> Objective

• This section addresses various computations and analyses with vector data 

• The students will learn how to perform network analyses   

• The students will learn how to compute line lengths  

• This section shows how to perform nearest neighbour analysis  

• The students will learn how to perform area calculations  

• This section shows how to determine percentages per class   

• The student will be introduced to analysis tools from the processing toolbox  

• This section show how to perform a height analysis with lines and AHN data  

• This section shows how to perform a population density analysis  

> Index / Table of Contents 

• Introduction  

• Tutorial(s)  

  • Network analysis 

  • Line length calculation 

  • Nearest neighbour analysis 

  • Area calculation 

  • Class percentages 

  • Street intersection density 

  • Analysis tools from the processing toolbox    

  • Height analysis Population density analysis  

• QGIS installation  

> Summary and Highlights 

Introduction 

Vector data can be used directly to analyse geographical data, but it might also be useful to first compute new data like area data. The following tutorials show some analyses and computations that can be done with vector data.

Tutorial(s) 

Network analysis 

Network analysis can be used to find distances, travel times and shortest paths between two locations.  

• Define the shortest and fastest path   QGIS Training manual: “6.3. Network Analysis” Language(s): English  Chapters: follow along: the tools and the data, calculate the shortest path (point to point), try yourself fastest path, follow along: advanced options, shortest path with speed limit, service area (from layer), in conclusion, what’s next   https://docs.qgis.org/3.10/en/docs/training_manual/vector_analysis/network_analysis.html  

• Build a road network and define the shortest path between two points in the city of Washington DC   Ujaval Gandhi: “Basic Network Visualization and Routing (QGIS3)”/”Basis netwerk visualisatie en routeren (QGIS3)”  Language(s): English, Dutch   Chapters: overview of the task, get the data, procedure  EN: https://www.qgistutorials.com/en/docs/3/basic_network_analysis.html  NL: https://www.qgistutorials.com/nl/docs/3/basic_network_analysis.html 

• Find out the facility with the least travel distance from each address in the city of Washington DC   Ujaval Gandhi: “Locating Nearest Facility with Origin-Destination Matrix (QGIS3)”/ “Dichtstbijzijnde faciliteit zoeken met Origin-Destination Matrix (QGIS3)”  Language(s): English, Dutch   Chapters: overview of the task, get the data, procedure  EN: https://www.qgistutorials.com/en/docs/3/origin_destination_matrix.html   NL: https://www.qgistutorials.com/nl/docs/3/origin_destination_matrix.html 

• Define areas within 15-minutes of walking distance in the metro rail station data for Kochi, India  Ujaval Gandhi: “Service Area Analysis using Openrouteservice (QGIS3)”/”Analyse Servicegebied met Openrouteservice (QGIS3)”  Language(s): English, Dutch   Chapters: overview of the task, get the data, procedure  EN: https://www.qgistutorials.com/en/docs/3/service_area_analysis.html  NL: https://www.qgistutorials.com/nl/docs/3/service_area_analysis.html   

• Determine the travel times to a chosen location in the city of Bangalore, India   Ujaval Gandhi: “Travel Time Analysis with Uber Movement (QGIS3)”/”Reistijd-analyse met Uber Movement (QGIS3)”  Language(s): English, Dutch   Chapters: overview of the task, get the data, procedure  EN: https://www.qgistutorials.com/en/docs/3/travel_time_analysis.html   NL: https://www.qgistutorials.com/nl/docs/3/travel_time_analysis.html 

• Define the shortest path    Erik Meerburg (3D geoinformation research group): “Urbanism GIS Course 16: Network analysis”  Language(s): English   Chapters: introduction (start-1:30), geofabric download website (1:30-2:32), OpenStreetMap (2:32-5:13), network analysis (5:13-9:01), open root service (9:01-end)  https://www.youtube.com/watch?v=KW7EFDyl7eM  

Line length calculation and statistics 

Lines can also be analysed in QGIS. The length can be calculated and some statistics can be performed on them.   

• Computation of the total length of railroads in the United States   Ujaval Gandhi: “Calculating Line Lengths and Statistics (QGIS3)”/”Lengten van lijnen en statistieken berekenen (QGIS3)”  Language(s): English, Dutch   Chapters: overview of the task, get the data, procedure   EN: https://www.qgistutorials.com/en/docs/3/calculating_line_lengths.html  NL: https://www.qgistutorials.com/nl/docs/3/calculating_line_lengths.html  

Nearest neighbour analysis 

The nearest neighbour analysis allows to determine the features that are the closest to a given feature.

