Many students and fresh graduates dabble into GIS without acquiring basic theoretical knowledge of space and location. GIS is about locations and the relationships between them. So, it is important for a GIS analyst to understand fundamental concepts of space and location.
There are three fundamental concepts of spatial analysis:
In this article, we will cover each one of these three concepts in detail. We’ll start with space then location before finally moving to distance.
The human mind measures space in three ways:
- Absolute space
- relative or topological space, and
- cognitive terms
Absolute space can be thought of as mathematical space. It involves the precise measurement of location and space, such as an X, Y, and Z coordinate.
Absolute space should provide an unambiguous description of space. For example, all the information coded on the topographic map shown here, is stored and displayed as a representation of absolute location in space. All locations and features are all described using precise measurements and calculations.
Topological space can be thought of as relative space. Relative space deals with the definition of one location based on the location of another object. These topological relationships represent connectivity between features of the world. In topological space, precise measurement of space is not as important as the relative description of spatial features.
For example, this is a map of the Washington, DC Metro-rail. This map shows all of the routes that the Metro-rail takes. Notice that each stop is evenly spaced on this map. Do you think that each stop is truly evenly spaced in the real world? No, of course not. As a writer of the Metro-rail, are you concerned with how far apart the stops are, or the number of stops before you exit the Metro.
In the situation of being a passenger on the Metro-rail, topological space is much more important than absolute space as your only concern was getting from Point A to Point B is how many times to the doors open before you get off, not how many miles you travel before you exit the Metro.
The third type of space is cognitive space. Cognitive space reflects people’s beliefs, experiences, and perceptions about places. For example, this is a drawing of a university campus from a student’s memory. A freshman student, may know the location of the dorms, the student union, and the dining hall, very well, but not know the rest of campus at all. Conversely, a senior, who lives off campus, may know of the location of every parking lot very well, the locations of many classrooms, locations of the student union, but not be familiar with the location of the dorms.
Location can be described in four ways: absolute, relative, cognitive, and nominal. Let’s start with absolute location.
Absolute location is considered an unambiguous descriptor of the location, typically expressed as a coordinate, such as latitude and longitude. An absolute location cannot be confused with any other location on earth.
Relative location is expressed as both the concept of the site, and a situation. Let’s discuss what that means.
Site vs. Situation
Site refers to the physical attributes of the location, for example, the terrain, soil, vegetation, water source, built environment, and so on.
The situation refers to the location of a place relative to other places and human activities.
Knowledge of site and situation is indispensable in the geography of industrial location.
Cognitive location refers to the personal cognitive images of places and regions compiled from personal knowledge, experiences, and impressions. For instance, Wakulla Springs was considered an important fishing ground and source of food for the native inhabitants. Now, the same source of water is seen as a recreational area. So while this is the same physical location, it is perceived differently based on how it is experienced.
The last way in which we think of location is nominal location. A nominal location is a location that you remember being at when you heard about an event that took place at a different location. For instance, many people remember where they were when they heard the news of the 9/11 attacks. Even though they may not have been near the attacks, the personal memory of the attacks is linked to the location the person was at when they heard the news. Therefore, the location where they heard the news is the nominal location that is linked to the distant location where the event took place.
Final words on location
It is important to note that the systems of measuring representing location for instance absolute, relative, nominal are cultural systems which are embedded in different cultures and worldviews and become inscribed in landscapes. Each culture will have influence on the way in which space is described and perceived.
Distance is described in absolute, relative, and cognitive terms. Absolute distance is a physical unit of measure, for instance, number of miles between downtown Houston, and downtown Toronto. Relative distance is calculated measuring distance, using metrics such as time, effort, or cost. For instance, the distance of two cities maybe 2000 miles apart, which is an absolute description of distance, becomes the distance of two cities measured in tanks of gas, or mileage charge. Last, let’s discuss the cognitive perception of distance. This refers to an individual’s perception of how far things are part. For instance, to some, driving 200 miles between Houston and San Antonio Texas is a reasonable drive. However, for others, a 200 mile drive may seem like a very, very far distance to travel if they are not used to traveling such a distance regularly.
Final words on fundamental of spatial analysis
Lastly, you should be familiar with the first law of geography. Waldo Tobler, professor emeritus at University of California Santa Barbara, Department of geography stated,
everything is related to everything else, but near things are more related to each other
This is widely considered the first law of geography and speaks to the idea that space, and relative and cognitive relationships featured in the space have an influence on the development and interaction of those features.