ReliefPresentationonUSNationalParkServiceMaps
TomPatterson
USNationalParkService
HarpersFerryCenter
[email protected]
Chapterexcerptfrom:MountainCartography.16YearsICACommissiononMountain
Cartography.
http://carto.univie.ac.at/index.php?id=194016
Introduction
Thischapterexaminestheevolutionofreliefpresentationsonmapsdevelopedby
HarpersFerryCenter,themediaservicecenteroftheUSNationalParkService
(NPS).HarpersFerryCenterproducesstandardized“Unigrid”brochures,which
includethemapsusedbyparkvisitors.Whatfollowsisageneraloverviewoffive
parkmaps,eachwithadistinctivereliefstyleandmodeofproduction.Theyappear
inroughchronologicalorderoftheirdevelopment.Recentreliefpresentationsare
generallymoredetailed,colorful,andrealisticthanthosefromearlieryears.
Changingtechnologyislargelyresponsibleforthedifferentreliefstylesfoundon
parkmaps.Somerelieftreatmentstodaywerenotpossible,orimaginable,in1977
whentheNPSestablishedthebrochureprograminitsmodernphase.Landscape
heterogeneityisanotherfactorbehindthedevelopmentofdifferentreliefstyles.
Withover400parksitesrangingfromtheglacialmountainsofAlaskatotherolling
piedmontofVirginia,aone-style-fits-allapproachcannotadequatelydepictall
landscapes.NPSmapsservesome300millionparkvisitorseachyear.Ourongoing
efforttomakeunderstandablemapsforthisdiverseaudiencehasfurtherspurred
experimentsinreliefpresentation.
ThereliefpresentedonNPSmapsisgenerallynotasimportantasvisitor
information:pointsofinterest,facilities,roads,trails,etc.Toreflectthiscontext,the
reliefexamplesthatfollowareexcerptsfrompublishedparkmapscontainingall
classesofinformation.Theyarealsoexclusivelyplanimetric,sincedelvingintothe
intricaciesof3Dreliefpresentationiswellbeyondthescopeofonechapter.
Map1:ManualShadedRelief
Figure1.DinosaurNationalMonument,UtahandColorado,featuringanairbrushed
shadedreliefbyBillvonAllmen,1983.
Over35yearsagowhentheNPSUnigridprogramlaunched,oneofthemaingoals
wastobringparkmapsoutof“thedarkagesofline-workcartography”accordingto
VincentGleason,thenChiefofPublications(Hanna,1988).Hisvisionwasto
representterrainonmapswithuser-friendlyshadedreliefinsteadofhachuringor
contourlines.UnderGleason’sguidance,RRDonnelleyCartographicServices,the
firmhiredtodevelopparkmapswithanentirelynewlook,producedthefirst
shadedreliefmaps.Soonafterwards,theNPStappedcartographerBillvonAllmen
(1928-2013)tobethein-houseshadedreliefartist(Figure1).Hespentsixweeks
trainingattheSwissFederalOfficeofTopography(nowcalledswisstopo),andthen
wentontoproduceover80shadedreliefsbeforeretiringin1990.TomPatterson,
hiredin1992toreplacevonAllmen,hand-drew12reliefspriortoswitchingto
digitalproductioninthemid-1990s.Examplesfrombothartistsareavailableonthe
ShadedReliefArchivewebsite(seereferencesforURL).
VonAllmen’stoolofchoicewasthePaascheABairbrush,withwhichhesprayeda
mistofinkonmetalmount,atypeofpaperadheredtoanaluminumsheetfor
dimensionalstability.Heworkedfromcontourlinesappliedtothemetalmountasa
temporaryblueemulsion.Asalaststephewouldsprayammoniaonthecompleted
arttoremovethecontours,withoutdamagingtheairbrushwork.Bycomparison,
Pattersondrewreliefswitha4HpencilonDupontCronaflexUC-4draftingfilm.The
ricestarchsurfaceonthisfilmwasreceptivetosmudgingwithstumps,finely
pointedsticksmadefromrolledcardboardthatabsorbgraphite.Acontourbase
mapcouldbereadthroughthetranslucentdraftingfilm.Byslidingawhitesheetof
paperunderthedraftingfilm,Pattersoncouldseetheshadedreliefhewasdrawing
withoutthecontourlines.