• Determine the nearest populated place for each location where an earthquake happened  Ujaval Gandhi: “Nearest Neighbor Analysis (QGIS3)”/”Analyse Nearest Neighbor (QGIS3)”  Language(s): English, Dutch   Chapters: overview of the task, get the data, procedure  EN: https://www.qgistutorials.com/en/docs/3/nearest_neighbor_analysis.html   NL: https://www.qgistutorials.com/nl/docs/3/nearest_neighbor_analysis.html 

• Use QGIS spatial statistics within the Processing Toolbox   QGIS Training manual: “6.4. Spatial Statistics” Language(s): English  Chapters: follow along: create a test dataset, creating random points, sampling the data, follow along: basic statistics, follow along: compute statistics on distances between points, follow along: nearest neighbour analysis (within layer), follow along: mean coordinates, follow along: image histograms, follow along: spatial interpolation, try yourself different interpolation methods, in conclusion, what’s next   https://docs.qgis.org/3.10/en/docs/training_manual/vector_analysis/spatial_statistics.html

Area calculation  

The area of a surface can be calculated.

• Calculate surface area of polygons  Hans van der Kwast: “Calculate Areas of Polygons in QGIS”  Language(s): English  Time: 1min 32s  https://www.youtube.com/watch?v=ca_yF7aGXKM  

• Compute area   Erik Meerburg (Geogoeroe): “Oppervlakken berekenen”  Language(s): Dutch  Time: 13min 25s  https://www.youtube.com/watch?v=PTux2E3p7vg  

• Compute total usable area of each building   Erik Meerburg (Geogoeroe): “BAG: totaal gebruiksoppervlak per pand berekenen”  Language(s): Dutch  Time: 10min 15s  https://www.youtube.com/watch?v=vEWzi-GhWVA  

Class percentages 

The percentage of features per class can be determined within polygons. 

• Derive percentage of land use within polygons from CORINE 2018  Hans van der Kwast: “Calculate percentage of land use per subcatchment in QGIS 3”  Language(s): English  Time: 17min 38s  Chapters: introduction (start-1:20), style (1:20-2:15), catchment polygons (2:15-3:00), unique numbers (3:00-3:40), catchment area (3:40-4:30), more steps (4:30-5:15), exporting (5:15-6:35), expression (7:10-9:25), dissolve (9:25-11:50), intersect (11:50-12:40), fix geometry error (12:40-14:00), fix intersection error (14:00-end) https://www.youtube.com/watch?v=xfjg_jpgiTE  

• Derive percentage of land use using the field calculator   Hans van der Kwast: “Calculate Percentage Land Cover per Subcatchment in QGIS”  Language(s): English  Time: 3min   Chapters: introduction (start-0:20), calculate percentage (0:20-1:30), add class names (1:30-end)  https://www.youtube.com/watch?v=U9ePqf1KXmE

Street intersection density computations 

Street intersection density computations refer to determining the number of streets per area.  

• Calculate the street intersection density for the city of Chennai in India   Ujaval Gandhi: “Calculating Street Intersection Density (QGIS3)”/”Dichtheid van straatkruisingen berekenen (QGIS3)”  Language(s): English, Dutch   Chapters: overview of the task, get the data, procedure EN: https://www.qgistutorials.com/en/docs/3/calculating_intersection_density.html  NL: https://www.qgistutorials.com/nl/docs/3/calculating_intersection_density.html 

Analysis tools from the processing toolbox  

The processing toolbox can also be used to perform spatial statistics. Basic statistics (e.g. mean, sum, median calculation) can be done, but also more advanced ones (e.g. nearest neighbour analysis).  

• Use QGIS spatial statistics within the Processing Toolbox   QGIS Training manual: “6.4. Spatial Statistics”  Language(s): English  Chapters: follow along: create a test dataset, follow along: basic statistics, follow along: compute statistics on distances between points, follow along: nearest neighbour analysis (within layer), follow along: mean coordinates, follow along: image histograms, follow along: spatial interpolation, try yourself different interpolation methods, in conclusion, what’s next   https://docs.qgis.org/3.10/en/docs/training_manual/vector_analysis/spatial_statistics.html  

Height analysis  

The height of walls can be analysed by using a vector file with lines and Actueel Hoogtebestand Nederland (AHN) data, which contains the elevation data of the Netherlands. 

• Height analysis based on lines and AHN data in Amsterdam   Erik Meerburg (Geogoeroe): “Hoogte analyse kademuren in QGIS”  Language(s): Dutch  Time: 24min 53s   https://www.youtube.com/watch?v=GrgbN3v1Asc  

Population density analysis 

The population density can be computed and analysed.  

• Population density analysis   Erik Meerburg (Geogoeroe): “Is de Voorhof de dichtstbevolkte buurt van Nederland?”  Language(s): Dutch  Time: 3min 37s   https://www.youtube.com/watch?v=fyQIj5kh9A4

> QGIS Installation

Do you still need to install QGIS? The QGIS installation and update section explains how to install QGIS on Windows and macOS.  

Useful Links 

QGIS Training Manual  

QGIS User Guide  

Ujaval Gandhi (QGIS Tutorials and Tips website)

Hans van der Kwast YouTube channel

Erik Meerburg (3D geoinformation research group) YouTube channel

Erik Meerburg (Geogoeroe) YouTube channel

#QGIS, #Vector data, #Network analysis, #Line length calculation, #Nearest neighbour analysis, # Area calculation, #Percentages, #Street intersection density, #Analyses tools from the processing toolbox, #Height analysis, #Population density analysis