets.html)

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Vector Network Analysis - GRASS-Wiki