Regardlessoftheproductionmethod,creatingmanualshadedreliefwasslowand
painstakingwork.Alargeparkreliefcouldtakeonemonthtocomplete.Manual
shadedreliefoftenappearshighlygeneralizedbecauseaddingdetailandrefinement
totheartrequiresevenmoretime.Giventhegreateffortthatwentintocreating
manualreliefart,thenaturaltendencywastofeatureitprominentlyonearlyNPS
maps,evenifitinterferedwithotherinformation.Printingoftheshadedrelief
becamelighteronsubsequentprintings.Onatypicalmapfromthateratherelief
wouldprintinblackandcombinewithflatareacolorsbuiltfromcyan,magenta,and
yellow.Halftonescreen-printingwouldcontrolshadowdensitiesontheshaded
relief,simulatingcontinuoustones.Thedensestshadowswere15percentblack,flat
areas4percent,andhighlights1percent.DinosaurNationalMonumentisoneofthe
fewremainingNPSmapsthatstillemploymanualshadedrelief(Figure1),although
adigitalversionwillreplaceitin2015.
Shadedreliefscreatedmanuallyreflectindividualartisticstyles,andtheyvaryin
appearance(Figure2).Ifanartisthadtoredrawareliefofthesamearea,thesecond
versionwouldlookslightlydifferentfromthefirst.Ontheotherhand,NPSshaded
reliefartexhibitscommontraits,regardlessofwhodrewit.Modulatedlightand
shadowscreatetheimpressionof3Dterrainonaflatsheetofpaper.The
illuminationsourceisfromthenorthwest(upperleft),andprominentfeatures
receivemostemphasis.
Figure2.Manualreliefexamples:(Left)HotSpringsNationalPark,Arkansas,byRR
Donnelley.(Center)GrandTetonNationalPark,Wyoming,byBillvonAllmen.(Right)
CityofRocksNationalReserve,Idaho,byTomPatterson.
Map2:DigitalShadedRelief
Figure3.DigitalshadedreliefofOlympicNationalPark,Washington.
Theswitchfrommanualtodigitalcartographystartinginthe1990srevolutionized
NPSshadedreliefproduction.Whathadbeenthemostdifficultmapelementto
produceeventuallywouldbecomeoneoftheeasiest,reducingproductiontimefora
basicrelieffromafewweekstoafewminutes.
Theswitchtodigitaldidnothappenovernight.Inadequatesoftware,lackofan
integrateddigitalworkflow,andpoororunavailableelevationdatahamperedearly
productionefforts.Forexample,USGSdigitalelevationmodels(DEMs)fromthat
timesufferedfromterracingandstripingartifacts,whichyieldeduglyblemishes
whenrenderedasashadedrelief.Inaddition,thevalleybottomswereoftenoutof
registrationwithdrainagelines.Usingtheseflaweddatatoproduceabarely
acceptableshadedreliefrequiredhoursofeditinginAdobePhotoshop.Itwasoften
moreconvenienttoscananoldmanualshadedreliefforanewparkmapotherwise
madefromdigitaldata.Nowadaysthesituationismuchimproved.TheNPSuses
NaturalSceneDesignerProsoftwaretoefficientlyproduceshadedreliefsfrom
artifact-freeDEMsacquiredfromtheUSGSNationalElevationDataset.
TheNPSinitiallypresenteddigitalreliefonmapsinthesamemannerasmanual
relief,lightlyprintingitasbackgroundblack(Figure3).Incontrasttomanual
shadedrelief,afrequentproblemwithdigitalreliefisexcessivedetail(Figure4).
TheDEMsfromwhichthereliefderivesoftencontainmoredetailthanthat
necessaryonavisitormap,inadvertentlyproducingvisualnoise.TheNPSalleviates
thisproblembydownsamplingDEMspriortorenderingshadedreliefs,then
applyingthemedianfiltertotherenderedartafterwardsinPhotoshop.Themedian
filtereliminatessmallterraindetailswhilepreservingthelargerfeatures.Terrain
SculptorsoftwareisanothermethodusedbytheNPStogeneralizeDEMsbefore
reliefrenderingtakesplace(Leonowiczet.al.,2010).TheNPScompletesashaded
reliefbyaddingcontrastathigherelevationstoincreasetheapparentthreedimensionalityofmountains.UsingagrayscaleDEMasaPhotoshoplayermaskand
applyingextratonetomountaintopshadowsaccomplishesthisenhancement.The
aerialperspectiveeffectdevelopedforSwisstopographicmapsisthebasisforthis
technique(Imhof,1982).
Arecenttrendistoprintdigitalreliefincolorsotherthanblack.Forinstance,using
lightbeigereliefforasouthwesterndesertparkevokesanaridenvironment.Beige
reliefalsointerfereslesswithblacktypeandsymbols,improvingoverallmap
legibility.Printingshadedreliefsincolorsthatmimicthenaturalenvironment
introducesthenexttopicofthischapter,naturalcolors.
