ML17321A661
| ML17321A661 | |
| Person / Time | |
|---|---|
| Site: | Cook  |
| Issue date: | 10/31/1980 |
| From: | ECKERT S, WOODS D D WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP. |
| To: | |
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| ML17321A660 | List: |
| References | |
| NUDOCS 8506100410 | |
| Download: ML17321A661 (34) | |
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HAN-HACHINEINTERFACEDESIGNBASISDOCUHENT:INFORHATIONCODINGFORCOHPUTERDISPLAYSYSTEMSREV.0P.D.MoodsSS.EckertOctober,1980g506i004io850581PDRADOCH05000Si 0ltl SummaryIntroductionCharacteristicsofaGoodCodeCodingFunctionsCodescanaidsearchprocessCodescanamplifyinformationCodescanorganizedispersed,informationCodescanaidinformationreductionCodingDimensionsSymbologyAlphanumericSizeLineStructureBrightnessHighlighting OrientationBlinkTime-varyingcodesAuditoryCodesColorColorCodingStrengthsCautionsAssociatedwithColorCodingColorCodeAl,phabetSizeRecommendedApproachtoColorCodingInteractiveTechniquesCandidatesforCodinginProcessControlReferences 2.0IntroductionThisdocument,sponsoredbytheControlRoomandComputerDevelopmentgroupoftheStrategicOperationsDivision,presentsHumanFactorscriteriaforthedevelopmentofinformationcodingschemesincomputerdisplaysystems.
0 Informationdisplaysystemsshouldsupportaquickandaccuratetransferofinformationtotheuser.Codinginformationisonetechniqueavailabletothedesignertomeetthisgoal.Codingmethodsshouldbeincorporatedwhenanyofthefollowingthreeconditionsareapplicable:~whenadensepresentationofinformationisrequired~whenthetaskrequirementsaredifficultorprecisewhenaquickresponsetimeisessentialCodingtechniquesshouldbeviewedasoneoptionamongmanytofacilitateinformationprocessingandinterpretation.Thearrangementof"theinformationandthemodeofpresentationwillhavedramaticimpactsoninformationtransfer.Onecannotincorporatecodingintobadlyformatteddisplaysandexpectdramaticoperationalimprovements.Therefore.codingshouldbeoneofthelastelementsdisplaydesign-thebestformatshouldbedevelopedforpresentingtheinformationtotheoperatorpriortoincludingthecodingfeatures.Characte'risticsofaGoodCodeDetectability-Anystimulususedinthecodingofinformationmustbedetectableorperceivablebytheuser.Discriminability(1)Theusermustbeabletodiscriminatebetweendifferentcodingtechniques;(2)withinagivencodingmodality,theusermustbeabletodiscriminatedifferentvaluesorstates.Thenumberofdiscriminablestimuliwithinacodingdimensionchangesacrossdimensionsandofthetypeoftask-eitherare]ativeoranabsolutediscrimination.
Aperson'sabilitytodetectdifferencesbetweenstimuli(tomakearelativejudgement)ismuchkeenerthanone'sabilitytodetectadifferencewitharememberedcomparison.Introducingreferencepointssuchasperceptualanchorscanincreasetheeffectiveresolutionwithinacodingclassbyallowingrelativejudgements.~Compatibility-Thecodechosenshouldbecompatiblewiththetypeofdataorinformationbeingcoded.Thusaqualitivecode(symbols,color)shouldbeusedforqualitivedata;aquantitativecodinotechnique(length,intensity,size)isbetterforpresentingquantitativeinformation.'Forexample,colorcouldbeusedtocodeaquantitativedimensionsuchastemperatureasinaninfraredphotograph.Thisisagoodwaytorepresentdifferencesintemperature.However,'hisisapoorwaytoindicatetemperaturevaluessincethereisnoobviousrelationshipbetweencolorandquantity.Mhenthevalueofadatapointrepresentedbygreendoubles,whatcolorshouldresult?oAssociation-Symbolcodesshouldphysicallyrepresenttheactualobjectbeingportrayed.~Standardization-Theuseofcodesshouldbestandardizedthrouahoutthedisplaysystemandthesurroundinguserworkstation.Ifredisusedasanalarmcolorintheindicatorlightsaboutthecontrolstation,redshould.alsobereservedasanalarmcolorontheCRTdisplaysifatallpossible.
