What is time geography?
Time Geography is a theory in behavioral geography that explains how people move in time and space. Before the Swedish geographer Torsten Hägerstrand (1916-2004) developed the time geography model, regional scientists generally did not consider time to be a critical variable. They believed that the essential element in the behavior of people was distance. This concept would group all people in the same location together and not consider their individuality. Hägerstrand argued that people could live or work close to a place, but they may never actually visit if they have no time to do so.
Early studies in regional science focused on space alone; a two-dimensional model in which we can easily describe who is where and doing what. This, however, left out an important aspect; time. When are people where? And why? Peoples’ behavior very much depends on time, and events happening at certain times. There are reasons why we are in certain places at certain times and not at other times. There are also reasons why we visit and inhabit some places and not others. Adding time to the dimension does answer questions, such as: why do people choose to live in a certain location? By adding time to the equation, we can map the order in which we do activities, at what time and how much time we spend on them. Ultimately, including time in our geographies will help explain why we live the way we do.
The space-time model
The model that Hägerstrand developed is three-dimensional. The space is mapped out on a horizontal plane. Individuals move over this plane as if they have a GPS tracking device. If you looked at the history of such a device, it would have a continuing line crossing over the location, or just a single dot when stationary. By adding a third dimension vertically, Hägerstrand was able to add time to the model. A stationary individual is then no longer depicted as a dot, but rather a vertical tube. And when the individual moves from one location to the other, it will be a sloping line because travelling a distance takes time. The faster they travel, the higher the gradient of the slope will be. With this new model, a person’s day or entire life could be mapped out with a single connecting line.
This concept is sometimes called the space-time cube, and was so simple and powerful that it changed the course of social studies since its inception in 1969. However, at first its use was limited because the graphics had to be created manually. It was not possible to view different points along the cube without going through another set of elaborate drawing. Now, with the use of GPS and GIS software that automatically creates graphics from databases, it is much easier to draw space-time paths of individuals or groups. Interactive viewing options allow the researcher to highlight certain individuals, locations, or times to get detailed information.
Paths, domains and stations
The line in the space-time cube is called a path. This shows the continuity of people on the move, because people do not live a fragmented life in a few locations, but follow at path that is constantly influenced by decisions made in the past. On a small scale, if you make a left turn instead of a right turn, the events and decisions that follow differ. On a larger scale certain decisions have life-changing consequences. The path shows that all events in our lives are connected.
The horizontal plane in the model is a domain. This can be on any scale, but shows our physical boundaries; the places we could go. Most people are restricted by limitations and cannot go wherever they please. For example, access to private property is often restricted and even public areas like parks and nature reserves are closed at certain times. National borders are also boundaries for many people. In most cases, however, domains are created by habit. You simply follow a similar path in your daily life and stay in a small domain that you are comfortable with.
Stations are locations in a domain, like work or home, in which you move around between floors or rooms, but are considered stationary. If you go to the mall, you may walk for several hours, but are still considered stationary if your domain includes your whole town.
Restrictions in our time-space geographies
People do not lead unrestricted lives. Some decisions in our past put limitations on us. A sex offender can’t go everywhere he/she wants. Someone in prison has even more limitations. However, there are also constraints that everyone must deal with at some point:
Capability constraints are limitations to our physical capabilities or resources. If a person’s body is not able to do something, it limits the possibilities for this person. A handicapped person may not be able to access every place. Someone without a private mode of transportation is also restricted in the places he/she can go within a certain time frame.
Coupling constraints is for activities that you need to share with other individuals and therefore have to be at a certain place and time for. You may want to go to work in the middle of the night, but if you are a shop attendant you cannot go before the shop is open. Or you may want to go to soccer practice every day, but it is only possible when the other team members are present.
Authority constraints are regulations which you have to follow. Locations can be closed to the public, or only open at designated times or for certain people.
Time geography also makes a distinction between flexible and fixed activities. Fixed activities have to take place at fixed places and times, like school or work. The flexible activities can easily be rescheduled or relocated, like shopping or exercise, and have to take place in the gaps between fixed activities. The fixed activities are therefore called space-time anchors.
A space-time prism highlights all possible paths an individual can take. It is anchored by the fixed activities and shows the options of the flexible activities. For example, you have a one-hour lunch break. In the space-time model the time and place that you finish school or work that morning are fixed, as are the time and place you have to start again. The distance you can travel in that time and the time you want to spend stationary at a flexible activity will limit your options. Constraints will also affect the size and shape of the prism. The space-time prism will highlight all the space in the model in which you are able to choose a path. As time goes by, the prism gets smaller, because you need to begin heading back to school or work.
Applications of time geography
Even though the theory of time geography has been revolutionary in social studies and regional geography, it’s practical use has been limited. Technology has made it easier to create models, but it has also made it more difficult to interpret them.
Data collection used to be quite difficult. Sources of data could be national statistics, diaries, or interviews. None of these sources are detailed enough to create a complete path. Technology has made data collection much easier. Mobile phone companies, social networks, and Google can all be used to track peoples’ movement and collect time-space data. Drawing the time-space paths also used to be a time consuming task, but is now done much faster and accurately using software that can create both static and interactive models.
However, because of the internet and mobile technologies we can no longer assume that the activity a person is engaged in can be inferred from their location alone. It used to be that if someone were at home, that individual was most likely engaged in personal activities or, if at the mall, they would be shopping. Now the relation between location and activity is not as strong. Someone could be shopping online at the office, or doing their work on a laptop in a park. Also, the relation between time and activity has changed. You can now shop online for five minutes, go back to work, and finish the purchase an hour later.
Couclelis, H. (2009) Rethinking time geography in the information age. Environment and Planning A, 41(7): 1556-1575.
Kraak, M-J. (2003) The space-time cube revisited from a geovisualization perspective. Proceedings from the 21st International Cartographic Conference.
Miller, H.J. (2004) A measurement theory for time geography. Geographical Analysis, 31(1): 17-45.
Miller, H.J. (2017) Time geography and space-time prism. The International Encyclopedia of Geography.