The Dictionary of Human Geography

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corridor corresponding to a ground swathe 50

metres across. Because the exaggeration is

much greater at very small scales as well as for

boundariesand contourlines,whichinprinciple

have no width, the map author must not only

eliminate less significant features but also

smooth out meandering streams and contorted

coastlines, displace symbols that would other-

wise overlap, and replace the intricate boundar-

ies of small cities with tiny circles (Dutton,

1999). Visibility and coherence might also re-

quire, as examples, the widening of narrow en-

trances to important bays, the exaggeration of

an important kink (jog) in a road, the amalgam-

ation of distinct but adjoining patches for

forested land, and the blurring of distinctions

between diverse types of cropland. Additional

accommodations are often needed to create

room for important labels – although well-

known abbreviations can shorten street and fea-

ture names, failure to label key features invites

confusion or misinterpretation.

Generalization can be especially problem-

atic with statistical maps, which are notorious

for using aggregated counts or averages to de-

scribe trends incensusdata. A uniform area

symbol for a large, inherently diversenation

or county can suggest an unwarranted homo-

geneity as well as dilute coherent patterns ob-

vious on maps with smaller, more reliable areal

units (Crampton, 2004). Potentially trouble-

some arechoroplethmaps, readily generated

with commercial, off-the-shelf mapping soft-

ware that arbitrarily chops the range from low-

est to highest data values into five equal

intervals, which are then portrayed with a

spectral sequence of hues (blue, green, yellow,

orange, red) that defies the logical darker-

means-more metaphor for area symbols repre-

senting intensity data (Brewer, 1997).

Maps can be categorized in numerous ways,

to reflect their content (e.g., topographic map,

street map), symbolization (e.g., choropleth

map), intended use (e.g.,cadastral mapping,

road map), publisher (e.g., government map,

commercial map), format (e.g. wall map, atlas

map, newspaper map) or medium (e.g. paper

map, video map). Especially noteworthy are

several new map forms that emerged solely or

largely during the twentieth century. Image

maps, rooted in the invention of the hot-air

balloon and photography in the eighteenth

and nineteenth centuries, became an import-

ant mapping technology with the development

of fixed-wing aircraft, helicopters and artificial

satellites, as well as customized cameras and

electronic scanners used in remote sensing

(Dahlberg, Luman and Vaupel, 1990). Also

known as photomaps, image maps have

become a valuable supplement to the conven-

tional topographic ‘line map’, so called

because features are inscribed by crisp sym-

bols rather than inferred from tonal contrast.

Although a single aerial photograph is a per-

spective view, with distances distorted locally

by variation in elevation, photogrammetry

allows the compilation of topographic maps

from overlapping aerial photographs as well

as the efficient generation of distortion-free,

‘orthorectified’ photomaps (as in Google

Earth: http://www.earth.google.com).

Electronic technology has radically altered

the appearance and usability of maps. Ani-

mated maps, first produced on film but now

generated by software, treat time as a scalable

entity and afford historical maps with two

scales, for example, ‘ten seconds represents

one year’ for time and ‘one inch represents

five miles’ for distance (Harrower, 2004).

Dynamic maps afford dramatic fly-by render-

ings of terrain or statistical surfaces, while

interactive topographic maps overcome

conventional treatments of scale and general-

ization by letting viewers zoom in or out.

Interactive maps that let users retrieve add-

itional information by clicking on or merely

rolling over a symbol can remove the inherent

uncertainty of categories on a choropleth map,

or promote a fuller understanding of an un-

familiar country or a local hazardous waste site

(seevisualization). Theinternetnot only

expedites the delivery of geographic informa-

tion, such as timely radar weather maps, but

also affords instant access to historic maps in

public archives and free, advertiser-supported

route maps with supplementary verbal direc-

tions. Societal impacts are especially apparent

in Web-baseddeliberative mapping, which

fosters negotiated solutions of planning or

political issues by multiple authors (Wiegand,

2002), and in a ‘cybercartography’ that

promises a wider exploitation of multi-sensor

formats, an unprecedented degree of integra-

tion and customized products, and inevi-

table challenges for designers, politicians

and scholars (Taylor, 2003). (See alsomap

reading.) mm

Suggested reading

Brewer (2005); Dorling and Fairbairn (1997);

MacEachren (1995); Monmonier (1993);

Peterson (2003); Southworth and Southworth

(1982).

map projection A geometric transformation

of the spherical world on to a flatmap. Map

Gregory / The Dictionary of Human Geography 9781405132879_4_M Final Proof page 437 1.4.2009 3:19pm

MAP PROJECTION