~Redundancy-Itisadvantageoustouseredundantcoding:twoormorecodingdimensionsareusedincombinationtodesignateaparticularcondition.~Inaddition,acodeshouldnotintroducefatiguingordistractingeffects',anditshouldberelativelyeasytoincorporateintothemachinesystem.Iftheseguidelinesaremet,thecodingschemeadoptedshouldbeeasytointerpretwithlittleintercodeconfusion.CodingFunctions1.CodescanaidsearchrocessThetimetosearchasetofcandidatesforaparticulartargetincreasesassetsizeincreases.(Steinberg).Thereforesearchtasksbecomemoredifficult(takelongerandaremoreerrororone)astheinformationdensityofadisplayincreases.Codescanincreasesearchspeedandaccuracythroughacategoryeffect.Mhenthetargetisamemberofclearlydefinedsubsetofthetotaldisplay,searchspeedahdaccuracvisafunctiononlyofsubset"sizenotofthetotalnumberofdisplayelements(Egeth,Jonides,and6NMall,1872).Thisistrueaslongasthenumberofdifferentsubsetsorcategoriesissmall(lessthan4).Forexample,searchingforaredtargetamonga'fewredandmanywhitedisplayelementsisfasterandmoreaccuratethansearchingforthesametargetwhenalldisplayelementsaremonochromatic.In.general,itemsofagivencategoryaredetectedfasterandmoreaccuratelyagainstabackgroundconsistingofitemsfromadifferent
categoryascomparedtoabackgroundofitemsfromthesamecateaory(Oeutsch,1977).2.Codescanamlifinformation.Codesfulfillahighlightingfunctionbyattractingtheuser'sattentiontoimportantinformation.Forexample,codes,canbeusedtoemphasizeanomalies.andabnormalstates.3.Codescanoranizedisersedinformation.Codingtechniquesareparticularlyvaluabletointegrateinformationthatisspreadacrossthedisplaypageasopposedtoinformationthatisalreadyorganizedby'rows,columns,orquadrants.4.Codescanaidinformationreducti'onAflexible.displayshouldfacilitateseveraltypesofviewingtasks;whatisrelevanttoonetaskmaynotberelevanttoanother.Theusermayberequiredtoblockoutinformationthatisnotper-tinanttothetaskathand.Displaysshouldbestructuredsothatinformationreductionisagatingtaskratherthanacondensationtask.Gatingrequiresonlythattheuserignoreirrelevantstimulusdimensions.Thisactivityispartofnormalandoftenautomaticperceptualmechanismsthatthebrainroutinelyusestopreventinformationoverload.Condensationtasksplaceaburdenontheuser'scognitivecapacitysincetheinformationmustbecombinedincomplicatedways{Norse,1979;Posner,1964).
