Skip to main content icon/video/no-internet
icon backReturn to Entries

Scale

Within geographic information science, scale has several meanings. To the general public, geographic scale may be most frequently understood in the sense of map scale, shown as a scale bar on a map. More generally, scale is the relationship between an abstract respresentation of something and the real thing, whether this is planet earth or a building plan. From a geographic information science perspective, the most important aspect of scale is how it affects the analysis of spatial data. This entry therefore starts with a definition of map scale, moves on to a discussion of a more generic use of the notion of scale and how it affects geographic analysis, and ends with an overview of one theoretical approach to understanding phenomena over multiple scales.

Scale as a Question of Representation

Map scale states how many units of distance on a map represent a given distance in the real world. This relationship can be expressed graphically in the form of a scale bar; verbally in the form of a description, such as “1 inch equals 1 mile”; or arithmetically in the form of a ratio known as the representative fraction. A representative fraction such as 1:50,000 means that one unit of distance on the map represents 50,000 units of distance in the real world. Map scale is an artifact of the need to reduce reality. In the course of mapmaking, the cartographer has to decide what features to omit and how to abstract from reality. As a result, the map scale carries with it some idea about the degree of generalization that has been applied to the real world and how much detail has been preserved.

In everyday English, if we have a map depicting a continent that fits onto a page or a screen, we talk about a large-scale map, meaning a large area (or spatial extent) is depicted. For cartographers, it is the other way around: a large-scale map depicts a small area, whereas a continent fits only on a small-scale map. The logic here is that the representative fraction for a map depicting a small area (e.g., 1:5,000) is much larger mathematically than the representative fraction for a large area (e.g., 1:100,000). Another way to think of this is that for a given unit of measurement, say, kilometer, we would employ a tiny scale bar on a small-scale map, while the same kilometer scale would possibly not even fit onto the page of a large-scale map. Thus, the size of the scale bar gives us a hint as to how we should use these terms. For better or worse, there are more everyday map users out there than cartographers, and therefore the noncartographic usage of the word generally prevails.

Scale and Resolution

Many geographic information scientists avoid the notion of scale altogether. One reason is the conflicting meaning of large versus small outlined above. Another is that vector-based GIS databases tend to be multiscale, storing the same feature multiple times for different levels of graphic resolution. For example, a city may be represented and stored as a point for cartographically small-scale maps and as a polygon for large-scale maps. Also, while GIS users often state that a vector data set has a specific scale (normally stated as a representative fraction), they are actually speaking only of the scale of the original map from which the data was digitized. In this case, the map scale is used to imply the amount of generalization that was captured in the data. In reality, speaking of map scale with respect to a vector data set that can be displayed at any scale and zoomed in or out on demand is confusing and inappropriate.

...

  • Loading...
locked icon

Sign in to access this content

Get a 30 day FREE TRIAL

  • Watch videos from a variety of sources bringing classroom topics to life
  • Read modern, diverse business cases
  • Explore hundreds of books and reference titles

Read next

More like this

Sage Recommends

We found other relevant content for you on other Sage platforms.

close

Have you created a personal profile? Login or create a profile so that you can save clips, playlists and searches

close
close
close Signed In to profile You are signed in as:
close
Logged in Institution Institution