Network Analysis: Finding shortest path in QGIS - Revision history

Joshgoutte: /* Introduction */ Updated version

2021-09-30T18:06:36Z

Introduction: Updated version

Joshgoutte: /* Acquiring QGIS (version 3.20.3) */

2021-09-30T18:05:50Z

Acquiring QGIS (version 3.20.3)

Joshgoutte: /* Acquiring QGIS (version 3.20.3) */

2021-09-30T18:03:32Z

Acquiring QGIS (version 3.20.3)

Joshgoutte: /* Conclusion */

2021-09-30T18:02:32Z

Conclusion

Joshgoutte: /* Network Analysis */

2021-09-30T18:02:14Z

Network Analysis

Joshgoutte: /* Symbology */

2021-09-30T18:02:01Z

Symbology

Joshgoutte: /* Clip tool */

2021-09-30T18:01:49Z

Clip tool

Joshgoutte: /* References */ Added Network Analysis info

2021-09-30T18:00:46Z

References: Added Network Analysis info

Joshgoutte: /* Future work */ Adding a future work section with the Network Analysis in mind

2021-09-30T17:57:27Z

Future work: Adding a future work section with the Network Analysis in mind

Joshgoutte: /* Conclusion */

2021-09-30T17:51:19Z

Conclusion

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 Calculating the shortest distance between two points is a very common spatial problem that appears in our daily life quite often. In [https://www.arcgis.com/features/ ArcGIS] software (not open source), this problem can be solved using
-the Network Analysis tool. We use an identically named tool on QGIS and it is an ideal open source alternative. This tutorial will explore that QGIS tool as a solution for finding the shortest path distance or time by calculating cumulative cost between two points in a network. Installing, activating and configuring the tool in the latest version of QGIS 2.18.13 are the most important steps to start this project. The use of the tool is to measure a cumulative cost based on length between two nodes of a network. Measurements take in consideration either the first case, when the speed limit is the same for all the roads (edges of our network) or the second case, when the speed limit differs for some selected roads.
+the Network Analysis tool. We use an identically named tool on QGIS and it is an ideal open source alternative. This tutorial will explore that QGIS tool as a solution for finding the shortest path distance or time by calculating cumulative cost between two points in a network. Installing, activating and configuring the tool in the latest version of QGIS 3.20.3 are the most important steps to start this project. The use of the tool is to measure a cumulative cost based on length between two nodes of a network. Measurements take in consideration either the first case, when the speed limit is the same for all the roads (edges of our network) or the second case, when the speed limit differs for some selected roads.
 == Data ==

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 == Acquiring QGIS (version 3.20.3) ==
-*You need to install the newest version of Quantum GIS (version 3.20.3 at the time of editing this tutorial) in order to activate the road graph plugin.[[File:QGISlogo2.jpg]]
+*You need to install the newest version of Quantum GIS (version 3.20.3 at the time of editing this tutorial) in order to activate the road graph plugin.
 *You may go to this link : [http://www.qgis.org/en/site/forusers/download.html  QGIS Download] in order to download the QGIS version that is suitable to the operating system you are working on.

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 == Acquiring QGIS (version 3.20.3) ==
-*You need to install the newest version of Quantum GIS (version 3.20.3 at the time of editing this tutorial) in order to activate the road graph plugin.[[File:QGIS2017.jpg]]
+*You need to install the newest version of Quantum GIS (version 3.20.3 at the time of editing this tutorial) in order to activate the road graph plugin.[[File:QGISlogo2.jpg]]
 *You may go to this link : [http://www.qgis.org/en/site/forusers/download.html  QGIS Download] in order to download the QGIS version that is suitable to the operating system you are working on.

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	== Conclusion ==		== Conclusion ==

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 The results should look similar to the screenshot below.
 [[File:OverviewSymb.png|200px|thumb|left]]
 == Network Analysis ==
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 [[File:ComparisonRoad.PNG|200px|thumb|left]]
 == Conclusion ==

