Computer-Aided Cartography
Author(s): David Rhind
Reviewed work(s):
Source: Transactions of the Institute of British Geographers, New Series, Vol. 2, No. 1,
Contemporary Cartography (1977), pp. 71-97
Published by: Blackwell Publishing on behalf of The Royal Geographical Society (with the Institute of
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Computer-aided
cartography
DAVID RHIND
Lecturerin Geography, University of Durham
Revised MS received 15 September I976
ABSTRACT.
Though beset by problems of definition of terms and duplication of effort, computer-aided cartography has
progressed over the last 25 years from producing almost uninterpretableassemblages of alphabetic symbols to having the
facility for creating any desired graphic image. Two main strands may be distinguished in this development: the 'research'
and the 'topographic'cultures. Recent developments,mainly in the provisionof data, and the need for sophisticateddata-base
managementsoftware, are forcing these two groups to become increasinglyinterdependentand fused.
Numerous benefits have been hypothesizedfor introducingcomputers into map-makingprocesses: these are reviewed,
together with the results of practicalexperience. The methods and equipment used to date and likely future enhancements
are also discussed in relation to the needs of different user groups.
THE definition of terms has become something of an obsession in cartography in recent years
and computer-based techniques have provided another impetus to international codifications
(I.C.A., I973). More specifically, significant emphasis has been laid by geographers (e.g. Waugh
and Taylor, I977) on the existence of a substantive difference between 'computer cartography'
and 'automated cartography'. The first of these is used to denote a process for producing essentially thematic-type maps, typically research products, while the latter is viewed as a process
involving the use of a computer to produce existing-type topographic maps. Such a distinction is
a convenient one, based upon the procedures used to date, the initial sources of innovation and
the sparse availability of topographical data in computer form, but it is ultimately a dangerous
and misleading one which obscures the identical nature of data handling in both 'fields' at the
machine level and the considerable overlap of the subject areas. Thus, for the purpose of this
paper, 'digital mapping' 'automated', 'computer' and 'computer-aided' cartography and 'computer mapping' will be treated as synonymous terms, particularly since no satisfactory entirely
automated cartographic process yet exists.
With very rare exceptions (e.g. Tobler, 1959), few geographers or cartographers were
actually involved at the outset of computer mapping or, less surprisingly, of computer graphics
generally. The first successful attempts to produce graphics from computers were reported in the
early I950S. By the middle of that decade maps were being produced on the now-standard
computer output device, the line printer (e.g. Dobrin, 1952; Inst. of Met., I954; Simpson, 1954),
on the earliest cathode ray tubes (Doos and Eaton, I957; Sawyer, 1960) or on tabulating equipment (Perring and Walters, 1962). Both then and now, meteorologists (Menmuir, 1974),
geologists (Sampson, 1975), geophysicists, geochemists (Webb et al., I973), plant ecologists and
other earth scientists have been the major innovators and users, though a significant growth
in use by central and local government planning staff has occurred over the last 5 years (Gaits,
1975) and most national survey organizations in developed countries have at least carried out some
experiments with automated mapping. By the end of the I96os the SYMAP program, created by
Howard T. Fisher and developed at the Laboratory for Computer Graphics and Spatial Analysis
in Harvard University (Schmidt and Zafft, I975), was running at more than Ioo sites. By 1975
this number had grown to 300; since the majority of these sites were universities, this represents
a considerable growth in the availability of automated mapping facilities to academics in general.
7I
DAVID RHIND
72
Though comparatively recent, these and subsequent developments have not gone unrecorded: by the end of 1975, more than 3000 articles (many in mimeograph form) had been
published on different aspects of automation in cartography(K. H. Meine, 1976, pers. commun.)
and a Commission of the International CartographicAssociation devoted to the subject had been
in existence for five years. A growing number of higher degree theses (e.g. Connelly, I968;
Degani, I970; Brassel, i973; Kadmon, I973; Tomlinson, i974; Waugh, 1974 and Thomas,
1976) have been substantially orientated towards the conceptual or the technical problems of
creating maps with the aid of computers. In terms of financial investment (though the figure is
only a crude estimate), no less than ?20 million have been spent on the development of computerized systems for map production, mostly by sections of national government such as the
United States defence organizations or national survey organizations, together with others such
as the Natural Environment Research Council in the United Kingdom and the Canada Land
Inventory: the real costs of these developments could easily be an under-estimate by an order of
magnitude or more. Only in the period since I972 have many commercial companies become
heavily involved in this field but, even so, it is clear that automated cartographyis a topic of wide
practical and conceptual interest-far exceeding the realm of academic geography. This generalization obscures many of the important differences between the developments in research and
in production institutions. In understanding why automation has been regarded as at least
potentially important to so many groups, we must begin by considering (in so far as they are
known) the requirements and existing procedures of the two end points of the map-making
fraternity-the research worker (occasionally a geographer) and the professional cartographerthen turn to consider the impact of computer processes on these and on the map user in general.
MAP
MAKERS
AND
MAP
USERS
Both groups-research worker and professional cartographer-create maps and make use of
them in all three possible functions: as a data store, as a data display and as a data-linking
mechanism, such as the link between soil memoir and ground provided by the soil map. In
many other respects, however, the requirements, aims and resources of the two 'cultures' are
very different. The research worker is frequently interested in creating a 'one-off' or 'few-off'
series of maps to examine some research finding. Though such maps are sometimes re-drawn
for publication, they tend to be monochrome and linework-dominated. The professional cartographer, however, will often see map-making as an end in itself and, in the United Kingdom at
least, is most often employed to draw medium- to large-scale topographic maps to an unchanging
specification or to plan their production. In the extreme case (the Ordnance Survey) more than
95 per cent of all separate map sheets produced are at i: 10 560 scale or larger (Harley 1975),
are designed for litho printing and are completed using many of the new photo-mechanical
techniques described by Keates (1977). Though there is a heavy reliance by academics on the
professional cartographer through the use of topographic maps for teaching purposes and,
more indirectly, by other research workers through the use of topographic base maps as underlays to geology, soil, land use, slope and many other maps, the indigenous map forms produced
are currently very different in appearance, gestation period and means of production.
It follows, therefore, that the defects of present mapping facilities also differ in so far as
these different map producers are concerned. To many research workers, especially in universities, the major difficulty of map making is probably the limited availability of sympathetic
cartographers who will be able to create acceptable maps from rudimentary sketches and brief
conversations. In addition, the ability to experiment with different presentations, extremely
helpful in such under-defined design situations, is often highly limited because of the scarcity
of draughting resources. Other difficulties for research workers arise in the production of small-
Computer-aided
cartography
73
scale 'thematic' maps, often complicated by the need to use existing map projection graticules
(re-centring a projection or otherwise parameterizing one to be optimal for a specific task is
highly time-consuming (see Maling I973)). Finally, in an increasing amount of academic research
(particularly that based on government sources), the raw data are already in, or are quickly
converted into, machine-readable form; use of manual-based cartography therefore introduces
an extra stage into the work schedule.
For the professional map maker, typically in a government-financed institution, the
primary requirements are normally high accuracy and speed of throughput, with the maintenance, but not necessarily publication, of up-to-date detail. Thus the Ordnance Survey (1975)
provides large-scale plans in printed form and also more up-to-date mapped information through
microfilm in the SUSI (Supply of Unpublished Survey Information) system. A major problem
with cartographic up-dating in a conventional manually based system is that addition of detail
to a master copy eventually necessitatesre
the re-draughting of the storage document, that is the
map, and this is labour-consuming and error-prone. A second problem is that innovation of
improved or additional graphics is often delayed by the need for compatibility with the maps
previously produced at the same scales, since the older maps cannot normally be made available
in the new form. As an example, the only ooccasion inlast
in the
15 years when Ordnance Survey
felt it possible to make significant changes to the graphic form of the one-inch map was when
producing the I: 50 ooo scale maps for the whole of Great Britain. These were published in only
two separate phases, rather than their publication being spread over many years in which case
one inch and I: 50 ooo scale maps would have co-existed.