Forexample,redtrianglesandbluesquaresmayhavetobementallygroupedtogetherandtreateddifferentlyfromagroupofredsquaresandbluetriangles.Anotherwaytoaidinformationreductionistostructuredisplaysintoforegroundandbackground.Thisapproachtakesadvantageofautomaticperceptualprocesseswhichdifferentiatefigurefromground.Whenimportantandunimportantorreferenceinformation(forexamole,scalesorgridpatterns)isundistingushed,theusermaysufferfrominformationoverloadorhemayberequiredtouseupmentalcapacityinordertodistinguishtheprioritylevel.Justasaninformationhierarchysupplieslayersofinformationfromthegeneraltothdetailed,individualdisplaysshouldprovidelayersofinformationgoingfromreferenceorbackgroundtoimportanttocriticalinform-ation.Notethatinformationreductiontechniquesareonemeansforkeepingdisplaydensitywithintheoptimumrange.Inorderforthedisplaydesignertomatchhiscodeselectionandanoverallcodingschemetotheuser'stasks,hemustdeterminewhat1informationtheuserneedstoextractfromeachdisplay.'hiscanbeaccomplishedthroughataskanalysiswhichdeterminestheuseractivitieseachdisplaymustsupport.CodingDimensionsSymbology(Shape).Graphicorpictorialsymbolsandshapesasdataidentifiers.Symbolsshouldrepresenttheobjectbeingportrayed.Thisiscallediconiccodinganditreducestrainingtimeascomparedtoarbitrarysymbolcodes.,Iconiccodingalsoheightenssymbolrecoqnitionandstrenqthenstheassociationbetweenthesymbolandtheactualobject.
Thiseffectincreasesthetransparencyoftheinterface.Symbolsshouldbesimplebutdetailedenoughtobediscriminableandtopromptassociationsandaccurateidentification.Thenumberofshapesthatcanbecorrectlyidentifiedisquitelarge,limitedprimarilybytheabilityofanobservertoassociatethesymbolswiththecorrespondingobjects.Thisabilityisdependentuoonthefidelityofthesymbolshape,usertraining,andstress(Oda,1977).Generallyamaximumof10to15differentsymbolsarerecommendedformostapplications.2.AlphanumericAlphanumericcodingisfrequentlyusedtopresentquantitativeinformation,tagnumbersorsimilaridentifiers.Anyabbreviationsoracronymnsshouldbereadilyassociatedwiththetotalword,andtheyshouldbestandardizedthroughoutthesystem(bothonthecontrolpanelandonallCRTdisplaypages).Alphanumericsshouldideallybethreecharactersorlessbecauseofthepropensityofoperators.Tominimizetransoositionerrorsinidentifierssuchasiagnumbers,alphabeticcharactersorotherseperatorsshouldbeinterspersedamonglongrunsofdigits.3.SizeTheactualsizeofacharacterorsymbolcanbevariedtoconveyinformationtotheuser.Anoperatorcandifferentiatebetweenapproximatelyfourorfivedifferentsizevariationsonanabsolutebasis.However,formostapplications,twosizeoptionsarere-comnended,enablingausertoreadilydiscriminateandidentifythesizebeingpresented.Logarith<<c.(constantratio)sizevariationsaremoreaccuratelydifferentiatedthanlinear.
Sizecodingisbestusedtodifferentiatebetweeninformationofdifferingimportanceorsymbols/componentsindifferingstates(i.e.,onoroff).Onedrawbackofsizecodingisthelargerspacerequirementstopresenttheinformation.4.LineStructure.Varyinglinestructurescanbeusedtoconveydifferentmessagestotheuser.guantitativeinformationcanbecoamunicatedbvvaryingthelengthorthewidthoftheline.gualitativeinformationcanbeconveyedbychangingthetextureoftheline(solidvsdashedvsdotted).Linestructurecodingcanbeeffectivelyusedongraphicdisplaypresentationssuchasmimicdisplaystodifferentiatebetweenflowandnoflowstatesforthefluidorelectricalcurrentlinesofthediagram.Alinestructurecodecanbeexpandedintoatexturecode.Textureworkswellasacodeforlargefieldssuchasareasonagraphortoindicatestatesonlargesymb'ols.5.Brightness/ItensityManyCRTsystemshavemultiplelevelsofintensitywhichcanbeusedindisplaycoding.Ingeneraltwolevelsofintensityarerecomnendedfordisplaycoding.Theeffectivenessofbrightnessasacodingmethodisdependentuponthecontrastofthedimmerlevel.Ifthiscontrastispoor,fatiguemayresultandinformationmaybeoverlooked.Ifthecontrastofthelow-intensityoptionisadequate,brightnesscodingcanbeprofitablyusedtosuppressback-groundorlessimportantinformation,likegridlinesandlabels, whichareonlyinfrequentlyrequiredbytheexperienceduser.6.HighlightingMonochromaticdisplaysprovidesomestandardhighliqhtingtechniqueswhichcanbeusedtodesignateimportantinformationonadisplayorattractausertoachangeofstaterequiringhisattention.Underlininqorunderscoringarecommonlyavailableforhighlightinginformation.Videoreverseisaneffectivetooltoattractanoperator'sattentiontoanimportantpieceofinformation.Specialsymbolscanbeusedtodesignateimportantinformation(i.e.arrowsorbullets);Criticaldata.valuescanhaveboxesorcirclescircumscribedaroundthemtohighlightthemtotheuser.Allofthesemethodsofhighlightingandattention-gettinqfacilitateuserinterpretationofhighdensity,complexdisplaypresentations.7.OrientationTheangularorientationofasymbolorlinecanbevariedto.conveyinformationtotheuser,forexampleclocksanddials.Orientationisasuitablecodingtechniqueaslongasonlyrelativediscriminationsarerequired.Errorratesforabsoluteidentificationofanglearehighformorethanafewcategories.8.FlashRateorBlinkCodingBlinkcodingisaneffectiveattentiongettingtool.Howeverblinkingamessagereducesitsreadability(flashinganadjacentsymbolcansolvethisproblem).Blinkingalsotendstobeveryfatiguingandannoyingtousers.Thereforeblinkcodingshould/onlybeusedtocalltheuser'sattentiontocriticalevents.Flashratesshouldbebetween1and5Hz(3Hzisatypicalrecommendation)andonlyonerateshouldbeused.Becauseofthedrawbackstoblink'I coding,eventacknowledgeorblinksuppressionshouldbequicklyavailabletotheuser.9.Time-varyingcodesAnimationisapowerfulwaytodisplaytime-varyingdata.Insteadofrepresentingtimewithaspatialdimensiononagraph,simulationtimecanbeusedtoencoderealtime.Fasttime,slowmotionandfreezeframetechniquescanhighlightinformationthatwouldotherwisebe'difficultfortheusertoprocess.Howeverthedesignermustbecarefulherebecausechangesintimeframecanalsodistorttherealtimeinformation.Anotherexampleoftimecodesis'displayaidingwhichshowsatrailofdisplacementsthatfadeovertime,sothatamovingobjectorachangingdatapointleavesatrailoffadingfootprintswhichindicatesitspositionorvalueintherecentpast.Notethatthisexamplecombinesbrightnesscodingwithatimecodeto'communicatetrendinformationtotheuser.Thecriticalvariablefortime-varyingdisplaysisthedurationoftheblankintervalbetweenframes.Notimegapisbestandifthegapexceeds1second,memoryaidingmaybenecessarytoprovidecontinuity.10.AuditorycodesTheauditorymodalityisusuallyunderestimatedasacodingmedium.However,severaldimensionsofsoundsareavailabletoconveyinformationtotheuserinaneffectiveway(frequency,itensity,quality,pattern,rhythm).Theearpossessestremendouspowersoftemperalresolution(Green,1978).Auditorycodesshouldtakead-vantageoftheseabilities.
