An interconnected set of points and lines that represent possible routes from one location to another, OR in computing, a group of computers connected in order to share software, data, and peripheral devices, as in a local or wide area network.

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55
votes
11answers
23k views

Creating drive time polygons using Open Source tools?

Is anyone using open source tools and/or data to generate drive time polygons that radiate out from a given location? For example, I have used ESRI products like Network Analyst and Business Analyst ...
34
votes
8answers
5k views

Representation of network flows

This is a sample transportation network flow I've done a year ago based on 26 zones. For a project I'm working on now, I need to represent the flows over 1,000 zones with directionality. Any ...
27
votes
11answers
8k views

Alternatives to pgRouting

I was wondering if there are any alternatives to pgRouting tools. Thinking about it for a bit, I think the only alternative is to use R or RPY to do the analysis. Basically I'm trying to solve ...
22
votes
7answers
3k views

Alternatives to Network Analyst

I'm not sure how reasonable this question even is, but it leaves me no less curious after a bit of searching. If I am looking to build a network based on road features and attributes, is Network ...
18
votes
5answers
2k views

How to simplify a routable network?

I have a network graph that I need to simplify in the sense of reducing the number of edges. The idea would be to merge nodes that are located close together and remove the connecting short edges. ...
15
votes
3answers
6k views

How to calculate Network Service Areas in QGIS?

Is there any way in QGIS to apply service area buffers e.g if I have a point on a map I wish to show the service coverage of 1 mile, 2 mile, 3 mile, breaks using the road network?
14
votes
6answers
2k views

What is the best method of visualizing a network on a map?

I have several hundred geo-referenced data points, and the relationships from that point, to other points. I'm trying to figure out the best way of visualizing this on an interactive map (possibly ...
14
votes
8answers
9k views

Which tools and methods can be used to create isochrones?

I'd like to get an idea for what's involved in creating isochrones for a series of sites, with a reasonable degree of accuracy to the estimates. A general outline would be great, though my scenario ...
13
votes
4answers
3k views

How to connect lines in a network?

I have a shapefile of lines and another of polygons. When two or more lines intersect a polygon they should be connected (snapped), but sometimes during manual digitization this doesn't occur. I need ...
12
votes
6answers
2k views

What's an efficient way of detecting road junctions on a map?

I may receive maps from any source for my project, and for the C++ algorithm I'm making, it's imperative for the algorithm to know where road junctions (nodes where more than two road segments meet) ...
12
votes
3answers
775 views

PgRouting - How to clip links when reaching max costs?

I have a polyline shapefile representing a road network and a second shapefile containing points. I would like to use PostGIS (presumably PgRouting) to identify sub-networks or service areas radiating ...
11
votes
5answers
8k views

How can I map a matrix of origins and destinations in QGIS?

I have a central point on a map, and I have other points in a separate layer (the location of a venue, and the origin cities of the venue visitors). Is there a plugin which would generate output ...
9
votes
3answers
2k views

Howto setup and use a remote GIS workstation (QGIS,GRASS,PostGIS)?

I'm using QGIS (and sometimes GRASS and PostGIS) on my 2009 MacBookPro for my thesis project. I was wondering (during an endless batch generalizing in QGIS) if I can set up a server so I can work from ...
9
votes
3answers
377 views

Spatial Network Cleaning

Data used to create a network from has special considerations when cleaning, as minor spatial errors can lead to major bugs in connectivity. What techniques could be considered best practice for ...
9
votes
2answers
679 views

Generate near table for x number of neighbours using arcpy

There are 3 likely scenerios that I am trying to capture near distances for: An interchange subway station, which has 2 or more neighboring stations. That is, the station in question connects 2 or ...
9
votes
1answer
826 views

How can I improve the speed at which QGIS 2.4 handles network data? (Seems much slower than 2.2 - even with small datasets)

I recently downloaded and installed QGIS 2.4 Chugiak on a Windows 7 64-bit machine with a quad core processor and 8GB RAM. I'm having a few problems using datasets of all sizes from a network drive - ...
9
votes
1answer
276 views

How to create a branch network from several input points to an unique outlet in minimizing the distances?