Figure4.OlympicNationalPark,Washington.(Left)Manualshadedreliefcreatedby
BillvonAllmen.(Right)Digitalshadedreliefrenderedfroma90-meterDEM.
Map3:NaturalColor
Figure5.KenaiFjordsNationalPark,Alaska,innaturalcolor.
ThepopularizationofnaturalcolormapsstartedwithUSGScartographerHal
Shelton(1916-2004).Workingonhisowntime,Sheltondevelopedaseriesofroute
mapsforairlinepassengersduringthe1950sand60s,whenairtravelwasfirst
becomingcommonplace(PattersonandKelso,2004).Hebelievedthatforhismaps
tobeeffectivetheyshouldusecolorsresemblingthosethatpassengerscouldseeon
thegroundbelow.Withtheassistanceofateamofacademicgeographerswho
compiledlandcoverinformationonbasemaps(Earthmonitoringsatellitesdidnot
existthen),Sheltonpaintedbeautifulandrealisticmapsusinganaturalpalette.Ifan
areawasconiferousforest,hepainteditdarkblue-green;ifitwasdeciduous,
mediumgreen;grassland,lightyellow-green;andsoon.
Shelton’sapproachtomappingwithcolorsfoundinnatureseemedapplicableto
largeexpanseslikeKenaiFjordsNationalPark,Alaska(Figure5).Unlikethe
traditionalmapofDinosaurNationalMonument(Figure1),whichemploysan
arbitrarycolorchoice,flatgreen,thevaryingcolorsontheKenaiFjordsmaphelp
usersbetterunderstandlandcoverandtherelatednaturalenvironment.
Creatinganaturalcolorparkmapisaccomplishedwithrasterlandcoverdata,such
asNationalLandCoverDataset(NLCD),availablefortheentireUSat30-meter
resolution.Likepaintingbythenumbers,butusingpixelsinstead,thegarishcolors
oftheoriginallandcoverimageareswappedforanewpalettederivedfromnature
(Figure6).Landscapephotographsavailableonpopularonlinesitesareagood
sourceforappropriatenaturalcolors—colorselectionisasimplematterof
samplingthemwiththe“eyedropper”toolinPhotoshop.Subtlecolorsworkbest.In
addition,atlargermapscales,assigningorganictexturestothelandcovercolors
producesamorerealisticappearance.Forexample,theKenaiFjordsmaphassubtle
texturesrepresentingtreecanopyandglaciersurfaces.Asafinishingtouch,
standardshadedreliefilluminatedfromthenorthwestdefinesthetopographic
forms.
Naturalcolormapsareasynthesisofsatelliteimagesandshadedreliefmaps.
Althoughnaturalcolormapsoftenlookrealistic,theydifferfromaerialimageryby
whattheylack—haze,castshadows,clouds,andunneededphotographicdetail
(Patterson,2002).Theyareessentiallyreconstitutedsatelliteimagesoptimizedfor
cartographicdepiction.Naturalcolormapsarenotwithoutproblems,however.The
naturalworldcanbedisorganizedanduntidy,andsotooaresomenaturalcolor
maps.Iftoohighlytexturedandboldlyprinted,overallmaplegibilitycansuffer.And
naturalcolormapsdonotcombinewellwitharbitraryareacolorsrepresentingland
ownership.Itisbesttodepictpropertyparcelswithsimpleboundinglinestoavoid
colorconfusion.
Figure6.KenaiFjordsNationalPark,Alaska.(Left)NationalLandCoverDataset.
(Right)Naturalcolors,textures,andshadedreliefappliedtoNationalLandCover
Dataset.
Map4:TextureShading
Figure7.GlacierNationalPark,Montana,withrocktexturesappliedtosteepslopes.
TextureshadinghasbecomeacommonelementofNPSreliefpresentationssince
the2010introductionofthetechnique(Brown,2014).TextureShadingisproduced
byTerrainTextureShader,softwarethatdetects,amplifies,andrendersslight
variationsinDEMsasimageswithincreasedcontrast(Figure8).Byitself,texture
shadingistoodarkandcontrastingtohavecartographicutility.Butwhenmerged
withshadedrelief—therecommendedproportionsare60percentshadedreliefand
40percenttextureshading—itenhancestheshadedrelief.Theadditionoftexture
shadingrevealssubtledetailsonilluminatedslopesandinflatareasnotevidenton
theoriginalshadedrelief(Figure9,center).Themergedresultshaveaflattertonal
rangethatworkswellasabackgroundonmapsfilledwithothertourist
information,especiallywhenthereliefislightenedandcolorized(Figure9,right).
