Geographic Information Systems
What is GIS?
GIS (Geographic Information Systems) is a spatially referenced relational database system that can store, create, analyze and display statistical and spatial information – maps.
Real world features are stored and represented in a GIS in three forms:
• First, a GIS uses points, lines, and polygons, also known as vector data. Its first order of work is to arrange these and project them accurately on maps. Points may be towns or telephone poles; lines could represent rivers or railroads; and polygons could encompass a farmer’s lot or larger political boundaries. However, it is also possible to attach historical data to these geographical places and study how people interacted with and changed their physical environments. The population of towns changed, rivers changed their courses, lots were subdivided, and land was planted with various crops.
• Second, raster data are digital images that can be useful for display or topographical analysis.
• Finally, tabular data are attributes stored in database files.
The power of GIS is its ability to take tabular data and through a relational database, which contain a series of joined or linked tables, combine it with images to represent them visually as layers.
Using GIS for Rural History
GIS software is an effective tool for connecting and comparing otherwise separate maps and tables. Historians have access to many historical maps and quantitative data, but the job of finding large-scale spatial patterns in the latter is tedious. By making it possible to link historical sources to spatial data, GIS facilitates analysis of relationships between people and space.
The software allows researchers to select – either visually or by attributes – and study specific data within a larger set. Selecting by attributes is useful in many ways. For example, using the census a researcher can study extensive rural areas in great detail by selecting only the people in a known region or only those with certain occupations, religions, or ages. In a GIS, the researcher can see a whole subset of these people across a large space or study a specific area based on geographical attributes.
GIS has been especially useful to urban historical geographers, and accurate historical population data is often most available for urban areas. However, social, economic, and environmental historians may also find the methodology useful for doing rural history. Two quintessential aspects of rural life are a close relationship with the environment and the distance from urban areas and other economic and social infrastructure. GIS is particularly well suited to studies of proximity and the analysis of environmental factors such as climate, altitude, and soil quality.
Planning your Project
These steps comprise a useful way to plan an historical GIS project.
1. Identify your thesis
Answering the following questions will determine the scope of the project and the type of analysis necessary: What is the problem I am trying to solve? What are the criteria necessary to solve this problem? What does the literature say? Who is the intended audience?
2. Learn software basics:
There are a number of opportunities to learn how to do the basics in GIS. The Data Resource Centre (DRC) in the University of Guelph Library offers in-class instruction, appointments, online tutorials, and workshops. The Library owns a site license to access to ArcGIS, a GIS software package by ESRI. Advanced training is available through self-paced on-line tutorials at the ESRI Virtual Campus.
3. Extract information from primary documents: The Library’s workshop
“Using statistical data in a GIS” is useful background for this stage.
1. Process the historical material. When you begin to obtain or create these data, be sure to establish data management procedures. GIS requires the usage of many different pieces of data, thus it is very important that attention is paid to file storage and naming conventions of original and altered data. It is important that all data is contained within one main project folder – subfolders within are encouraged.
2. Prepare the research for analysis. Before original data can be used in a GIS, they must often be modified. This can involve a variety of tasks such as converting from analog to digital (scanning and georeferencing paper maps and photos), creating base maps from modern boundary files and historical maps, defining coordinate systems, standardizing fields between maps and tabular data, and verifying and correcting errors.
3. Manage the metadata. Metadata is information about the data. In the same way that one cites information obtained from books and journal articles, a researcher is responsible for citing the data used in a project. Metadata is found in the documentation provided by the data producer. Information contained within typically includes when, how, and who collected the data. It also describes the structure of the attribute tables, as well as information on projection and scale. Any changes to original files or data created by the researcher should also record the above information. ArcGIS 9.x has a module called ArcCatalog which makes managing metadata quite simple.
4. Analyze the results:
This step involves creating the map, chart, or report. It can be very simple (ie: simple reference map showing location of phenomena) or complex (ie: creation of spatial models that simulate a process, predict an outcome or analyze a problem).
5. Presentation of results:
Research results can be presented in map, chart, or report format. Basic knowledge of map design principles needs to be considered in order not to misrepresent your results.