Becauseauditorycodesareusuallyusedaswarningsignals,amoredetaileddiscussionofauditorycodingtechniqueswillbereservedforaseparatereportonHumanEngineeringcriteriaforalarmandannuciationsystems.11.ColorColorisnottheultimateanswertoallcodingproblems.Colorshouldnotbeusedtotheexclusionofachromaticcodingmethods,rathertheyshould.beusedtosupplementandcomplementoneanother.ColorCodingStrengths~Colorcanincreasedetectionaccuracyandsneedbyreducingthesizeofthesettobesearched.Thisistrueonlywhenlessthan4colorsoccuronanygivendisplay.-Forlargeralphabetsizes,colorcodingcanactuallyincreasesearchtimes(Christ,1975).Colorisagoodattentionfocuserwhenusedjudiciously.Theutilityofcolorcodingforhigliohtinginformationisenhancedwhenthereareonlyafewcolorspresentedonthedisplaysothatachangeincolorfromanormalconditiontoahighlightedconditionwillbereadilydetectable.Colorisaneffectivetoolforintegratingphysicallyseparatepieces,ofdata.Colorcodeddisperseddatacaneasilybyorganizedintoasingleperceptualunitforfurtheranalysisasagroup.~Colorcanbeusedtoseparatedisplaysintofigureandgoundareas.
oColorisaneffectivemeansofinformationreductionbyseoaratingforegroundandreferenceinformation.Sidorsky(1979)foundthatcolorwasofvalueprimarilyforgroupingdataatafirstlevelofanalysis,i.e.theinitialgroupingofwhichdatapiecesarerelatedtowhich.HoweverSidorskyfoundcolorwasnobetterandperhapsworsethanshapeoralnhnumericcodingforsubsequentlevelsofanalysis.Therefore,colorcodingcanbeeffectivelyusedtostructuredisplayedinformationforsubsequentanalysisandinterpretation.Colorcodingcanbeusedtoenhancenaturalrepresentations.Insomeapplicationscoloristhemostdesirablecodingmodalitybecauseitmostnaturallyrepresentsthephysicalrealitybein@encoded.Forexample,thered/yellow/greencolorassignment"aremostnaturallyassociatedwithdanger/caution/normaldesignationsthanother,achromaticcodingdimensions.Colordisplaysareoftensubjectivelvoreferredovercorn"letel:achromaticdisplays(Grist,1975;Chase,1970;Schutz,1961).Colorbackgroundsaswellascolorsy..bnlscanLeusedtoco"einformation.Forexample,changingthebackgroundfrom.blacktodarkbluecouldbeusedtoindicatechangesinplantorsystemmode.However,displaysshouldbeevaluatedwiththecolor,backgroundbecauseofpossibleflickereffectswhichincreaseasfieldsizeincreasesandbecauseofpossiblecontrasteffectsonlegibility.
~~CautionsAssociatedwithColorCodinq~AbnormalColorVision?tisestimatedthat8Xofthemalesand0.4".ofthefemalepopulationposssssomeformofabnormalcolorvision.Themostcommonformofcolordeficiencyi'saromaloustrichromat',smwhe~eapersonissensitivetothreechromaticstimulibutthei.matchesdonotfallwithin'henormalrangeofvar',ation.Themo.tcordondeficiencyentails.aweakgreenresponse(deuteraro"..aly)whichaccountsfor4.9Xofthemalesand0.38Kofthefemales.Aweakredresponse(protaronaly)accountsforanother1,;ofthe~alepopulation.potentialsolutiorsincludescreening'usersbycolordeficienciesandchoosin".choosingcolorswhicharenotaffectedbvthemorecomonformsofabnormalcolorvision.~HardCoInapplicationswherehardcopiesofdisplaysarerequired,allcolorcodingmustbusedredundantlywithmonochromatictechnioues.DeceasedRsolutionDisplayresolutioncanbereducedoncolorCRTsbecauseoftherequirementtoplacethreephosphordotsofdifferentcolorsonthedisplayface.Tocompensateforthis,characterandsrm'-olsizesmustbeincreasedtoaccuratelyconveycolorinformationtotheuser.MisreistrationTheneedtoalign-3beamscancausemisregistrationproblems.Periodicadjustmentswillberequired.
