Questions tagged [network]

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
10answers
43k 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 ...
42
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12answers
8k views

Representing network flows? [closed]

For a project I'm working on, I need to represent network flows over 1,000 zones with directionality. Any suggestions on displaying the information in a nice and non overwhelming way? Any examples ...
34
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10answers
12k views

Seeking alternatives to pgRouting for open source routing / network analysis?

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 ...
24
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5answers
3k 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. ...
20
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6answers
4k 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 ...
18
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3answers
15k 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?
17
votes
10answers
15k 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 ...
17
votes
5answers
17k views

Mapping 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 ...
16
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4answers
7k 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. ...
16
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4answers
4k 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 ...
14
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6answers
3k 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) ...
13
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2answers
6k views

Is there an optimal algorithm to find the longest shortest path in a network?

I have a large set of linear networks and I would like to find the two ends of each network that are the most distant from each other along the network (on the image below, it would be D to K). The ...
13
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2answers
379 views

Finding “terminal” cities on the map

I want to find villages/cities which are ends. That means: I need this villages which are linked to maximum one village on a distance of X km. I'm just wondering how is this algorithm is called (I ...
13
votes
3answers
884 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 ...
12
votes
3answers
3k 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 ...
12
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3answers
6k views

Creating Isochrones in QGIS?

I'm new to QGIS and have tried to create isochrones around points for quite some time. Is there any option to create isochrones on the GUI in QGIS? I know how to create them using pgAdmin (using eg ...
11
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3answers
645 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 ...
10
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3answers
2k views

Shortest path between one point to every other points

I am trying to figure out how to find all the shortest paths from each point and each node of a line to the other points and nodes of lines of this map. I have tried to do it in Python using NetworkX....
10
votes
2answers
9k 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 (...
10
votes
1answer
929 views

How to compute areas of influence in QGIS?

I am trying to create a polygon layer showing polygons that correspond to a closest store. For a set of 30 store locations, the result should be a polygon layer with 30 features, one for each store. ...
10
votes
4answers
2k views

Connecting points (bus stops), which don't lie on lines (LINESTRING), to 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 ...
10
votes
1answer
340 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 ...
9
votes
4answers
6k 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 ...
9
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3answers
5k 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 ...
9
votes
2answers
1k 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
3answers
4k 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 ...
9
votes
1answer
944 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
2answers
582 views

Equal Time Maps for Transit Network (Isochrones) on QGIS

I am on a committee looking to redesign transit service in Sacramento and need to be able to make equal-time maps or "isochrones," like the attached. A prominent difference between transit isochrones ...
9
votes
1answer
301 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 ...
9
votes
1answer
369 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
1k 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 ...
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
2answers
2k views

Shortest path from points in one layer to points in another layer via roads in QGIS

I'm looking for a way to calculate the shortest path from addresses to subway stations via a network of roads. I have the Road Graph plugin, however, the addresses and subway stations are point ...
8
votes
2answers
1k 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 ...
8
votes
1answer
660 views

How to connect nodes via shortest path along network lines with GRASS v.net modules?

My goal: I would like to connect several nodes via the shortest path along a network --> The red nodes in the next image should be connected along the shortest path of the yellow lines. My approach:...
8
votes
2answers
710 views

Switch QGIS proxy settings programatically

I am using QGIS at two offices with different proxy-servers. At the moment I have to change the proxy settings manually every time i switch the office. I was wondering if its possible to change the ...
8
votes
1answer
8k views

How to find the watershed area for each point in the river network using DEM?

Update#1: Thanks, Micha, I have followed your instruction and successfully use the modules in GRASS. I use r.watershed to get the basin raster and the drainage line: and I use r.water.outlet to get ...
7
votes
3answers
1k 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) ...
7
votes
1answer
723 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
2answers
2k views

distance matrix with a linear feature

I would like to use the distance matrix tool (or a similar function) to look at distances between sites (displayed as point data) and large rivers (displayed as linear). I have been following this ...
7
votes
4answers
1k 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
1answer
621 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
3answers
492 views

Shortest Path Analysis with Turns in FME?

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 class which ...
7
votes
1answer
1k 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 ...
7
votes
3answers
4k 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 ...
7
votes
2answers
2k 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 ...
7
votes
1answer
645 views

Steiner tree problem: Optimal routes for Fibre planning on road network

I am trying to solve a large optimization problem where I have a set of nodes on a road network that need to be connected using fibre using the shortest possible amount of fibre. The problem is a ...
7
votes
1answer
989 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 ...
6
votes
2answers
1k 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 ...
6
votes
1answer
7k 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 ...

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