I am searching a way to "hydrologically" connect upstream points to a unique downstream outlet by creating an optimized stream network as pictured below... The cummulated lenght of the stream lines ...
8
votes
4answers
3k views

How to find dead-ends in road network using ArcGIS for Desktop or GRASS?

I'm trying to remove all the dead-end roads in a road dataset (lines) that are less than 100m long. How do I identify roads that are dead-ends (no exit)? The 100m part is easy. I know how to use ...
8
votes
2answers
2k views

Selecting only canals that are connected to reservoirs?

I have a polygon layer of water reservoirs and a polyline layer of canals. In my data, some canals are originating from reservoirs, and leading to other canals. On the other hand there are some ...
8
votes
3answers
3k views

How to emulate Google Maps driving directions using pgRouting?

Would like to emulate google maps' driving directions functionality but use pgRouting instead. google's data over the project area & scale is quite a bit off so we want to use our own transport ...
8
votes
3answers
2k views

How to create an OD road distance matrix in QGIS?

I'm looking for the steps required to produce an origin-destination (OD) cost matrix. What I'm looking for is a matrix of road distances. The distance matrix tool only produces euclidian distances. ...
8
votes
1answer
262 views

Large survey on unconnected underground networks

We (read I) are currently surveying all the stormwater pits and pipes in our shire, and have run into a few issue with handling unknown network connections. The problem is that a lot of our network ...
8
votes
1answer
186 views

Can GRASS compute the line graph representation of an input graph?

I'm interested in computing a line graph for an input graph, preferably in GRASS since I'll be using other GRASS network analysis tools afterwards. I couldn't find any reference to line graphs in the ...
7
votes
1answer
437 views

Do ModelBuilder or Geoprocessing tasks run slower if screen locked?

Is it true if you are running ModelBuilder or a geoprocessing task on a large raster\vector dataset then locking the computer would that cause the ModelBuilder or any geoprocessing to run slower? Is ...
7
votes
3answers
3k views

How to compare 2 polyline datasets?

I have a network data set for footpaths which I have generated through the collation of path networks from a variety of sources. I want to compare this with another dataset which also contains a path ...
7
votes
1answer
3k views

What are the existing datasets of world maritime routes?

I have a list of cargo ports of all over the world and need to show some port-to-port trips on a map, and also to compute lengths of these trips. For that, I need a dataset of actual maritime routes (...
7
votes
2answers
747 views

Is there an open source tool to planarize graphs?

I read about the planarize function in ArcGIS, which seem to do exactly what I want. Is there a similar feature in QGIS or another free tool? I have a shapefile with various shapes intersecting each ...
7
votes
1answer
205 views

Visualizing road Intersections & connections in ArcGIS

I am working with polylines (roads) in ArcGIS and I was wondering if there is a possibility to somehow show intersections as well as connecting parts of all the different road-segments. Also, would ...
7
votes
4answers
507 views

Automatic matching of two street networks

I'm faced with the problem of matching two street networks. I have these two differently sourced networks. The links in each network can be segmented, i.e. there is not necessarily a single whole link ...
7
votes
3answers
174 views

Shortest Path Analysis with Turns

Problem: Using FME and a road networks dataset, I am trying to find the shortest path from A to B, while taking into consideration of turning width (say for a truck). I have created a point feature ...
7
votes
2answers
1k views

Conflating Two Network Datasets in ArcGIS

I am looking to merge two network datasets in ArcGIS 10.0. I have an ArcInfo license and have trawled this forum but am looking for some clarification. I want to merge two road networks but only make ...
6
votes
4answers
165 views

PostGIS query for selecting features not connected to rest of road network?

I have a dataset of roads in a city stored in a PostGIS enabled database. I would like to identify and remove any feature which is not connected to the rest of the road network. This behavior is ...
6
votes
3answers
735 views

Network distance computations using GRASS

I'm an ArcGIS user who's interested in learning to use GRASS. Can anyone point out resources that will help me in learning how to obtain network distances between (1) residential locations (points) ...
6
votes
2answers
426 views

How can I turn a vector layer into a graph G = (V, E)?

