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14 votes

How to extract drainage line network from GRASS GIS and QGIS

The answer will depend on the requirements of your specific workflow and application but I can offer you advise on how a drainage network is generally extracted from a digital elevation model (DEM). ...
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  • 10.8k
10 votes

Which tools and methods can be used to create isochrones?

You could have a look at the Targomo API (formerly Route360˚), a pretty simple but powerful JS library which you can use with Leaflet (or even Google maps if you like). It adds travel time polygons ...
10 votes
Accepted

Average walking distance

The solution: OD Matrix analysis You can do that with OD Matrix analysis (see here for the concept). This can be done in QGIS using the plugin QNEAT3. Once installed the plugin, use OD Matrix from ...
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  • 40k
9 votes

Creating Isochrones in QGIS?

Just recently, a new QGIS plugin, called OSM Tools, has been published. This plugin utilizes OpenRouteService API to compute routes and isochrones for various travel modes such as car, heavy vehicle, ...
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  • 351
9 votes

Creating Isochrones in QGIS?

The plugin QNEAT3 offers a great tool for this creating isochrones or service areas offline based on your own network. You can run Iso-Areas as polygons or another algorithm: To get isochrones, ...
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  • 24.6k
9 votes

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

You can easily use PostGIS to select roads that don't intersect any other road: SELECT id, geom FROM roads a WHERE NOT EXISTS (SELECT 1 FROM roads b WHERE a.id != b.id AND ...
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  • 12.3k
8 votes

Creating drive time polygons using Open Source tools?

You can use GraphHopper for that task, which also supports different mode like walking or biking and uses OpenStreetMap per default. You'll need some Java coding which explores the road network from ...
8 votes

What are the existing datasets of world maritime routes?

Removed the previous links, which I should have checked more scrutinously, and found some information and shapefiles which hopefully would be of some use: The EEZ Boundaries (Exclusive Economic Zone) ...
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  • 72.2k
8 votes

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

According to the Wikipedia page Longest path problem, this problem ... is NP-hard, meaning that it cannot be solved in polynomial time for arbitrary graphs unless P = NP. Stronger hardness ...
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8 votes
Accepted

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

I think you may be looking for the Graph Diameter of your network. There are a couple of questions on stackexchange that mention this topic, e.g.: The time complexity of finding the diameter of a ...
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8 votes
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Generating dangle point for polyline in QGIS

Extract the vertices from road layer Explode the lines Join each line to the vertices, end points will get line count 1 and all other more than 1 Extract them
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  • 51.2k
7 votes
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Splitting lines at intersections in PostGIS

You might need to use the linear referencing functions to get what you want. For each point, use ST_LineLocatePoint to find out what proportion along the line the point is, then for each pairing of ...
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  • 19.3k
7 votes

Drawing lines between all possible combinations of points using ArcGIS Desktop?

WORKFLOW: arcpy.SpatialJoin_analysis("points","points", "D:/Scratch/many.shp","JOIN_ONE_TO_MANY","INTERSECT", search_radius="1000000 Meters") arcpy.SelectLayerByAttribute_management("many", "...
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  • 21.4k
7 votes

Dragging all vertices at a given point programmatically in PyQGIS

This can be done using QGIS tools that you can enable programmatically. That is, there is no need to reinvent the wheel. Namely, you need to: Click on the Enable Topological Editing button in the ...
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7 votes

Generating dangle point for polyline in QGIS

The specification of any polyline is a little optimistic (given the possibility of duplicate geometries), but for a topologically correct network it can be done using a "Virtual Layer" ...
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  • 7,251
6 votes

How to calculate Network Service Areas in QGIS?

QGIS-only answer QGIS 3 provides out-of-the-box network analysis tools in its Processing toolbox. There are two service area tools: one to compute service areas around a single point and one to ...
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  • 81.8k
6 votes

Creating drive time polygons using Open Source tools?

osrm-isochrone is a small node.js library for generating drivetimes.
6 votes

How to create an OD road distance matrix in QGIS?

UPDATE - QGIS3: Since this seems to be an important topic, I would like to share my answer on a similar question. If you are using the current version of QGIS (3), you can use the plugin QNEAT3. It ...
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  • 2,287
6 votes
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How do you remove isolated roads from a bigger network?

My solution to this was kind of a kludge, but then I was doing a small class project working with a subset of one county's roads so the network wasn't that big and I didn't need to do it as a common ...
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6 votes
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How to get lines and nodes around the confluence point in a network system (line shapefile)?

You work here with a Graph (Graph Theory) and your confluence point is simply a node with a degree (number of edges adjacent to that node) > 2. As you mentioned a Python tag, a solution in Python ...
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  • 50.7k
6 votes
Accepted

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

I think I found an answer myself. The problem seems to be the topology of my network file. If I apply v.clean (snap) followed by v.clean (break or bpol), the nodes can be connected via v.net.steiner ...
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6 votes

Generating dangle point for polyline in QGIS

To just visualize the dangles, use Geomtetry generator with this expression (see below to create actual geometries): difference ( collect_geometries ( array_foreach( array (...
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  • 40k
6 votes

Detecting and making all connected lines in the same direction in QGIS

Compare the azimuth of each line to the line group mean, and reverse the line in each group that deviate the most from the group mean: Refactor fields (or use two field calculators) to calculate: ...
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  • 51.2k
5 votes

How to create an OD road distance matrix in QGIS?

QGIS has all the algorithms necessary, but there is no GUI to create matrices yet. With some Python knowledge the Network Analysis library documentation should get you started.
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  • 81.8k
5 votes

Creating drive time polygons using Open Source tools?

You might want to check out the open Route360° JavaScript API, which works with both Leaflet and Google maps. It returns travel time polygons for the following travel modes: walk, bike, car, transit. ...
5 votes

Connecting points (bus stops), which don't lie on lines (LINESTRING), to network?

The first part of the solution is this: SELECT a.id, ST_Closestpoint(ST_Collect(b.geom_way), a.geom) AS geom FROM point_table a, line_table b GROUP BY a.id, a.geom; This snaps the busstops to the ...
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5 votes

Creating network datasets from OSM data in QGIS?

QGIS cannot convert OSM data into a routable graph. There are other tools which specialize on this task: osm2pgrouting open source osm2po free but not open source Both convert OSM data into a ...
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  • 81.8k
5 votes
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ArcGIS Online Network Service

Esri has collected the road datasets from various vendors, but mostly it is HERE (Nokia). For those countries where HERE doesn't have sufficiently good data, local vendor's datasets were obtained (...
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5 votes

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

You'll need some Python scripting because there is currently no GUI solution for this issue. To get you started, have a look at my point layer to route script for Processing which is based on the ...
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  • 81.8k
5 votes
Accepted

distance matrix with a linear feature

I did have the same the same research question as you. I wanted to calculate the distance from archaeological sites to rivers. I did have access to a hydrological layer by INEGI. I did have rivers as ...
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