~~No<seCode.Theveryfactorswhichcontributetocolor'seffectivenessasacodemakeitarealnuisanceandhinderancetotheuserifnotaporop-riatelyused.Whennotusedjudiciously,colorcodingcan,infact,degradeperformance.SoectialSensitivit!Functio.".s.Theey~isnotequallysensitivetoal';w<svelengt"s(s";e."i"ure1).Thismar<sthatdiff::r=-ntcolorso<idnticalpiyicalirt.=nsii."swillnotappearequallybright.Whenavarietyofcoloursareus.dinthesampictur,therelativeintensitylev.lofthv.riouscoloursshouldbeinaccordancewiththespectralsensitivitvo.theeyeinordrtoavoidunintendddominanceofonekindofinformationoveranothr.
.However,notethatthesebrightne'sscuesasafunctionofwavelengthcanbeusedbycolor-d~ficientindividualstodistinguishdifferentcolors.Colorhotoicvision)encetionhasahiherthresholdthanachromatic(scotoicvision)ercetion.Perceivedcolorswillchangeandmaybecomeachromaticifthedisplayintensityistoolow.Thismeansthathighersymbolandcharacterluminanceisrequiredforcolordisplaysthanachromaticones.Ambient?11uminationReuirements.ColorCRTsaregenerallymoresensitivetoambientillumination.ContrastorluminanceareusuallylessforcolorversusmonochromaticCRTsandcorrespondingdecreasesintheintensityofambientilluminationmayberequired.ThecoloroftheambientilluminationcanalsodramaticallyeffecttheperceivedcolorofaCRT.Theselectionofcolorsforinformationcodingshouldbemadeinasituationwhichstimulatesboththecolora'ndintensityoftheanticipatedambient'illuminationintheoperationalsetting.ColorContrast.Whencolordisplaysareviewedforlongtimeperiodsapparenthueandsaturationcanchangeduetocontrasteffects.Thevisualsystemprocessescolorinformationinopponentpairs:red-green,blue-yellowandblack-white.Prolongedviewingofonecolorreducestheeye'ssensitivitytothatcolorandincreasestheeye'ssensitivitytothecomplementarycolor.Simultaneouscontrasteffectscanalsoproducechangesinperceivedcolorsduetotheinfluenceofthecolorofsurroundingareas.Contrasteffectswillbemostpronouncedwhen h
~~therearelarge,coloredfieldsonthedisplays.~ChromaticAberration.Thelensoftheeyefocuseslightordifferentwavelengthsatjdifferentdepths.Thisiscalledchromaticaberration.Iftherearemanydifferentwavelengthcolorsonagivendisplay,theeyecannotfocusallofthecolorsatthesametime.Theaccomodation(focusinq)mechanismswillcontinuallyadjustinordertoattempttomaintainproperfocus.Thiseffectisonemajorsourceofeyefatigue.Totheextentpossible,colorsofverydifferentwavelengthsshouldbeavoidedindisplaysthatwillbeviewedforlongperiodsoftime.ThisproblemisthereasonHumanFactorsguidelinesoftenrecommendminiraluseofbluecolors.ContrastRatioContrastratioisnotindependentofforegroundandbackgroundcolors.Figure/groundcolorrelationshipscanincreasetheeffectivecontrastratioandtherebyincreaselegibility.Howeverapoorchoiceofcolorscandestroyvisibility;forexample,darkblueonablackgroundisvirtuallyinvisible.Theremaybetimeswhenlessvisiblesymbolscanbeuseful.Forexample,softwareconsiderationsmayrequirethatacertainsymbolmarkeachtabpointonadisplay.Choosingapoorlyvisiblesymbolcolorcaneffectivelygateoutthisirreleventinformation.
