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Map ScaleContents |
Background
Map scale is based on the arithmetic relationship between the distance on a map and the corresponding distance on the earth. It is usually expressed in the following form: 1:10,000, meaning that 1 unit of measurement on the map represents 10,000 of the same units on the earth's surface.
Small Scale
A small scale map is one in which a given part of the earth is represented by a small area on the map. Small scale maps generally show less detail than large scale maps, but cover larger areas. Maps with regional, national, and international extents typically have scales smaller than 1:500,000, and are considered SMALL SCALE.
Medium Scale
Maps with scales between 1:50,000 and 1:500,000 are considered MEDIUM SCALE.
Large Scale
A large scale map is one in which a given part of the earth is represented by a large area on the map. Large scale maps generally show more detail than small scale maps because at a large scale there is more space on the map in which to show features. All maps with scales of 1:50,000 and larger are considered LARGE SCALE.
Scale Concept and GIS
In a GIS, the traditional concept of scale in terms of distance does not apply because the scale of a digital map is not fixed. By zooming in and out, a GIS can display a map at any scale. In a GIS, the term scale is used to indicate the scale of the data from which the map was captured. For example, if a digital map is said to have a scale of 1:100,000, it was captured from a 1:100,000 scale paper map. Because the display size of a GIS map is not fixed, users are often tempted to enlarge maps to very large sizes. For example, a 1:100,000-scale map can easily be plotted at a scale of 1:20,000, however this is not recommended as the underlying data will not support it and it can lead to inaccuracies when making measurements. When combining two or more datasets together is only appropriate if they have an equivalent scale of capture.
Large scale maps typically show more detail than small scale maps, whereas on smaller scale maps there is simply not enough room to show all the available detail, so features such as streams and roads often have to be represented as single lines, and area features like cities, have to be shown as points. This is called Map Generalization.
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Information about this article
Short title: Map Scale
Description: none
Expertise level: beginner
Author: Murray.Brown
Approval status: approved
Approved by: Murray.Brown
Last change: 2009-10-25
Subsection of: Geospatial Data Concepts
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