For the community of map users, the conventional, printed-on-paper map has two overriding advantages: convenience of use through its ease of handling and dense storage of information; and its low unit costs and ubiquitous nature relative to present alternatives. But set against
these are many important disadvantages. One is that the paper map suffers from being scale- and
scale of
window-immutable: apart from the use of insets, it is not possible easily to change thethe
it
or
detailed
to
while
is
also
all
of
to
from
the
move
to
viewing,
impossible
synoptic
map,
part
avoid a situation where items of interest are placed at the edge or corner of general purpose map
sheets. Further, there is still a lack of agreement on what type and detail of information is really
required on 'thematic' maps (see McGrath and Kirby, 1969; Beckett, Tomlinson and Bie, 1972;
Salichtchev and Berlyant, 1976) and a paucity of information on what is preferred and needed
on topographic ones for different purposes (Drewitt,
1973; Klawe, 1973):
because of this and
the traditional method of data storage in map form, the map user is usually faced with more
information than he needs for his specific purpose and separating the items of interest usually
requires manual tracing from conventionally produced maps. Other problems for the user of
these maps are legion-map projections often have undesirable characteristics for specific
individual tasks. While low in unit cost because of pricing policies and government subsidies, the
real cost of producing high-quality cartography by manual means is considerable, particularly if
complex photo-mechanical procedures and multicolour printing are required: in one United
Kingdom multi-colour maps series, for example, it costs at least Lio ooo to carry out the drawing
for and the printing of a run of perhaps 3000 copies, each copy being sold at Li, the stock lasting
as long as 20 years for some areas. The longevity of life of such print runs, allied to the high
cost of up-dating the information and bringing this to the attention of clients, ensures that many
such published maps are long since out of date and frequent pressures are exerted to raise prices
to commercial levels. A final and conceptual (but important) disadvantage of conventional map
forms is that they are variable pass filters-in a general purpose map, small features may be
generalized out of existence or suffer a change of form on re-symbolization, but the effect of
context (as in the 'oasis syndrome') and artistic licence ensure that the map user can never be
74
DAVID
RHIND
really sure of the comparative validity of what he is measuring or reading even within one
hand-produced map. Though this comment is particularly apposite in regard to hand-contoured maps of conceptual surfaces derived from haphazardly distributed sample points, it is
also applicable in more subtle fashions to topographic maps. Provided the map user is informed
of the 'rules' used in compiling a computer-produced map and of any subsequent hand retouching, he knows what may safely be compared.
HYPOTHESIZED
BENEFITS
AND DISBENEFITS
OF COMPUTER-AIDED
CARTOGRAPHY
Several cartographershave regarded the introduction of automation to their field as no more than
another change of tools. Indeed, it has been argued convincingly by a senior staff member of the
Hydrographic Department of the Admiralty (I. Kembers, 1975, pers. commun.), that the introduction of computerized plotting of chart graticules and ornament has had less effect than the
changeover a decade ago from pen and ink-based drawing to scribing. The alternative viewpoint
emphasizes that, since automation can now improve cartographic products over a wide range of
applications, can produce map products which were hitherto impossible, and has also resulted
in quite new skills being needed by cartographers, it is best regarded as a revolutionary rather
than evolutionary event. The Meteorological Office in the U.K. is one institution which has
successfully pioneered the very rapid production of automated maps for production purposes,
to the extent that it is now difficult to conceive of the possibility of wther forecasting without
such aids (Menmuir, I974).
Over the period from the announcement of the Oxford System for automated cartography
(Bickmore and Boyle I964) until 976, some or all of the following benefits of cartographic
automation have been hypothesized by numerous authors (e.g. Littlepage, 1969; Bickmore,
I971; Nordbeck and Rystedt, 972;Gaits, 1975; Stutz, 1975; Radlinski, in A.C.S.M., I976, p. 4;
Bickmore et al., 1976):
more quickly.
more
i. To make existing-typemaps
maps
Superficially, an increase in speed of mapping for automation would seem inevitable, especially
numerous socio-ecnomic studies and maps of the United
when one considers, as an example,n the
Kingdom which appeared betweenI968 and 1974--based on the 1961 Census of Population. In
the circumstances where the statistics are provided by a well-organized branch of Government,
and where their format is known in advance, suitable mapping and manipulation programs are
already available (Coppock,I975; Rhind, i97Cb) and a single location is given to reference a
small data area, then maps can be produced by computer of, say, as many as ioo variables within
a week of the receipt of data. Most of this week is likely to be consumed in human decisionmaking-in assessing class intervals (Evans, 1977) and in checking the output for any data
errors or map specification errors-and thus human, rather than computer, resources may set
the upper limit to what can be achieved.
Considering 'topographic cartography', a speed-up in production would also seem to be an
easy task since even the current high-accuracy, electro-mechanical plotting tables can draw
complex maps at around i to 2 cm/sec. Such an increase in the speed of production of topographic maps is highly desirable in many parts of the world. Even in a highly developed country
like the United States, some 21 6oo00of the 5400ooo 7-5 minute quadrangle, I :24 000 scale maps
required to cover the lower 48 states were not published in 1973 and, of the published ones,
some 8oo000were in need of revision (Radlinski in A.C.S.M., 1976). Similarly, Canada (Harris,
1972) has a recently completed coverage at I :250 000 scale but it will be many years before full
coverage atI: 5000ooo scale is available. The contrast between the speed of hand drawing which
was used to produce such maps and that of the second generation of plotters is extreme: as a
Computer-aided
cartography
75
consequenceof theirmodesof operation,they can oftenplot at around oo timesthe speedof the
more traditionalplotters(though,as yet, their output qualityis not as high as that of the best
flat-bed plotters with optical projectors)and perhaps Iooo times the speed of the average
draughtsman.Unhappilythough,plottingtime is often only a smallpartof the gestationperiod
of high-quality, multicolourmaps. Data compilation,checking, editing, proofing and the
constraints of organizing a work flow through the drawing office and factory can compose up to
90 per cent of the time required to create printed maps (see Keates I974).
Whereonlylow- to medium-qualityresultsaredesired,it is possibleto plot resultsextremely
rapidlyon graphicterminals:maps containing2000 point symbols(gradedsquares)have been
generatedand then plottedby the authorin about20 s on a Tektronix40I4 storagecathoderay
tube or C.R.T. (see Fig. 2) for a computer-determined cost of $I.20. This elapsed time is related
to the available communication facilities and plotting could in theory be reduced to around
0-05s. As yet, plottingof this kindis not availablein colour;thoughcolourcathoderaytubes do
exist, their resolutionand capacityare very poorin comparisonwith the monochromecompetitors. Clearly,then, not all present-typemaps can invariablybe made much more quicklyby
automatedmeans.Only when threeconditionsare satisfied-that the dataare alreadyin digital
form, that they are for simple fixed-sizeand shape areas(such as i km squares)or for areas
where boundaries are already digitized, and where the maps may be presented in monochrome
on cathode ray tubes or on a computerline printer-can very rapid productionof maps be
guaranteed.
To makethese mapsmorecheaply.