s~~~Tes~troons.d~~i;alas.BecauseofillcAnation,luminance,contrasteffectsandchromaticaberrationitisessentialthatproposeddisplaysbetestedontheactualdisplaymedium,i.e.ontheCRTchosenfortheaoplication,intheappropriateenvironment.ThereisnoreasonthatacoloreddrawinqofproooseddisolayswillcorresoondatalltotheactualCRTdis-lay:.AC~Tdisplayisalihte~i'.terandadrawn,"i"sa4"hrf!e=t'r.t:letWOCaSs'SdOnOtnrOduCeperC=ptiOnSt;:ataieautOnatiCasl"equ-'.al~-t.0herComments.Ifsinglefailurecriteriaareimnortant,cZeosingcolorsbasedonibea;.scani~creaserdurdancy.Howev=-rcult-;p'e'"earncolo:s,p=rticusarl"w'.".ite,increasecon:erqencsp.o~le~s"-hichdecreaseI."-effectivecontrastofthdisplay."olorC".d=Ap,a.e-.Siz:-.h"r"i.-ata~d".ncyfordis"l~y".e"i-nerst~u"-e"o"ero'.orsthorn'soprationallyw:rrant;".d.D:s'ig.".ers;.hcu:d:o-.f::e:cm-elledtutilizedallofthecolorsthatagivenCRTprovides.Thenumberofcolorsthatcanbediscriminatdaccuratelydependson'avelen~t.".,saturation,bri~htness,illumination,symbolsizeandcontrasteffects.Whilehundredsofcolorscanbediscriminatedonarelativebasis,Haeusin."(1976)foundthatonly4colorsworereliablydiscr'.min-t:donanabsolutebasisusingtestdisplaysthataretypicalofcurrentCRTdisplays.
Becauseofthisresultandbecauseofthecautionnotedintheprevioussection,thecolorcodealphabetshouldnotexceed3or4hues(MyszeckiandStiles,1967;Burdicketal,1965).RecomnendedApproachtoColorCodingTherearemanycodingschemeswhichcanmeetHumanFactorscriteria.Thefollowingisonegeneralapproachthatfulfillsthesecriteria.Colorshouldbeusedtoorganizedisplaysandfocustheuser'sattentiononimportantinformation.Ananalogycanbemadebetweenlevelsofaninformationhierarchyandlevelsofacolorcode.Aninformationhierarchyaidstheoperatortoseparatereleventfromlessreleventinformationbyprovidingdisplaysofdifferentlevelsofdetail.Acolorcodeshouldhelptheuserseparateimportantfromunimportantinformationbyprovidingdifferentlevelsoforganizationwithineachdisplay.1.Referenceorbackroundcolor..Thiscolorshouldbeclearlyvisiblebutsubdued.Itshouldnotbethemostsalientcolor(i.e.notthebrightestcolorortheonewiththebestcontrast)availableontheCRT.Staticorreferencematerialshouldmakeupthiscategory.2.For'eroundcolor.Thiscolorshouldbethemostsalient(brightest,rbestcontrast)coloravailable.Thiscategoryshouldincludedynamic,importantinformation,informationthatisnecessarytofulfillthetasksthedisplayisdesignedtosupport.
3;Hihlihtcolors(upto2colors.Thesecolorsshouldclearlydemandtheuser'sattentionforexample,redforalarminformation.Thiscategoryshouldcontaintheleastnumberofitems,only3or4perpage.Ifthisisexceededthecolorwillnolongerfulfillitsattentiongettingfunction.Thisschemaorganizestheinformationonapageintolayers-almostaddingadepthdimensionontothepage.(Actuallyperceptual-researchshowsthatfiguresdotendtostandoutondepthinfrontoftheground;Coren,1976).Thepyramidoflayersfocusestheuser'sattentiondirectlyontoimportant(foreground)andcritical(highlighted)information.Withineachcodinglevel,dispersedinformationisorganizedintoasingleunit.Thisapproachcanbeexpandedtoothercodingtechniquesaswell.Forexample,achromatichighlightingtechniquescouldbeusedand2levelsofbrightnesscouldrepresenttheforegroundandreferenceinformationlevels.Howeverthereshouldbeaceilingof4codinglevels.Thecodingschemepresentedherefulfillseachofthecodingfunctionsdescribedearlierinasystematicway.Searchperformanceisenhancedsinceinformationiscategorizedatanoptimumlevel(3or4categories).Criticalinformationstandsoutthroughthepyramidstructureandeachcolorlevelpullstogetherdispersedbutrelatedinformation.Thecodinglevelsaidinformationreductionbyorganizinginformationaccordingtoprioritylevels.'inallyittakesadvantaoeoftheuser'sperceptualandattentionalmechanisms.
