Analysing Traffic Accidents Using QGIS - Heat Maps, Hotspot Analysis, and the Time Controller Panel

Learning Outcomes of this Tutorial

By the end of this tutorial, you will be able to perform the following tasks within 'Quantum' GIS (QGIS):

• Importing point data files (shapefile, CSV)
• Importing satellite imagery basemaps
• Labeling point data using attribute information
• Creating heat maps, point, and kernel density maps
• Learning to use the time controller panel
• Visualizing traffic trends as a finished map

Purpose

The purpose of this tutorial is to create a map that can aid in Traffic Accident Analysis while introducing users to heat maps, point, and kernel density maps, using several tools and plugins within QGIS.

Introduction

QGIS is a free and open source geographic information system (GIS) that is developed and supported by thousands of users and organizations around the world. It's core features include a suite of vector and raster tools that are compatible with many of the most popular geospatial file formats.

The required knowledge level of this tutorial is a basic understanding of GIS. This tutorial incorporates step-by-step instructions and screenshots for each step of the procedures which should be easy to follow along at any skill level.

Techniques

Heatmaps

A heatmap is a visualization method that displays the geographic clustering of a phenomenon. Heatmaps can also be used when clustering points where more points in an area will have higher value compared to less points in the same area. Thus, with a heatmap a concentration of an event's occurrence can be seen.

Hotspot Maps

Hot spot analysis uses statistical analysis in order to define areas of high occurrence versus areas of low occurrence.

Heatmaps Vs. Hotspot Maps

Though seemingly similar and often used interchangeably heat maps and hot spot maps are not identical processes. Both processes are used to visualize spatial data o show occurrences in an event using a colour gradient to indicate high levels of density. However, heatmaps are created by assigning each raster cell to a density value and the entire layer is visualized using a gradient. The resulting visualization affects how the data is interpreted by the viewer and is subjective. Hot spot areas are statistically significant, resulting in a final visualization that is less subjective. The designation of an area as being a hot spot is therefore expressed in terms of statistical confidence.

For more information see this link on the difference between a heatmap and a hot spot map.

Before starting the analysis, you should choose what you want to analyze and determine which tool and what settings suit your needs.

Open Source

The term ‘open source’ refers to accessible, free and redistributable programs available to the public. Compared to more common commercial packages such as ArcGIS, which have costly license subscriptions, open source programs like QGIS are free of charge to use. Additionally, open source programs and data allows individuals to work together to code. This type of model encourages open collaboration. If you would like, feel free to look at available open source technology at OSGeo.

About QGIS

As described on their website, QGIS is a "A Free and Open Source Geographic Information System", and the latest version of the software (v3.26 Buenos Aires as of September 2022) is available for download on their Official Website. Similar to other GIS platforms it can be used to edit, create, visually represent, analyze and export a variety of geospatial data and it is licensed under the GNU General Public License. QGIS is an official project of the Open Source Geospatial Foundation (OSGeo). It runs on Linux, Unix, Mac OSX, Windows and Android and supports numerous vector, raster, and database formats and functionalities.

Installing QGIS

There are several versions of QGIS available for download. For the purposes of this tutorial, we will be using the long-term release version (QGIS 3.22).

• Follow this link QGIS Download to the QGIS site.
• Ensure that you are on the “Installation Download” tab.
  • There are three versions of the QGIS installer available in this tab. The first is a network installer which is not needed for our application, the other two are the latest release (Version 3.26) and the long-term release (Version 3.22). We will be using the long-term release because it provides the most stability and is more widely used due to it receiving minor updates less frequently.

• The slightly older version of QGIS that will be used for the purpose of this tutorial is v.3.22, which can be downloaded by clicking this link.
• Once you have downloaded the software from the QGIS website, follow the step-by-step installation instructions on your computer. After the QGIS v.3.22 LTR is downloaded and ready to execute, double click the QGIS shortcut icon on your Desktop or search for it in the Start Menu. The QGIS window opens, and we are ready to begin.

Example 1

Data

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Downloading the Data

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Editing the Data

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Adding a Base Layer

1. Launch QGIS once you have installed it on your computer and downloaded a suitable dataset to work with.
2. At the top of your toolbar, click the plugin tab and click the "manage and install plugins" item.
3. In the "all" tab, search for the " HCMGIS" plugin and install it to QGIS. Once this is done restart QGIS.
4. Once you are back into a new project layer, click the HCMGIS tab at the top and go to the BaseMap dropdown and select ‘Bing Virtual Earth’.

Specifying a Project Projection

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Loading CSV File Data and Provincial Boundary File

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Customize the Symbology

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Clipping Interpolation Surface to Create a New Raster Layer

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Exporting the Final Maps

Now w The last step of this tutorial will be exporting the map.

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Example 2 M

Editing the Data

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Loading CSV File Data

1. Open QG]

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Clipping ology

Create a clippi

Create a Print Layout

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Creating a Spline Interpolation

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Conclusion

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