Costingthe productionof maps is a complexmatter,only possibleover an extendedperiodof
time. Such costingis furthercomplicatedby introducingcomputersinto the mapping.Since the
amortizationof softwareand of computertime varies greatlyfrom institutionto institution,
evaluationof benefitsis particularlydifficult.In the environmentof a Britishuniversity,comis ll (in 1976) an internally
puting can producefree mappingfacilitiessince computertimesti
free resource.Further,if only ephemeralmaps (drawnon cathoderay tubes or other similar
displays)are produced,it is difficultto maintaina meaningfulrecordof exactlywhat has been
producedand how it was used. In the United Kingdom,however,simple video terminalsare
alreadythe same price as typewriterterminalsand do not consumepaper:the cost benefitsare
even more markedbetween graphicsterminalsand colour-printedmaps, so it is a reasonable
suppositionthat their use and thereforecosting difficultiesmay increasestill further in the
future.
An alternativecost-basedjustificationfor computeruse in cartographyhas been advanced
in relationto the editingof largevolumesof line and boundarydata.Using eithersimplebatch
2.
mode editing (Gardiner-Hill,
1972)
or interactive editing (Bickmore and Bell, 1975; Sippel,
1975;
Kroll, 1975), only those map elementswhich are in erroror out of date need to be replaced,
minimizingthe workof the operatorwho shouldneverneed to redraw(or digitize)morethan a
verysmallsectionof the 'affected'map.The cost justificationsfor this are(at the time of writing)
unproven,but may well grow if the dataare suitablyorganized(see below) and given the continuing diminutionin costs of computerhardwarein contrastto the rising labourcosts.
Perhapsthe most common cost-basedjustificationis the spin-off providedby digitizing
once andyet havingthe possibilityto producemapsat differentscalesby merelyre-plottingthe
results:the tenetis entirelybasedon a presumptionof low plottercostsin comparisonwith those
of the rest of the cartographicprocess.Though some of this was demonstratedlong ago (Cobb,
1971), the most strikingexample to date is the productionby OrdnanceSurvey of 1/1250,
i/io ooo and 1/25 000 scale maps from the same digital data base; the publicationof
1/2500,
76
DAVID RHIND
two Herefordshire I/Io ooo scale maps in late 1976 as new forms of the standard map series
emphasizes that this is more than technical virtuosity. More extreme scale reductions than this
do, however, rapidly encounter severe problems of generalization (Rhind, I973; Stewart, I974).
Automated capabilities for generalization are slowly improving (Lang, 1969; Boyle, 1970;
Douglas and Peuker, 1973; Gottschalk, 1974), but, in any case, it is far from invariable that
published derivative maps differing only in scale from the original publication are required from
the same data.
3. To produce maps whose content is related solely to the user's needs.
If no unequivocal and universal advantage for automation can yet be seen in terms of cost, the
benefits for selection of detail are very real given the disadvantages of conventional maps which
have already been enumerated. Sheet edges become transparentto the user who has his own plotting facilities-thus he can specify any area of interest for which data are stored in machine
form, whether that area is a rectangle super-imposed over the junction of four map sheets or a
highly irregular polygon, and still get maps made to meet his requirements. In addition to
specifying such geographical criteria, the user can specify attribute criteria, for example 'only
plot those houses where the rateable value is greater than 300oper annum' or 'plot all those
regions where the out-migration is greater than io per cent over the last io years'. Such selection
facilities may well depend on the data having been suitably classified before encoding, but the
ability to select features and then to treat the world as being an infinitely extensive plane which
may be sampled at any point are basic to almost all automated cartographic facilities: they are
invariably of value to 'research-type mapping' and in the production of maps of networks, such
as of power lines of different voltages. In addition, they are episodically of great potential importance to map-making institutions because they would minimize problems of re-draughting
caused by a change of sheet lines.
4. To makepossiblemapproductionin situationswheredraughtingandbasicskillsarebecoming
scarce in relation to demand.
Some institutionsin London,for example,were under-staffedin their drawingofficesbetween
1970 and 1974 because of an inability to recruit the necessary skills at permitted salary expenditures.
5. To facilitate experimentation with differing graphical representation of the same data.
Though our knowledge of what is effectively perceived in maps is not yet extensive (Board and
Taylor, 1977), much of the graphic symbolism now used in cartography is not based on good
evidence that it is the 'best' means for conveying the information. There are known advantages
of familiarity with graphic symbolisms but the cost of trying alternatives often prohibits experiment: in an automated system the costs of producing alternatives should amount to little more
than the cost of re-running a plotter and such a cost is trivial if the plotter is a cathode ray tube.
Hence graphic experiments are greatly facilitated if suitable equipment and comprehensive software are available. It is also worth noting that perception experiments in cartography are both
difficult to arrange and evaluate: as controlled experiments, they demand numerous map forms
which differ from one another in no more than one aspect. Automated mapping facilitates the
production of the test material of this kind.
6. To facilitate map making and up-dating when the data are already available in digital form.
In the United Kingdom and the United States at least, much mapping may be carried out from
data already stored in digital form. By mid-1976, more than 00oooplans were available on magnetic tape from Ordnance Survey. The Agricultural Census (Coppock, 1976), the Census of
Population (Rosing and Wood, 197I; Coates, I974; Shepard, Westaway and Lee, I974; Dewdney
Computer-aided
cartography
77
and Rhind, 1975; Gaits, 1975), the Census of Distribution and the yearly'Regional Statistics'
publishedby the CentralStatisticalOfficeare some United Kingdom examplesof mappable
data availablein or triviallyconvertedto machineform (see also E.C.U., I97I). At a regional
level, most health authorities have growing data bases which describe variations of various kinds
in illness incidenceand vaccinationefficacy.Crime recordsare also typicallyautomated.Unfortunately,the differentfilesarefrequentlystructuredin differentwaysso thatcross-referencing,
for examplebetweenagricultureand industryin an area,is not simple.None the less, there are
still increasingtendenciesin the United Kingdomandelsewherein Europeto providesomeform
of spatialreferenceon each item and, if all else fails, this can be used not only to map the individual data files but (usually)to cross-referenceone file with another.An extremeexampleof
file linkageof geographicallyreferenceddatain this way is the workof Rokkanand associatesat
Bergen,who have assembleddata for I2 ooo variablesrelatingto 440 communescoveringthe
wholeof Norwayandwho areextendingthis to coverthe periodfromI837 to I975 (Reve, I975;
Rokkan, 1976, pers. commun.).
7. To facilitatethose analysesof data which demanditerationbetweenstatisticalanalysisand
mapping.
Much of the workpreviouslydenotedas 'statisticalcartography'has involvedcalculationsprior
to the mapping; the productionof frequency distributionsand univariatestatistics to aid
decisions on selection of class intervals is one such example. Such analysis has been limited in the
past becauseof the difficultiesof makingmechanicalcomputationsby hand or by machineand
then manually mapping the results. Now, however, it is entirely possible to carry out some
statistical exercise, map the results, carry out a more refined statistical exercise suggested by the
results, map the new results ... etc. This type of iterativeanalysis,particularlywhere done
interactivelyat a computerterminal,can greatlyspeed analysesand such integratedcapabilities
arelikelyto becomevery commonoverthe next decadesince an obviousneed exists for them in
researchenvironments.Similaranalyticalfacilitiesmay well become common in 'topographic
cartography'since,for example,it is helpfulto havesomepriorknowledgeof the totalnumberof
points or line lengthin a map sectionwhich is to be plotted,in orderto estimateplottingtime;
it is also valuableto knowthe sinuositycharacteristicsof lines in decidingwhich generalization
methodto apply.Parenthetically,it is notablethat, at the presenttime, we still have ratherfew
quantitativeconceptsof what mapscontainby way of length of line, numberof point symbols,
etc. (but see Tienstraand van der Kraan,1975); estimatesof computerstoragespace required
for maps,such as that a typical I :24 00oooscale U.S. GeologicalSurveymap requiresabout ioo00
millionbitsof datastorage(Roberts,i962, Radlinski,in A.C.S.M., 1976, p. 4), arenotveryhelpful
since this is highly dependenton the data compactiontechniquesutilized (see Amidon and
Aiken, 1970; Vaniceck and Woolnough, 1975; Visvalingam, 1976).