I have a number of rail networks, in the form of shapefiles of the "line" type. I want to turn them into a more abstract graph format, i.e. the kind with vertices and edges, not chart-type graphs. ...
6
votes
2answers
3k views

Segment road network line shapefile into new equal length segments line shapefile?

I would like to subdivide a road network for an entire state into segments of equal length. So, Highway X would be divided into 0.5 mile segments, with a record for each segment, and Highway Y would ...
6
votes
1answer
1k views

How to generate a point distance matrix using shortest network distance?

My problem is as follows. To start with, I have the following spatial datasets: A road network; 13,000 odd point locations representing populated localities (ie places where people live); Service (...
6
votes
3answers
2k views

Find a proper path between two nodes in a grid

This question is about finding a proper path (route) between two nodes (P,Q) in a grid (i.e., graph, network, ...). In our concept, we define a path proper (nice) if it is the most similar* to the ...
6
votes
1answer
824 views

calculate slope for a road network

I am working on a road network for routing operations using postgis and QGIS. I am new to both of these tools and need to calculate the slope for each edge (by retrieving the Z value for the start ...
6
votes
1answer
567 views

How to find the shortest path within a polygon? [closed]

I am trying to find a way to calculate the shortest path from one point to another without crossing the boundaries of a polygon. I would like to do it with QGIS as I do not have access to ArcGis. It ...
5
votes
3answers
2k views

Tracing up a stream network & tabulating attributes of polygons it passes through

I have an ArcGIS question that is either very easy or impossible (my favorite kind). I am somewhat inexperienced when it comes to dealing with network analysis, so maybe I'm missing something major ...
5
votes
2answers
960 views

How to find the watershed for each outlet point and sum values within it?

I have the following files to work with: Stream network of a basin; Outlet points for each segment* of the network and Points which represent water withdrawals along of the stream, which are not ...
5
votes
1answer
4k views

How to find network distances between two sets of origins and destinations?

I'm learning how to use Network Analyst, and I'm not entirely sure what to do (or search for). My objective is to measure the nearest distance from the red circles to the blue circles along a road ...
5
votes
1answer
130 views

Is there a way to minimize turns in Network Analyst routing?

I have a network of pedestrian routes and I want to provide them with clean directions, but Network Analyst chooses the first route that it can turn towards destination and gives me a zig-zag road. Is ...
5
votes
2answers
2k views

Are there any open source network analysis tools?

A researcher in my field* recently created an "Urban Network Toolbox", an ArcGIS extension built upon Network Analyst. It calculates a number of measures on urban networks, such as betweenness and ...
5
votes
1answer
419 views

Workflow for adding Pipe Systems to QGIS

I want to layout a concept design for a sewer main in QGIS. I have a variety of background information: Aerial Imagery Services from various sources DEM from LIDAR Lot Boundaries I want to ...
5
votes
1answer
948 views

Geometric Network - Listening to network feature connection changes in the IObjectClassEvents::OnChange event

I need to be able to tell when a particular type of feature, that participates in a geometric network, is having its geometry automatically modified due to the geometric network. What i mean is that ...
5
votes
2answers
475 views

How to connect points (bus stops), which don't lie on the lines (LINESTRING), to a network?

I need to connect bus stops (points) to a network layer (OSM data). These bus stops do not lie directly on the lines (see screenshot) nor should their location be moved. I use PostGIS, pgrouting and ...
5
votes
1answer
738 views

Road Topology Problem solution for junction

I am working with a Road Network. I have digitized the lines with AutoCAD Map 3D. Then Imported it to ArcMap. After entering all kind of database I have created Routing Dataset. But unfortunately its ...
5
votes
1answer
1k views

Using QGIS calculate distance of point along a line

I have lots of points, and a road (lines) and I would like to calculate from point A to point B (the distance must route through the roads (lines). I found this QGIS calculate distance of point along ...
5
votes
1answer
389 views

How to create a service area using both streets and buslines in the same network?

I want to create a network analysis more difficult. Therefore, I want to calculate a Service Area around hospitals next to busstops. But: The network does not only consist of roads and pedestrians(...