Overview: What is GIS?

A Geospatial Information System (GIS) is a type of mapping software that allows users to create maps and perform advanced spatial analysis. Users can map quantitative data, such as census demographic statistics, to uncover spatial relationships. Users can also harness the power of a GIS to assign real-world coordinates to digitized maps. Users can then create new features on their maps, for example railway lines, in a process known as digitization. These features contain attribute data, say for example the railway’s owner or the date that segment was constructed, that enable the user to create historically relevant maps and other visualizations. If a user already has attribute data in a spreadsheet or other tabular format, he or she can use a GIS to assign it to its real-world geographic location on a digital map. The process of linking data—e.g., quantitative or spatial—with actual geographic locations on Earth is one of the unique features of GIS. By contrast, a user could use a graphics software program to show their data on a digital map, or they could use a database program to crunch the numbers of their quantitative data. However, only a GIS can assign this data a geographic location. This affords a level of spatial analysis that graphics software and databases cannot match.

There are currently two notable GIS programs: ArcGIS and QGIS. ArcGIS is a proprietary (i.e., pay-for-use) product suite of geospatial tools developed by Esri, a company involved in the GIS products market. By contrast, QGIS is a Free and Open Source Software (FOSS), and it is freely available to all users. (If you are interested, you can find the source code for QGIS here.) Volunteers maintain and update QGIS.

This textbook is designed for use with the QGIS software; there is no need to purchase proprietary software to complete any of the steps in this guide. However, ArcGIS is the industry standard, and, in some areas, it may be able to perform tasks that QGIS cannot. If you are a student or faculty member at a university, there is a chance that you already have access to ArcGIS. As the GIS concepts that underlie both QGIS and ArcGIS are very similar, those who have access to ArcGIS will likely find this textbook helpful. They are also encouraged to check out the Geospatial Historian website. The same team behind this textbook developed the site’s lessons, which are tailored for ArcGIS.

Example Exercise: Using GIS to Investigate Deforestation

Seeing that GIS is useful for analyzing data by mapping it, let’s take a concrete example to demonstrate this. In this chapter, we will get ourselves up and running with QGIS. Then, we will use QGIS to help us visualize a question that relates to Prince Edward Island, Canada’s smallest province. Island environmental scientists and historians have studied how the amount of forest cover on PEI has changed over time, and QGIS can help us visualize the extent of forest cover and agricultural settlement in different historical periods.

When British settlers first began to arrive on the Island in the late-eighteenth century, they encountered a land that was very densely forested. In the 1860s, an Island newspaper spoke of the topography of the Island that an elderly Islander had witnessed in his younger days. “In his boyhood he has seen the greater part of the country covered with the primeval forest. From every hilltop landwards nothing met his eye but a vast unbroken sea of foliage so dense as almost to appear solid.”^[1]

Yet, over a few decades, Island settlers put in the arduous, manual labour required to clear much of the land. They used the cleared land primarily for farming. While environmental scientists and historians today know that a great amount of deforestation has occurred since the settlement period began, they have sought to measure the amount of deforestation and to map where it occurred. As we will show later in this chapter, GIS has given them the capacity to do this research.