8. To minimizethe use of mapsas datastores.
Though heavily criticizedby Robinson and Petchenik(I975), studies of informationtheory
1971) have at least shown that these can act
appliedto maps(Sukhov, 1970; Balasubramanyan,
as extremelydensestoresof 'information'.However,thoughcompact,this methodof storagecan
give rise to problemsof retrievalor up-dating.For example,in some countries-particularly
those withouta nationalcadastre-many maps are used primarilyto store such informationas
the distributionor locationof powercables,sewersand otherundergroundnetworksand wells.
In areasof rapidchangethe mapshaveto be up-datedfrequentlyand, becauseof theirnatureas
workingdocuments,re-drawnquite frequently.Everymanualre-drawingis likelyto compound
errors.Storageof the datain digitalformensuresthat, once correct,the dataremaincorrectand
also that the contemporarysituationor changesover a given time periodmay be plottedat will.
78
DAVID RHIND
9. To createmapsof a kindwhichare extremelydifficultor impossibleto produceby hande.g.
on certainmapprojectionsor stereomaps(Adams,I969; Laughton,WhitmarshandJones,1970;
Sampson, 1975).
io. To create maps in which the selection and generalization rules are explicitly defined and
consistentlyexecuted.
1. The introduction of automation, especially in bureaucratic institutions, often necessitates a
thorough review of how and why existing maps are produced; this in itself can lead to substantial economies.
Where the innovationof computeruse for map productioncomes from an individual
researcherin a university,little is wasted other than his time if the applicationproves unreasonable.In corporatebodies, however, a number of practicalexperienceshave revealed
disbenefits.Few organizationsor individualshave yet writtenon any aspect of the difficulties
encounteredin implementingautomatedsystems,exceptwherethey areexplicitlyjustifyingthe
need for an improvedsystem (e.g. Gaits, I975). The followinglist of disbenefitsis therefore
basedon informaldiscussionswith morethan 50 staff membersin majorNorth Americanand
Europeancentres:
I. To get an initialcommitmentof funds, promisesof rapidresultshave frequentlybeen made.
Few automatedcartographicsystems are yet productiontools and virtuallyno experimental
systemhas workedeitheras efficientlyas promisedor in less thantwice the originallyestimated
period.Much duplicationof efforthas occurred,some of which is evidentin I.G.U. (1977).
The acceptanceof computerizedmethodsandthe acquisitionof equipmentandstaffmakeany
subsequentreturnto manualmethodsalmostimpossible.
Each enhancementof the system often seems essential to obviate bottleneckscreated by a
previousenhancement,that is computerizingthe workproducesa positive-feedbacksystem.In
addition,the moreflexibleany productioncartographicsystemhas to be in termsof producing
differentmapsforms,the moredifficultit is to arrangethat the existingequipmentis efficiently
used at all times.Experimentalsystemsoften seem to makeuse of some piecesof equipmentfor
less than 10 per cent of the time available.
2.
3. Only in very restrictedcircumstancescan existingsystemsyet be shown to be cost-effective.
(cf. Pfrommer, 1975, and above).
4. There is a dangerof producingnew maps becausethe facility is there and is easy to use,
ratherthan becausethese maps are needed.
A few of the now-numerousatlasesproducedfromcensus datausing SYMAP seem to fall into
this category.
5. In a situationin which the technologyand availablesoftwareare changingrapidly,selection
of the most suitableequipmentand programsis a difficultmanagementdecision.
The unit cost of computingpowerhad droppedto approximately2 percent of its I963 cost by a
and networkedlinks betweencomputersholds
decadelater and the adventof microprocessors
out promisesof considerablesavingsin the future.Unlikecomputercentralprocessors,the costs
of plottingand digitizingequipmenthavenot decreasedoverthe last I 0 years,but theirproductivity has increasedby as much as o00 per cent in some circumstances.Currentdevelopmentsin
plotting and (especially)digitizing equipment could produce considerablefurther gains in
throughputfor the large-scaleuser in the mediumterm.
Computer-aided
cartography
79
6. A major staffing problem may arise since computer personnel are often better paid than traditional cartographers.
Not only do different salary scales produce administrative problems, but the admixture of very
different types of personnel may give social problems.
7. The spin-off benefits envisaged may not arise-if for no other reason than a lack of user knowledge of what is possible.
Some of these points will be taken up in more detail later: sufficient has now been said to
indicate that the use of computers is potentially (and sometimes in practice) a powerful aid to
production of different kinds of maps, but that the advantages are sometimes illusory and that
the overall planning of implementation and use of any system is critical if it is to be successful.
DETERMINANTS
OF MAP QUALITY
AND FORM
The concept of quality in map terms is extremely difficult to define (and thus measure) but may
be exemplified by the multicolour map of many different zones, allied to clear typography,
comprehensive legend and aesthetically pleasing appearance. In practice, quality need not mean
accuracy in any absolute sense: geological boundaries are often shown in their correct position
relative to a hand-generalized topographic underlay rather than to the 'correct' position given
by a photographic reduction of a large-scale map. There appears, however, to be a wide consensus that the line printer produces low-quality mapping. Perhaps 90 per cent of all the maps
yet produced with the aid of automation (certainly those published in the geographical press),
have been produced by line printer (see below and Fig. 3). To this extent, 'computer maps'
have become identified as instantly recognizable assemblages of different alphabetic characters,
creating a picture through density variations. Yet this is quite misleading, since at least as long
ago as I97I it was demonstrated that high quality maps indistinguishable from hand-made
products could be produced by computer-based means (Rhind, I97I). Coppock (I975, p. I53)
has argued that 'fuzzy maps' are quite adequate for 'fuzzy data' but, even if acceptable, this
contentious point should not obscure the availability of the technical means to produce by
machine any type of map yet produced by hand.
In any local circumstances, the determinants of what may be achieved in mapping by computer are combinations of the following:
i. The spatial reference or notation used to locate the spatial individual (see Deuker, 1974;
Waugh, 1974; Pfaltz, 1975; Rhind, I975a).
High order spatial referencing, such as that by zonal outlines for data areas, is much more
flexible than lower-order referencing, such as the single-point
gle-point co-ordinate: many more forms of
are
available
for
the
former
than
the latter (except in the special circumgraphical representation
stances where zonal boundaries
are
st neighbour criteria).
Whether all possible forms may be produced does, of course, depend on the equipment available
locally. The lowest level of spatial referencing, represented by a postal address, is a nominal one
on spatial measurement scales and can only be mapped sensibly by reference to some other external information such as the co-ordinates of street end-points. The quality of zonal-type maps is
related in part to the accuracy and the resolution of the boundary co-ordinate strings: boundary
data encoded by digitizing machine are therefore likely to produce much higher quality output
than those produced by manual encoding.
The special case of grid cell mapping (Dewdney and Rhind, 1975) ensures that an apparently low-level spatial reference (point co-ordinate) may be used to produce highly accurate
maps. Grid cell mapping causes complications on all except very special line printers (Coppock,
8o
DAVID RHIND
I975), becausethe standardprint charactersare rectangular.Cells are often printedas assemreduced
blagesof 5 x 3 printingcharactersand the resultinglarge maps are photographically
in size.
2.
The responserate and qualitydemandsof the users.
Variations in response-rate demands are enormous, from the desire for instant displays from
the researchworkerusing a terminalor aftera naturaldisasterto those of the usersof geological
and similarmapsfor teachingpurposes.It has alreadybeen pointedout that high throughputof
mapscan be producedrapidlyonly undercertaincircumstances;high responserateis sometimes
even more difficult to achieve, particularlyif the request was unforeseen by the system
designer.
