The Dictionary of Human Geography

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ground. When recorded as a ratio or fraction,

a map’s scale expresses these two distances in

identical units of measurement, with map dis-

tance reported first as one unit, as in 1:10,000

or 1/10,000, which means that a centimetre on

the map represents 10,000 cm on the ground.

(A dimensionless number, 1/10,000, also indi-

cates that an inch on the map represents

10,000 in on the ground.) Fractional repre-

sentations of scale afford a distinction between

large scales such as 1/5,000 and small scales

with huge denominators. Scale may be

expressed verbally, as in ‘one inch represents

one mile’, which some users might find more

helpful than the equivalent ratio 1:63,360

(Goodchild and Proctor, 1997). Maps often

include a graphical scale, on which a carefully

measured line, perhaps subdivided with

appropriately labelled ticks, portrays one or

more typical distances. Unlike ratio or verbal

scales, a graphical scale remains true when the

map is photocopied at a larger or smaller scale.

Cartographic scaleis occasionally confused

withgeographical scale, which refers to the

areal extent of a physical or human process

or phenomenon (seescale). Physical geog-

raphers study entities that range in size from

the small drainage basin in which soil permea-

bility affects stream discharge to the global

stage of atmospheric circulation and climate

change. Social, political and economic pro-

cesses also involve a range of scales, in which

a specific process or phenomenon is usually

associated with a particular level in a hierarchy

ranging from ‘local’ to ‘global’, perhaps with

intermediate levels labelled ‘provincial’,

‘national’ and ‘continental’. When a geo-

graphical phenomenon is represented graphic-

ally, cartographic scale is typically determined

by the size of the page, map sheet or display

screen as well as the map’sgeographical scope;

that is, the area to be covered. That a map

with a broad geographical scope typically

has a small scale, while a map with a narrow

geographical scope often has a comparatively

large scale, underscores the inverse relation-

ship between geographical scale and carto-

graphic scale.

When a major portion of the planet is repre-

sented on a flat map, scale will vary markedly,

not only from place to place but also with

direction (seemap projection). The latter

distortion is particularly obvious on rectangu-

lar world maps, on which the poles are as long

as the equator, while angles and small shapes

are noticeably more distorted in poleward

regions than at lower latitudes. A noteworthy

exception is the Mercator projection, which is

conformal, meaning that scale at a point is the

same in all directions, even though scale varies

enormously across the map. Devised to solve a

specific problem in navigation by rendering

lines of constant geographical direction as

straight lines, the Mercator projection fam-

ously enlarges the size of mid-latitude coun-

tries, relative to tropical nations, and because

north–south scale equals east–west scale

everywhere, the poles lie at infinity. While its

conformality makes the Mercator projection

an acceptable choice for large-scale maps

with a comparatively small geographical

scope, it is a poor framework for world maps

that have nothing to do with navigation.

Because a map’sprojectiondetermines the

type and pattern of distortion, and thus affects

the viewer’s perception of size, shape, distance

and direction, selecting an appropriate projec-

tion is a crucial decision for the map author

(Canters, 2002). An appropriate projection is

especially important for a world map, which

should never include a graphical scale because

extreme distortions are unavoidable. For most

thematic maps, a projection that preserves

relative area is desirable, although the more

extreme distortions of shape found on equal-

area maps of the whole world can be mollified

by a compromise framework such as the

Robinson projection, which attempts to bal-

ance distortions of area and angles (Ipbuker,

2004). The point or line at which a whole-

world map is centred is also important, not

only because distortion is usually low near

the centre but also because territories thus

favoured might be perceived as more import-

ant or accessible than those on the periphery.

Another useful compromise is the interrupted

projection, typified by Goode’s homolosine

equal-area projection, which partitions the

world map into six lobes, for which separate,

locally centred projections minimize shape

distortion for continents and coastlines.

The third principal element of a map is the

graphic coding of geographical features, or

symbolization. Although labels that connote

land masses, oceans and cities can expedite

decoding, standardized symbols that draw on

cartographic conventions, such as blue for

hydrographic features and green for vegeta-

tion, are especially helpful for at-a-glance

assessments of their extent. Also useful are

logical linkages between a map’s content and

the six ‘retinal variables’ readily manipulated

by the map author. As defined by Bertin

(1983), non-verbal cartographic symbols typ-

ically vary in shape, pattern, hue, orientation,

size and greytone value, each of which is

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