visibility graph

[InsuHong1]

Hello,

I'm looking for the way to construct visibility graph (not visibility analysis) in ArcGIS. visibility graph is:

  "v.net.visibility computes the visibility graph of a vector map containing lines, areas (boundaries) and points. The visibility graph is the graph where the nodes are the end point of the lines, boundaries or simply the points. There is an edge between two nodes if they are 'visible'. Two nodes are visibible if there is no segments in between them, i.e. the edge doesn't intersect any line or boundary in the vector map. This is useful to compute the sortest path in a vector map from any two points. To do this, first you need to compute the visibility graph and from it compute the shortest path using v.net.path or d.path."   (from manual of GRASS GIS)


There are huge amount of research in the field of computational geometry, but they are just about algoritm itself.

[HaraldMathae]

Hello,

I'm looking for the way to construct visibility graph (not visibility analysis) in ArcGIS. visibility graph is:

  "v.net.visibility computes the visibility graph of a vector map containing lines, areas (boundaries) and points. The visibility graph is the graph where the nodes are the end point of the lines, boundaries or simply the points. There is an edge between two nodes if they are 'visible'. Two nodes are visibible if there is no segments in between them, i.e. the edge doesn't intersect any line or boundary in the vector map. This is useful to compute the sortest path in a vector map from any two points. To do this, first you need to compute the visibility graph and from it compute the shortest path using v.net.path or d.path."   (from manual of GRASS GIS)


There are huge amount of research in the field of computational geometry, but they are just about algoritm itself.

Hello iaminsu12,

I'm kind of dealing with the same problem for a university project work. Have you found any proper solution to computing visibility graphs (for LOS Connections, etc.)?

Thanks...

[DanMeehan]

Hey All.  I figured out how to do this but I didn't use the esri tools as they currently do not have a tool set to support the creation of a visibility graph.  There is a request on the "Esri Ideas" page though.  Might want to find it and like it so it gets promoted.

Here's what I did:
- Download QGIS, GRASS, and the GRASS toolbox for QGIS (all free open source software).
- You'll probably need to also download a GDAL library (check out www.maptools.com) Also free.
- Open GRASS and make a new 'mapset'.  (They have their own terminology for things and I'm a rookie so I might be getting these names wrong).  You can import shapefiles directly into GRASS adn save them as a new mapset.
- Open QGIS and make sure the GRASS Toolbox is downloaded.
- Import GRASS mapset into QGIS instance via the toolbox.
- Use GRASS toolbox in QGIS to run the VGA tool (http://grass.osgeo.org/grass64/manuals/v.net.visibility.html)

I glossed over some things but this is the jist of it.  If I can figure it out, you can too.