Editing Scale (map) (section)

==Terminology==

===Representation of scale===
Map scales may be expressed in words (a lexical scale), as a ratio, or as a fraction. Examples are:
::'one centimetre to one hundred metres' &nbsp;&nbsp; or &nbsp;&nbsp; 1:10,000 &nbsp;&nbsp;or &nbsp;&nbsp; 1/10,000
::'one inch to one mile' &nbsp;&nbsp; or &nbsp;&nbsp; 1:63,360 &nbsp;&nbsp; or &nbsp;&nbsp; 1/63,360
::'one centimetre to one thousand kilometres' &nbsp;&nbsp;or&nbsp;&nbsp; 1:100,000,000 &nbsp;&nbsp; or &nbsp;&nbsp; 1/100,000,000. &nbsp;(The ratio would usually be abbreviated to 1:100M)

===Bar scale vs. lexical scale===
In addition to the above many maps carry one or more ''(graphical)'' '''[[linear scale|bar scales]]'''. For example, some modern British maps have three bar scales, one each for kilometres, miles and nautical miles.

A lexical scale in a language known to the user may be easier to visualise than a ratio: if the scale is an [[inch]] to two [[mile]]s and the map user can see two villages that are about two inches apart on the map, then it is easy to work out that the villages are about four miles apart on the ground.

A [[lexicon|lexical]] scale may cause problems if it expressed in a language that the user does not understand or in obsolete or ill-defined units.  For example, a scale of one inch to a [[furlong]] (1:7920) will be understood by many older people in countries where [[Imperial unit]]s used to be taught in schools. But a scale of one [[French units of measurement|pouce]] to one [[French units of measurement|league]] may be about 1:144,000, depending on the [[cartographer]]'s choice of the many possible definitions for a league, and only a minority of modern users will be familiar with the units used.

===Large scale, medium scale, small scale===
:''Contrast to [[spatial scale]].''
A '''small-scale''' map cover large regions, such as [[world map]]s, continents or large nations. In other words, they show large areas of land on a small space. They are called small scale because the [[representative fraction]] is relatively small.

'''Large-scale''' maps show smaller areas in more detail, such as county maps or town plans might. Such maps are called large scale because the representative fraction is relatively large. For instance a town plan, which is a large-scale map, might be on a scale of 1:10,000, whereas the world map, which is a small scale map, might be on a scale of 1:100,000,000.

The following table describes typical ranges for these scales but should not be considered authoritative because there is no standard:
{| class="wikitable"
|-
! Classification
! Range
! Examples
|-
| large scale || 1:0 – 1:600,000 || 1:0.00001 for map of virus; 1:5,000 for walking map of town
|-
| medium scale || 1:600,000 – 1:2,000,000 || Map of a country
|-
| small scale || 1:2,000,000 – 1:∞ || 1:50,000,000 for world map; 1:10<sup>21</sup> for map of galaxy
|}
The terms are sometimes used in the absolute sense of the table, but other times in a relative sense. For example, a map reader whose work refers solely to large-scale maps (as tabulated above) might refer to a map at 1:500,000 as small-scale.

In the English language, the word [[Wikt:large-scale|large-scale]] is often used to mean "extensive". However, as explained above, cartographers use the term "large scale" to refer to ''less'' extensive maps – those that show a smaller area. Maps that show an extensive area are "small scale" maps. This can be a cause of confusion.

===Scale variation===
Mapping large areas causes noticeable distortions because it significantly flattens the curved surface of the earth. How distortion gets distributed depends on the [[map projection]]. Scale varies across the [[map]], and the stated map scale is only an approximation. This is discussed in detail below.