Demands for higher qualityoutput may be met by simply drivinga plotter more slowly
or by photographicreductionof size of output.If this is not feasible(and the latterdestroysthe
advantageof final-sizeoutput)recourseto commercialplottingservicesmay be necessary.
3. The volume (Tomlinson, I974) and organizationof the data (Peukerand Chrisman,I975;
Visvalingam, 1975).
A line printermap of the i-km grid square1971 populationcensus statisticsof GreatBritain
would be a minimumof 3-35 m high byI-8 m broad.Use of a standardline printerwould increasethis size to aboutI6 m by 9 m if equalscalesin X and Y axeswereretained.Suchvolumes
of dataarethus not suitedto normalfacilitiesand,if no otherequipmentwereavailable,mapping
could only sensiblybe carriedout afteraggregationof the datato largerarealunits. The organizationof largedatasets is also criticalin determiningwhetherselectedvariablesor areascan be
retrievedand mappedwithin the computerresourcesavailable(see section on Geographical
InformationSystems).
4. The type of output device available(see below).
5. The sophisticationof the availablecomputerprograms.
Far more computerprogramsare availablein the literaturefor line-printermappingthan for
use on pen or C.R.T. plotters,thoughthe reverseis probablytrue of commercialsuppliers.
6. The constraintsof design inertia,either througha legislatedneed to maintaincomparable,
country-widecover or throughsatisfactionwith the existingproduct.
In this respectit is strikinghow closely the Abingdonand Swindonone-inch geologicalmaps
producedby the NationalEnvironmentResearchCouncil'sExperimentalCartographyUnit for
the Instituteof GeologicalSciencesand the United States Defence MappingAgency'smap of
Shirazreflecttheir conventionalmap specificationsfor these scales of maps.
THE MECHANICS
OF AUTOMATION
Only digitaldeviceswill be consideredin this section,thoughThomas(1976)has suggestedthat
analoguedisplaysmay be very useful for map depictionand were, in any event, used widely by
the MeteorologicalOfficeuntil recently.It is helpfulto considerthe mechanicalaspectsof automationin cartographyunderfour sub-headings:datacapture,checkingand editingof the data,
of them and datadisplay.These areconvenientsub-divisionsbut do
retrievaland manipulations
not describeexclusivecategories:for instance,one frequentlyused checkingmethodis to plot
the data so as to overlaythem on an existing map; encodingthe data throughdigitizingand
editingthemarealso firmlylinkedin manysystems(e.g. see Boylein A.C.S.M., 1976).FigureI
illustratesa simplificationof the processinvolvedin computerizedmap production.Only the
most commonfeedbackloops are shown: thus checkingand editing are shown as an iterative
8i
Computer-aided
cartography
Retrieval and manipulation
Checking and editing
Capture
>
remote
(surrogate)
sensing
tactile
sensing
map
sources
>
map image creation
listing/plntting 8 visual checks+
automated arithmetic and-logical checks
A
plo?er
kv
historical [
lists
I
Fr.
A
I
multi-element association
or comparison (eg overlay)
>
geographicediting
Display
vector
raster
V
plotter
aptans
!
ehemeral
ephemeral
definitive
1
selection on attribute(s)
+
Lo
^ attribute editing
F
>
selectior on area(s)
>
(master
file(s)
reformating, code
conversion , etc
Jdata from external sources
FIGUREI. The map production process in a computer environment
process. Since details of the procedures involved are now easily available in the published literature (e.g. see Dale, I974), they need only be repeated in summary form here.
Data capture
The first stage normally necessitates the creation and storage of two kinds of description. The
first is the location of the spatial unit-point, line, area, volume or hypervolume, in either Euclidean space using a grid co-ordinate system or by using geographical co-ordinates. The second
involves the assignment of meaning or attribute to the spatial description. In practice, data are
often stored in different forms from that in which they are collected in order to minimize the
space requirements and/or speed processing (Freeman, I974).
Historical lists of data are commonly handled by research workers and their encoding is
simple: a more complex.data source to encode is an existing map. The basic procedures of semiautomated digitizing from such a source were spelled out in descriptions of the Oxford System in
I964 (Bickmore and Boyle, I964), but mechanical problems, other technological considerations
and economics meant that consistently acceptable semi-automated digitizing of maps was not
available until circa I971. In principle, the digitizer operator guides a cursor over the feature to
be encodi d and co-ordinate pairs defining it are generated by the machine (often every tenth of a
second) and stored, together with descriptive information entered via a typewriter, a menu or
by other means (Rhind, 1974b). Significant problems encountered in the large-scale use of this
technique include the large volume of data collected, the slow rate of digitizing (commonly of
the order of i m of line per man/hour for freehand work on complex lines), line-following accuracy and distortions in the source document which lead to overlap or underlap of data plotted for
adjacent map sheets. Careful operational procedures can minimize many of the problems and the
many possible errors at an early stage, but even the use of on-line editing procedures, in which a
small computer is linked to the digitizing table to screen data, check on operator actions, transform co-ordinates directly from table to grid form, etc. (Kroll, 1975; Sippel, 1975; Moritz in
A.C.S.M., I976, p. 68) cannot catch all errors.
82
DAVID RHIND
Attempts to remove at least the human, guiding process from this form of digitizing have
been made since at least
only recently have these been crowned with any real success in
I966:
digitizing of multi-colour maps or of complex line work. The close juxta-position and intersection
of lines in complex fashions, allied to the common use of pecks and broken lines for symbolization and the presence of background 'noise' such as names, have created a much more complex
engineering task than that for the lock-on digitizers used in bubble-chamber photograph digitizing.
None the less, recent successes (Wohlmut in A.C.S.M., I976, pp. 118-26) have indicated
that such automated line following can be highly successful in economic and accuracy terms,
especially if there is a high throughput of similar material in feature-separated form to be digitized. Ryan (in A.C.S.M., I976, p. 102) has indicated the value of on-line forms of flying spot
scanners in digitizing globally related line work such as contours.
A quite different approach to the encoding of mapped data was pioneered by the Rome Air
Defence Centre of the Defence Mapping Agency in the mid-g1960s(Diello, Kirk and Callander,
I969) and even earlier by the Canada Land Inventory (Tomlinson,I967; Switzer, 1975). This
involved the scanning of printing plates or feature separations in such a way that the map was
broken up into black or white (or, at Rome Air Defence Centre, into coloured) squares about
o-i mm across and the image stored as a raster. In most linework-based maps, the result was an
inefficient encoding since a very high percentage of the separation was white and the continuity
consuming and complex task. The method has the advantage, however, that much of the digitizing operation is entirely automatic, extremely rapid and independent of the amount of data on the
map. It is suited for high-throughput, constant map-form uses where the separations are already
available, no functional meaning needs to be given to any symbol (encoded as a series of unrelated black or coloured squares) and where a large computer is available for processing.
Changing graphic form between input and output is often difficult with the resulting data, in
contrast to the situation where the basic stored data elements have a functional context, for
example an 'atomic line segment' might be that section of the centre of a river which also formed
an administrative boundary.