HumanFactorsreconmendationsoncodingusuallyprovideanannotatedlistofeightcolors(theeightcolorsusuallyavailableonCRTsystems).Eachcolorismatchedasbestsuitedfordifferenttypesofinformation.NosuchlistisprovidedherebecauseitencouragestheoveruseofcolorcodingandbecausetheappropriatecolorsforeachapplicationshouldbedeterminedbytesttrialswiththeactualCRT,displaysandvisualenvironment.-InteractiveTechniues.Codingtechniquesarenottheonlymeansavailabletofacilitateoperatorprocessingandinterpretationofcomplexdisplays.Interactivecapabilitiescanbeincorporatedintothesystemtoenableuserstoseparatereleventfromirreleventinformation.OnsomeCRTsystems,multiplegraphicplanescanbeutilizedfordifferentgroupsofinformationsothatanoperatorcansuppressorrequestinformationasrequired.Gridlines,labels,units,scales,andlimitsareallcandidatesforsuppressionbyanexperiencedoperator.Anoperator,.shouldalsobeabletointeractivelyrequestsupplementalinformationthatdoesnotwarrantcontinuousdisplay.Forexample,onagraohicaldisplay,anoperatorcouldrequestadigitaldisplayofactualorhistoricalparametervalues.Interactivetechniquescaribeeffectivelyusedinadditiontocodingmethodstoreducethedensityofcomplexdisplays.
Table1-AlternativeCodingDimensionsforCRTApplicationsDimensionRecomnendedNumberofLevelsAlternativeAlicationsSymbologySize10-15maxIdentifydifferentcnmoonentsandtheiroperationalstatusHighlightdynamicvs.staticdataHighlightoperationalvs.non-operationalcomponentsDifferentiatepipingwithfl'owvs.noflowHighlightmoreimportantdata,symbols,orlinesDifferentiatemonitoredvs.non-monitoreddataLineStructureBrightness/IntensityColorAchromaticHighlighting3-43-4recom.on/offDifferentiateflowvs.noflowSuppressbackgroundinfoHighlightcautionandwarninginformationDifferentiateoperatationalvs.non-operationalcomponentsDifferentiatepipingwithflowvs.noflowDifferentiatedynamicvs.staticdataHighlightcautionandwa'minginformationHighlightcautionandwarninginformationDifferentiateoperationalvsnon-operationalcomponents CandidatesforCodinginProcessControlVariousmedia(steam,water...)Conditionsorstates(on/off,running/stopped,open/closed,flow/noflow.available/unavailable)Controlmodes(manual/automatic,remote/local)Plantstatus(pre-trip/post-trip,terminate/mitigate)Informationpriority(alarms)BackgroundorreferenceinformationversusforegroundinformationDataquality(good/inconsistent/bad/manuallyentered)~Informationstate(normal/cautioning/abnormal)
Therearemanyusefulideasonhowtoapplycodinqtechniquestodifferentapplications.Itisnotsufficienttomatchonecodingcandidatetoonecodingdimensionuntilthesetofcandidatesisexhausted.Thisapproachwillguarenteeanunsatisfactorycodingscheme.Codingquestionsmustbeexaminedasanintegratedsettogetherwithinformationtransferrequirementsgeneratedviataskanalysis.Thisapproachwillpreventconflictsbetweenindividualcodesanditwillpreventcodingschemeswhichincrease,notreduce,displaycomplexibi1ity.
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