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 *Output shapefile is specified by us. Refer to the file folder you created to hold all shapefiles and outputs earlier in the tutorial.
-=== Symbology===
-To improve the visual appeal and usability of the map that we create, we should symbolize the different layers to meet our needs instead of staying with the defaults. Firstly, we will symbolize roads based on their type (Street, Boulevard, Parkway, Highway etc.)
-To that on QGIS, you need to do a rule based classification:
-[[File:Rulebased.png|200px|thumb|right]]
-*Right click on the clipped roads layer
-*Select Properties
-*Choose ''Symbology'' and in the scroll down menu selected "Rule Based"
-*You will then set a rule using an expression such as "SUBCLASS" IN ('HIGHWAY', 'FREEWAY') to combine those two classes of roads
-*This is necessary if you have over 10 road types that you cannot sort otherwise.
-*Classify to as many road names as you want
-The train data can be symbolized with the rail symbol available on QGIS.
-Any other added features that we added can also be customized so the map: tennis court(green dot), wading pool(blue dot), etc...
-We can also label the clipped rinks file in order to see the names of the rinks.
-*Right click on the clipped rinks layer
-*Select Properties
-*Choose "Labels" and at the top of the Labels window, select "Show labels for this layer", using "PARKNAME" as the label field.
-I do not however recommend doing it for the tennis, basketball and wading pools as they share locations in many cases and it could be a cause for clutter.
-The results should look similar to the screenshot below.
-[[File:OverviewSymb.png|200px|thumb|left]]
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+=== Symbology===
+To improve the visual appeal and usability of the map that we create, we should symbolize the different layers to meet our needs instead of staying with the defaults. Firstly, we will symbolize roads based on their type (Street, Boulevard, Parkway, Highway etc.)
+To that on QGIS, you need to do a rule based classification:
+[[File:Rulebased.png|200px|thumb|right]]
+*Right click on the clipped roads layer
+*Select Properties
+*Choose ''Symbology'' and in the scroll down menu selected "Rule Based"
+*You will then set a rule using an expression such as "SUBCLASS" IN ('HIGHWAY', 'FREEWAY') to combine those two classes of roads
+*This is necessary if you have over 10 road types that you cannot sort otherwise.
+*Classify to as many road names as you want
+The train data can be symbolized with the rail symbol available on QGIS.
+Any other added features that we added can also be customized so the map: tennis court(green dot), wading pool(blue dot), etc...
+We can also label the clipped rinks file in order to see the names of the rinks.
+*Right click on the clipped rinks layer
+*Select Properties
+*Choose "Labels" and at the top of the Labels window, select "Show labels for this layer", using "PARKNAME" as the label field.
+I do not however recommend doing it for the tennis, basketball and wading pools as they share locations in many cases and it could be a cause for clutter.
+The results should look similar to the screenshot below.
+[[File:OverviewSymb.png|200px|thumb|left]]
 == Network Analysis ==

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-===Clip tool===
-Now we will clip all of our layers to match the extent of the AOI. Navigate to the Vector menu at the top of the QGIS user interface, put the cursor on Geoprocessing tools and select Clip. You select "Run as a Batch Process". This allows us to clip all of our desired layers at once using one tool (Please note that the Batch Processing Tool requires at least 3 input layers to function).
-[[File:Clip20.png|200px|thumb|left]]
-*Input vector is the layer we want to clip: ''Roads''
-*Clip layer is the ''AOI'' that we just created
-*Output shapefile is specified by us. Refer to the file folder you created to hold all shapefiles and outputs earlier in the tutorial.
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+===Clip tool===
+Now we will clip all of our layers to match the extent of the AOI. Navigate to the Vector menu at the top of the QGIS user interface, put the cursor on Geoprocessing tools and select Clip. You select "Run as a Batch Process". This allows us to clip all of our desired layers at once using one tool (Please note that the Batch Processing Tool requires at least 3 input layers to function).
+[[File:Clip20.png|200px|thumb|left]]
+*Input vector is the layer we want to clip: ''Roads''
+*Clip layer is the ''AOI'' that we just created
+*Output shapefile is specified by us. Refer to the file folder you created to hold all shapefiles and outputs earlier in the tutorial.
 === Symbology===

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 == References ==
+*7.3. lesson: Network Analysis¶. QGIS Documentation. (2020, June 5). Retrieved September 30, 2021, from https://docs.qgis.org/3.4/en/docs/training_manual/vector_analysis/network_analysis.html.
-*ArcGIS. (2014) Sercive Area Analysis. Retrieved Dec 15, 2014   http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#//004700000048000000
+*ArcGIS. (2014) Service Area Analysis. Retrieved Dec 15, 2014   http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#//004700000048000000
-*QGIS. (2014) Download QGIS for your Platform. Retrieved on December 15, 2014 from http://www.qgis.org/en/site/forusers/download.html
+*QGIS. (2021) Download QGIS for your Platform. Retrieved on September 30, 2021 from http://www.qgis.org/en/site/forusers/download.html
-*QGIS. (2014)  Road Graph plugin. Retrieved Dec 15, 2014 http://docs.qgis.org/2.6/en/docs/user_manual/plugins/plugins_road_graph.html
-*QGIS Blog. Anita Gracer (2011).Drive Time Isochrones – An Example Using Finnish Airports. Retrieved on December 16, 2014  from http://planet.qgis.org/planet/tag/drive%20time%20isochrones/
 *City of Ottawa Open Data Catalog (2013).Roadways  Retrieved on December. 15, 2014  http://data.ottawa.ca/dataset/roadways
 *City of Ottawa Open Data CatalogMuseums (2013). Museums  Retrieved on December. 15, 2014 http://data.ottawa.ca/dataset/museums

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 ==Future work==
+This solution could be further improved when we can combine modes of transport, for example, wanting to bike to the train. It can also be improved if we can find a way to incorporate traffic using some indices and the inclusion of real time data would really benefit such a model, however maybe more in a web map than QGIS. Having the data to update construction sites, road closures and other separated incidents that would affect the model would be great but mostly the responsibility of the data supplier. Also for the delivery companies such as UPS, Canada Post could calculate the most cost effective road which a software like this would permit, the possibility to add multiple points would also be pretty good.
-Future work might be creating Drive Time isochrones in QGIS. Site analyses can benefit greatly from using “drive-time” isochrones to define the study area. In ArcGIS this is called Service Area. It might be helpful to check [http://http://pgrouting.org/ pgRouting] open source software to create the nodes network, where each of them would define a start and an end point for different segments that create the network. Check in for more details: [http://planet.qgis.org/planet/tag/drive%20time%20isochrones/ Drving time isochrones].
 == References ==

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	== Conclusion ==		== Conclusion ==