Tactile and remote sensing are extreme points on a scale of contemporary data collection
which is increasingly becoming automated. Environmental remote sensing, in particular, has
undergone dramatic developments in the last decade in terms of tasks successfully accomplished,
variety of sensing platforms, resolution of sensors and the extent to which the returned data are
and capable of automated mapping. Estes and Sengar (1974),
directly machine-ine-interpretable
A.S.P. (I975), Collins and van Genderen (1975and
nd Bernstein (1976) give useful introductions
to the field. Petrie (1970) and others have questioned the utility for mapping of much of the
smaller scale imagery obtained from earth satellites, but Calvocoresses (1975) and many others
have presented results which indicate the value of such imagery for non-altimetric semi-automated mapping. Wang (1974) has pointed out that I0 m contour interval maps at 1/2000 scale
have been made of lunar areas from imagery obtained by a satellite 46 km above the moon,
while Batson and Dwornik (1974) have demonstrated extremely striking computer-enhanced
photomaps produced from digitally stored data. Armstrong and Brimblecombe (1975) and many
others have demonstrated that it is possible to go directly from the digital tapes of the LANDSAT
multi-spectral sensor data through classification procedures to produce interpretable qualitativeunit maps (the LANDSAT imagery is repeated every i8 days and each scene covers an area
approximately i85 km square, being built up of reflectance values for cells 80 m across, the
volume of digital data being 7-6 x io6 bits per spectral band per scene). The value of automated
or semi-automated interpretation and subsequent mapping of such massive data sets is obvious,
Computer-aided
cartography
83
particularlysince recent studies have made it clear that much more can often be extracted
by machineand subsequentlyplotted than is possible by visual interpretationof the simple
'photographs'plottedfrom the totalityof the data.
One, moretraditional,formof remotesensingwhichhas becomepartlyautomatedand has
had some impact on cartography is that based on stero-photography, leading normally either to
the productionof a stereo-compiledtraditionalline map or to an orthophotomap (see Petrie,
1977). Partialautomationof the formerhas been effectedby replacingthe normalplot output
from a stero plotterby shaft encodersand thus producingdigitaldescriptionson tape. For the
geomorphologistand highwayengineer,the direct,digitalterrainmodeloutput froma scanning
is a valuablespin-offfromthe orthophotomappingprocessandis easilymapped
orthophotoscope
as slopes or altitude.Though obtainedfrom small-scalesources,altitude datacoverageof the
entireUnited Statesnow existsand the coverageelsewhereis growing:it is at least conceptually
possibleto producemapsfrom combinationsof this and satellitedata.
Checking and editing spatial data
In a cartographiccontext,editingcan be distinguishedfromup-datingsince manydataused to
produce maps are archival: once error-free, they are never deleted, only supplemented. The
possiblechecksand editingmechanismsfor spatiallydistributeddataaregivenin Rhind(I974b,
I975b)whilenumerousacconts of methodsaregivenin A.C.S.M. (I976). n mostcases,checking andeditingis foundto be an iterativeprocedure:not all errorscan be detectedor removedin
one phase and, in addition,changesto the data sometimesproducenew errors.The growth
in availabilityof cheapcomputingpowerhas ensuredthat the morecheckswhich can be made
re cost-effectivethe
by machine,the more
thediting processwill be, but certainchecks-such as the
exactness of positioning of the centre portion of a line segment-can only be checked by reference
to the source document. Checks which can be made by machine are that no part of the digitized
map is outside a specified window, that no codes or attributes are present other than those
expected by the operator and that boundaries of zones do actually close.
In editing map-source data only a restricted number of general functions are required
(Rhind, 1976), such as 'delete', 'move', 'join' and 'add' feature(s); the system design is thus
straightforward. In conceptual terms, the mode of working is unimportant-the same functions
are used whether in a batch mode (Gardiner-Hill, 1972) or in editing at an on-line terminal. In
practice, increasing use is being made of interactive editing facilities for reasons of convenience
and because they tend to introduce fewer new errors in operation. However, a frequent problem
with the editing of data such as geological boundaries on C.R.T. terminals (as in Fig. 2) is the
lack of displayed topography to act as a frameworkfor moving lines and zones. Some data sources,
such as satellite-based imagery, are difficult to check and edit: indeed.such data are often regarded
as not needing to be checked or edited by the user, following use by the data supplier of such
sophisticated digital correction procedures as those described by Bernstein (1976).
Retrieval and manipulation of data
Until circa 1971, most automated cartographic systems used the simplest possible means of
retrieving their data-sequential reading of the totality and rejecting what was found to be outside
the specified geographic or attribute window. While this was simple, it also meant that certain
tasks readily carried out by the map analyst or by a human cartographer, such as working outwards in a given direction through a street network, could only be achieved by frequent rewinding
of tapes or other devices and reading the data set many times. In its most extreme form, this
method of access would have ensured reading all variables for all areas on a tape of census-type
information in order to obtain a value for one variable in the last area. Clearly this is an absurdly
84
DAVID RHIND
FIGURE2. Using a high-resolution Tektronix 4014 storage cathode ray tube
simple means of organization of the data and is now obsolescent. However, since the organization
of largevolumesof geographicallydistributeddatafor taskswhichoften producemappedoutput
andthe availabilityof computersoftwareto achievecomplexretrievalareinherentpartsof recent
developments in Geographical Information Systems (I.G.U., I972; Tomlinson, I974), this
elementis left to a later section for discussion.
Forms of manipulationwhich should be consideredhere includethe specifictask of interpolation of surfacesthrough haphazardlydistributedpoints in space and the creationof the
digital map image-both achievedby transformationsof the notationused for the data. The
problemof producingsurfacesis not a new one and indeed was one of the earliestattackedby
computer-orientatedearth scientists. Though some conclusionsin the K.O.X. (Kansas Oil
Exploration)projectsuggested that better results could be obtainedby machineratherthan
human interpolation(W. A. Read, I974, pers. commun.),this cannot be regardedas a general
conclusionsince many qualitativeand quantitativedata elementscannotbe built into the vast
majority of existing computer packages (Barrett and Rhind, I975). Peuker (1972) and co-workers
have devotedmuch effortto the structuring(Peukerand Chrisman,I975) and presentationof
Computer-aided
cartography
TABLE
85
I
Types of digital outputdevice
PLOT MODE
raster
vector
ephemeral
alphanumeric
C.R.T.
storage
tube or
refreshed
C.R.T.
definitive
line
printer;
Dresser/
Seiscom
plotters
flat bed
or drum
plotters
IMAGE
PERMANENCE
surfacedata, but it remainsclear that the majorproblemis obtaininga 'likely'as opposedto
'possible'surfacefromthe data.Though it can be arguedthat surfacegenerationis not a cartographicproblem,it has importantside-effectsfor map making,since the type of digitaldescription of surfacecan influencethe graphicsymbolismused, for examplewheretriangulatedproceduresare used for contouring,some indicationshouldbe given of whichdatapointsformedthe
triangles,permittinga visual check on stabilityof the results.Rhind (I975b) has reviewedthe
UniversalKrigingmethod
surfaceinterpolationmethodsavailable,but the autocorrelation-based
for many,though
to
the
most
offer
seems
and
Delhomme,
satisfactory
approach
I975)
(Delfiner
not all, applications.In principle,surfaceinterpolationis an under-definedproblemin machine
terms,in contrastto changeof scale or map projectionand most other automatedcartographic
procedures.
The creationof a map image is an importantstep since, as Rhind (1976) has argued,a
plottingfile whichcan be sent to any plottingdevicewhichis available-be that a colourmicrofilmplotteror a line printer-is an essentialelementin modularityof futurecartographic
systems.
Withoutthis, the mapcreatorneedsan intimateknowledgeof the vagariesof eachkindof plotter;
this is an undesirablecharacteristicif the facilitiesare to be easilyused. In some instancesmap
image file creationis a trivialprobleminvolvingonly a changeof data format.In others, it is
dataas lines on a vector
far from trivial-particularlyif it is essentialto drawraster-organized
display(see below).
