The Dictionary of Human Geography

towards bridging the gap have been made in
studies of disease diffusion and war (e.g.
Smallman-Raynor and Cliff, 2004). dg

Suggested reading
Blaikie (1978); Blaut (1977); Haggett (1992).

digital cartography The use of numerical
coding, electronic media and digital com-
puters to collect, manipulate, manage and dis-
play geographical data. Coined in the 1970s,
the term has largely replaced the older rubric
‘computer-assisted cartography’, because
almost all production cartographyis now
computer-assisted. ‘Digital cartography’ seems
destined for obsolescence insofar as most
geospatial data are now ‘born digital’; that is,
originally captured as numbers using aglobal
positioning system (gps) receiver, aerial
photogrammetry orremote sensing, rather
than converted from an existingmapimage
by scanning or a process of electronic tracing
known asdigitizing. In this sense, geograph-
ical data acquired by updating, transforming
or otherwise enhancing the attributes (descrip-
tions) of cartographic objects such as street
segments and land parcels are also born
digital. Because hard-copy, analogue maps
have become more the exception than the
rule, ‘digital cartography’ seems likely to sur-
vive only when writers need an opposite for
‘analogue cartography’. Even so, born-digital
materials, especially useful because they
are readily searchable and easily updated,
challenge conventional practices of map
preservation and copyright (Varian, 2005).
As an endeavour, digital cartography is
closely related togeographic information

systems(gis). In general, the former focuses

on data acquisition, data management and the

generation of reproducible images, while the

latter emphasizes data retrieval and specialized

analysis. These overlapping disciplines share

a common interest in automated map gener-

alization and the display of terrain data.

In addition, digital cartography has a dynamic,

interactive component linked to scientificvisu-

alization and computer animation. Other

shared concerns include standardized terms

and definitions, flexible exchange formats,

efficient methods for ensuring reliability, and

the development of metadata describing a file’s

origin, contents and fitness for use (Nogueras-

Iso, Zarazaga-Soria, Lacasta, Be ́jar and Muro-

Medrano, 2004).

As with GIS, digital cartography recognizes

two principal types of data, raster and

vector. Examples of raster data include land-

cover data acquired from space with a multi-

spectral scanner, digital elevation models

(DEMs) consisting of surface elevations sam-

pled for a grid with rows and columns spaced

30 m apart, and images scanned from histor-

icaltopographic mapsand nautical charts.

The spatial quality of a raster data set is

described by the spatial resolution of the sen-

sor or scanner. By contrast, vector data rely on

lists of point coordinates to describe the shape

and position ofboundarylines, streets and

other linear features, as well as lists of linkages

or adjacencies to specify the boundaries of

polygons representing, for example, counties

orcensus tracts. In addition, attribute data

describe the type of feature, its name or iden-

tifying number, and specialized characteristics

such as the population of acensus tractor

diffusion The structure of Ha ̈gerstrand’s diffusion model

Gregory / The Dictionary of Human Geography 9781405132879_4_D Final Proof page 162 1.4.2009 3:15pm

DIGITAL CARTOGRAPHY