Data display
The previoussectionindicatedthatthe type of outputdevicewasa severeconstraintuponoutput
quality.The types of digitaloutput device may be classifiedas in Table I. The rasterplotters
producemap images by area filling: thus the line printeris the crudest commonlyavailable
raster plotter, though computertypesettershave also been pressed into unintendeduse for
mapping.Figure 3 is a line-printermap producedwith specialsymbolismat the Universityof
Edinburghand, in originalform,is almostas good as could possiblybe obtainedby this method
(see Coppock,1975; de Gruijterand Bie, I975; Stoye, 1975).Rapidstridesin technologyhave
produceda varietyof otherrasterplottermechanismsusing electrostatic,ink jet (Smeds, 1973),
electronbeamor laser(Rhind, I974a)technology.One of the most sophisticatedis a 5o-micron
resolutionplotterproducedby SeiscomLtd. for plottingmapson up to sixteendifferentintensities over a metre wide and infinitelylong sheet of film. Ephemeralraster-typemaps are very
-- - --
--
--
--
--
_
F=
- --
__
_=
_-
LEGEND
VALUES ARE GROUPEDIN 6 GROUPS
0.000
FREQ. (
64)
0.422
(
64)
1.154L
(
61)
2.751
(
63)
5.681I
(
63)
10.197
(
l 47.711
65)
FIGURE
3. Line-printermap of horticultureas a percentageof tillage in Englandand Wales by AgriculturalAdvisory
District. Source: Agricultural Census
87
cartography
Computer-aided
l
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0
O
LI
0
0C
44
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1-I
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144
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0
44
0
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88
DAVID RHIND
a
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0
0 ao
"I
0
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0
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IP
0
0
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00
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FIGURE 5.
e
0
0
Q
Computer-contouredmap of intensity of visible light radiationfrom galaxyNGC 4I5I/-I83
S. M. Scarrett)
(provided by
rarely produced, the most common reason for their creation being the sole availability locally of
the standard alphanumeric video display unit: in such use, the display mimics a line printer.
The mode of action of vector plotters in drawing lines as lines, rather than as filling very
thin areas with tiny squares, is much more akin to the human draughting process. A variety of
forms of vector plotters exist, from the crudest ?3000 drum plotters in which pen movement
across the drum and drum rotation combine with pen up and pen down commands to give
positional movement (see Figs 4, 5 and 6) to the ?Ioo ooo, high-accuracy, flat-bed, electromechanical plotters with optical projection of symbols on to photographic film (Figs 7 and 8).
The latter can be typified by the Calcomp 7500 which has a granite plotting surface to ensure
stability. For cartographicpurposes much the most frequently used ephemeral map vector display
is the storage cathode ray tube, in which the image is drawn once and stored on the phosphor of
the tube. Until 1974 this was only available in a small ( 5-cm square) format image area but the
introduction of the 38-cm square Tektronix 40I4 was an important advance (see Fig. 2). Many
other displays are now available of this type, of which the most interesting is perhaps the HRD
Computer-aided
cartography
89
I\
11
FIGURE 6.
I
The concentrationof boron on the island of Unst (data provided by Geochemical Division, Institute of
Geological Sciences and published by permission of the Director)
I laserplotter,whichcanproduceeitherephemeralor permanentimages(StreetandWoodsford,
I975), has a I-m screen, the same interactioncapabilitiesas a storagetube and has a io bit
intensitymodulationfacility,that is it has the capabilityto producecontinuoustone imageslike
photographs,normallyon microfiche.
Some use has been madeby geographersandcartographers
of refresheddisplayssuch as the
IMLAC, in which the imageis re-plottedmanytimes per secondand continuityof perception
is ensuredby the operator'svisualpersistence.Though these offerthe abilityto changeimages
instantly,they aremoredemandingof computerresourcesthanarestoragetubesand the current
speeds of plotting, allied to the normalvolumes of cartographicdata, ensure that flickerand
breakdownof the imageoccurfrequently.It is importantto note that all vectorplotterscan, in
theory,be programmedto act as rasterplotters,thoughoperationallythis maynot be successful.
It is neithertheoreticallynor practicallypossibleto use rasterplottersas vectorones.
Most plottermanufacturers
provideplottingpackageswhichthe usercan incorporatein his
computerprogramsto drive the plotter in simple fashions.Many such packagesinclude the
facilityto drawup to 50 or so specialsymbolsbut, to go beyondpoint symboland simpleline
plotting and plot re-scaling,the user generallyhas to providethe bulk of his own computer
softwareunlessit can be obtainedthrougha softwareexchangescheme(such as the Geographic
ProgramExchangebased in MichiganState University).A good exampleof the variationsin
graphicformwhicharefeasiblein a computer-basedsystemwherethe datastorageanddepiction
arenot inextricablylinkedandwherespecialpurposesoftwarehasbeenwrittenis in the depiction
of surfacesby Brassel,Little and Peuker(I974), Batson,Edwardand Eliason(I975) and Yoeli
(1976).They haveproducedcontoured,inclinedcontour,Tanaka-style,slopevector,hill-shaded
andotherformsof surfaceportrayal.Currently,someof thesedemandexoticandrarelyavailable
equipment,but standardcontouringis now a frequentlyused and simpletechnique(see Fig. 5).
90
DAVID
RHIND
o
o
3
411
104500m
GEOGRAPILCII
,S\E
FORMAT
\
c~\(jaragei'
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It
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144
ellemoor Inn
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FIGURE 7.
OOR ROAD
..".- .-
.
\29.3m
. BM 29.52m
High quality linework from Ordnance Survey i: 1250 scale plan SU 4114 SW plotted using a Ferranti
age of data which are only related indirectly to geography. The objection may be pedantry, but
the term describes a rapidly growing field of interest, stemming from the late 1960s and early
1970s, which saw a rapid growth in the computer-based informationsystem business. The primary
customers were and remain local administrative authorities and large commercial and manufacturing firms, which typically have the requirement to handle large volumes of data at a very
disaggregated level and are able to assess and/or update any part of this quickly and efficiently.
The environmental equivalent of this development was the growth in popularity of the environmental inventory; the business/computing-type approach to such inventories was epitomized by
the creation circa 1962 of the Canada Land Inventory and its technical arm, the Canadian
Geographic Information System (C.G.I.S.; see Switzer, 1975). Academic interest in the field in
Computer-aided
cartography
FIGURE 8.
9I
High-quality output from World Data Bank II plotted using a Gerber plotter with photohead (provided
by the Central Intelligence Agency)
the United Kingdom was minimal until circa I970, with the formation of B.U.R.I.S.A., a British
version of the Urban and Regional Information Systems Association. The most significant
overall formal step in the involvement of academic geographers in the geographical information
system field was the formation of the commission on 'Geographical Data Sensing and Processing'
of the International Geographical Union. The success of this commission is evidenced by their
influential publications (Tomlinson, I97I; I.G.U., 1972; Tomlinson, Calkins and Marble, 1976;
I.G.U., I977) and the large grants given by state and federal agencies in the United States to
the Commission for the investigation of information systems for land-use planning and for the
reviewof data-basedevelopmentsin the U.S. GeologicalSurvey.
The implicationsof all this for automatedcartographyare very substantialindeed, since
those individuals involved in the use of the spatially referenced data bases have long since begun
to make maps in increasingly large numbers. Though production of lineprinter maps is very
92
DAVID. RHIND
common from such systems, the maps produced from this source have never been restricted to
the low-quality type: C.G.I.S. was designed from the outset to cope with input from highresolution maps and the facility for output of answers in moderate and high-quality map form
was soon added.
Several distinctly different lines of development can be discerned in work to date. One of the
earliest and computationally simplest methods (see Boehm, I967; I.G.U., I972) was to store data
for spot locations or for fixed-size and fixed-shape areas. Examples of information systems based
on single point locations are the property centroid-based Joint Information System for TyneWear County (N.G.P.S., 975) which contains 600o000 land-use records, and the similar, if
smaller, Durham Land Use Survey System. In the Minnesota Land Management System (Hsu,
Kozar, Orning and Street, 1975), grid cells (in reality, the 40-acre parcel) were used as the basis
for data storage because this is the 'atomic structure' of Minnesota's landscape, it is the basis on
which many governmental records at county, regional, state and federal levels are based and
because it also lends itself to computer mapping. The New York State Land Use and Natural
Resources System stores land use and topographic data by i-km squares. Similarly, Duffield and
Coppock (I975) have built a system which uses 5 km and i km square-based data for Scotland
and use this to produce maps of the output from combined logical, arithmetic and geographic
searches on several variables: 'map all the locations with more than 50 empty hotel beds in
August within 5 km of water more than 5 km2 in extent' is the form of request which would
normally be serviced. Perhaps the largest grid-based data set extant, other than the LANDSAT
satellite output, is the I50 ooo record by I67I variable Great Britain I97I Census of Population
(the data are also made available by Enumeration District areas). The creation of an information
system to handle this, involving the compaction of the data into one-tenth of its original volume
and speeding the access to the whole data set by a factor of thirty over the standard procedures,
has made access to any part of the data possible within a few seconds on an on-line system and,
as a result, has made possible the production of a large variety of computer maps. A more
sophisticated system operating with variable-size grid squares is the ORRMIS system, devised
at the Oak Ridge National Laboratory (Tomlinson, Calkins and Marble, 1976). LINMAP, a
United Kingdom government-created Geographical Information System designed to produce
statistics and point symbol, zone and grid maps after retrieval and combination of data from
various government sources, has been in use since about I973 and has been described by Gaits
(1974, I975). In that time it has been used to produce over Iooo maps.
A distinctly different line of development includes schemes such as the PIOS system
(Dangermond, 1972; Tomlinson, Calkins and Marble, I976), GIMMS (Waugh, I974) and
NIMS (B.U.R.I.S.A., I976), which are often segment-based systems. In the latter, street or
other physical and conceptual boundaries are assembled in chains to create networks or zones.
The most widely used segment-based scheme is undoubtedly the Dual Independent Map
Encoded-or DIME-file, originated by the U.S. Bureau of Census (U.S. Bureau of Census,
I970), even though the original DIME file did not permit the segments to be other than straight
lines. While much more demanding to collect than are point-or grid cell-referenced data, these
facilities do provide the possibility of some automated data quality checking (Aangeenburg,
I975), which is virtually impossible in point-referenced files. Availability of such zonal outlines
permits the simple automation of choropleth mapping: perhaps the most striking cartography
yet produced from such files is that by the U.S. Bureau of Census (Meyer, Broome and Schweitzer,
I975) in the 65 atlases of those Standard Metropolitan Statistical Areas with a population over
500 ooo in 1970. To produce these, 5000 colour separations for 780 maps were produced in a
14-month period.
It has been pointed out in a previous section and emphasized above that the variations in
Computer-aided
cartography
93
sophisticationof the spatialreferencehave significanteffects upon the final map form. In an
informationsystemcontext, however,the manipulativeoperationswhich it is possibleto carry
out (Tomlinson,I974; Rhind, I975b, 1976)partiallydeterminethe map contentand these are
criticallyrelatedto the organizationof the data elementsand their implicit and explicit cross
references.Peukerand Chrisman(1975) have suggestedthat most existing cartographicdata
files are input-related,i.e. their organizationis a reflectionof how the data were digitizedor
otherwisecreated.In addition,they emphasizedthatcomparativelyfew attemptshavebeenmade
to link geographicaldatafiles together(but see U.S.G.S., 1975): as a result,quantitativecomparisonsof the relationship,say, betweengeologyand soils (Tobler, I975) is extremelydifficult.
Finally, Peukerand Chrisman(1975) pointed out that most data structuresused to date for
cartographicfiles only includetopologyin an implicitway. There is now widespreadrecognition
of the necessityfor inclusionin files of what they summarizeby 'flexibility,comparabilityand
topology':a good exampleof the effectsof the lack of these in an initialsystemis the difficulty
in use of the OrdnanceSurvey digital map data (Atkeyand Gibson, 1975). In this, datawere
initiallystoredmoreor less as theycameoff the digitizingmachine,in a waydesignedto simplify
the re-drawingof existing-typemaps.One majordisadvantageof this methodof storageis that
it is impossiblesimply to generatefunctionalunits such as properties,since a house frontage
is storedas somepartof the side of a streetwhileotherpartsof the boundaryof the sameproperty
are not relatedto each other in any explicit way and are usuallyscatteredthroughoutthe file.
The startof a majorproject,which is intendedto producethe meansfor softwarereorganization
of the dataas required,was largelybroughtaboutin I975 by the inabilityof potentialusers to
relate their own data to that of the OrdnanceSurvey and thus save themselvesdigitizingthe
same boundariesas those providedby the nationalsurveyorganization.
It shouldbe appreciated,however,that the requirementto carryout manydifferentoperations with cartographicdataensuresthat the dataorganizationwill be extremelycomplex.The
examplegiven in Rhind (1976), which containsa vast miscellanyof pointersto permit direct
access to individualand relateddata elementsin an extremelysimple map, is not an atypical
structure.In addition,the use of such cartographicor geometricdata for logicalor arithmetic
taskssuch as polygonoverlaynecessitatesratherhigherstandardsof dataqualitythanhavebeen
necessaryfor such mappingin the past:it is quiteone thingto fill in missingsectionsof a plotterdrawnline by handbut quite anotherto computeareasif some partof the boundaryis missing.
In some cases, therefore,the data accuracyrequirementsdifferfor cartographicand analytical
purposes.
CONCLUSIONS
The developmentof automationin cartographyhas largelyfollowedtwo differentcoursesuntil
recently,relatedto the involvementof researchworkers,such as geographersand (more often)
earth- and social-scientistson the one hand, and 'topographiccartographers'
on the other. In
essence, all the substantialand solvableconceptualproblemsin map makinghave been solved
throughthe individualefforts of these groups, though not all of the solutionshave yet been
documentedand the pre-displayoperationsof generalizationand surfacegenerationwill remain
problemssince they are under-defined.The multiplicityof world-widedevelopmentsin the
field suggest that any type of map extant can now be producedby makinguse of a computer,
thoughthe sensibledegreeof involvementof the machinewill dependon local facilities,labour
availability,economicsand the time-scaleof the project.The most obviouspresentbenefitsof
automationcome when the dataare alreadyin digitalformand when largenumbersof similarstyle mapsarerequiredor whereprogressiveup-datingis to be carriedout. However,the growing
availabilityof both 'topographic'and 'thematic'datain digitalformand of appropriatesoftware
DAVID RHIND
94
and hardware suggests that user interaction with the map form and personalized production of
maps will grow in importance.
The next major benefit of involving the computer in the production of maps, however, is
likely to come through the increasing use of sophisticated data-base management techniques to
obviate redundancies in the data set and to link different and hitherto incompatible data sets
together so that derived variables can be mapped and analysed. The latter is far from an easy
task, particularly in the United Kingdom where different data sets are collected over areas of
many different sizes and shapes. But economic pressures are already forcing the 'topographic
cartographers'to find other users for their data while, at the same time, academics and government 'thematic cartographers' are beginning to appreciate the potential of readily available
digital maps for linking with their own data or for use merely as a backdrop to them. An ironic
form of this co-operation is the use by numerous geographers(and others) of the C.I.A.-produced
World Data Bank I (Robe in A.C.S.M., 1976, pp. 152-62) and the eager anticipation of the
much more detailed country boundaries, rivers and railways in World Data Bank II (Fig. 8).
For these reasons, and in this one respect, the gulf between the research and the professional
cartographic cultures seems now to be diminishing.
ACKNOWLEDGEMENTS
Thanks are due to the Central Intelligence Agency, Ordnance Survey, Dr S. M. Scarrett and Mr T. C. Waugh for
kindly providing some of the illustrations. Mrs J. Dresser typed all the drafts of the paper.
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