Textureshadingismostbeneficialinlow,irregulartopography,likeglacialdeposits
anderodedbadlands.
Figure8.GlacierNationalPark,Montana.(Left)AgrayscaleDEM.(Right)Atexture
shadingcreatedfromtheDEMatdefaultsettings.
Figure9.GlacierNationalPark,Montana.(Left)Shadedrelief.(Center)Mergedshaded
reliefandtextureshading.(Right)Themergedresultslightenedandcolorized.
Mountainlandscapesalsocanbenefitfromthetextureshadingtechnique,whichcan
yieldacceptablerocktexturesfromDEMsunderidealsituations(Patterson,2014).
Mountainswithhorizontalrocklayers,suchasthoseatGlacierNationalPark,
Montana,arebestsuitedtothetechnique(Figure7).Toproducerocktextures,one
firstmustrenderatextureshadingwithmaximumdetailandcontrast.Thisvisually
noisyimageisthencombinedwithashadedreliefmadefromthesameDEMin
Photoshop,andwithaslopelayermasktoapplyitonlytothesteepestslopes.Other
enhancementstoGlacierNationalParkmapincludegreenlowlandhypsographyin
thedeepestvalleys,yellowsunlightonilluminatedslopes,andcomplementarycool
blueonshadowedslopes.Swisstopographicmapsinspiredthecolorscheme.
Map5:HybridGeospatialImages
Figure10.PetrifiedForestNationalPark,Arizona,featuringaLandsat8satellite
imagecombinedwithshadedrelief.
AgrowingtrendonNPSmapsistheintegrationofgeospatialimages—satellite
imagesandaerialphotographs—withreliefpresentations.Theuseoftheseimages
wasatfirstsparing.Forexample,naturalcolormapswereenhancedbyselectively
borrowingglacierandforesttexturesfromaerialphotographs.Morerecently,the
NPShasbegunusingimagesasthedominantcomponentinreliefpresentations
(Figure10).Theincreasednumberofsourcesforfreeimagedatahasencouraged
thisexperimentation.NationalAgriculturalImageryProgram(NAIP)andLandsat8
aretheimagesusedmostoftenonNPSmaps.
Usinggeospatialimagesinreliefpresentationsworksbestonlandscapeswithlow
relief,suchaslavaflows,braidedrivers,marshes,shallowwaterbodies,anddeserts.
Forexample,themapofPetrifiedForestNationalPark,Arizona(Figure10)uses
Landsat8,whichcapturestherichcolorsofthePaintedDesertandanetworkofdry
streambeds.Itgivesatruerpictureofthatdesertenvironmentbeyondwhatis
possiblewithtraditionalcartography.Depictingthemanydrystreamswith
conventionalbluelines,forexample,wouldimplymorewaterthanwhatnormally
exists.
Landscapeswithlowreliefhaveanotheradvantageongeospatialimages:fewer
shadows.Shadowscastbythesunonlandscapesurfacesandembeddedinimages
areamajorproblemwhenmakingreliefpresentations.Thehighertheterrain,the
denserandmoreobscuringtheshadowsbecome.Acompoundingproblemisthe
lightdirectionongeospatialimages,typicallyfromthesoutheast(lowerright),
whichplacesshadowsonnorthwest(upperleft)facingslopeswhenimagesare
north-oriented.Theresultis“terraininversion”:Mountainsappearasvalleys,and
viceversa.
Removingembeddedshadowsfromimagesisnotfeasibleinmountainousterrain
withthedensestshadows—moredamagethangoodresultsfromimageediting
procedures.However,onimageswithlowrelieforlimitedareasofhighrelief,
shadowremovalisaworkableoption.Thebestimagestousearethosetaken
aroundthesummersolsticewhenthesunishighestandshadowsareshortest.After
removingtheshadowsfromthegeospatialimage,onecanthenmergetheimage
withconventionalshadedrelieftocreateahybridproductwithpositivetraitsof
both;shadedreliefthatreadsproperly,plusrealisticandattractiveimagetextures
(Figure11,right).
TheNPSremoves,oratleastneutralizes,embeddedshadowsfromimagesusingtwo
AdobePhotoshopprocedures.Thefirstprocedureworksbestonimageswithlight
ormoderateshadowdensities.Itinvolveslighteningtheshadowswitha
Brightness/Contrastadjustment.Toselecttheshadowstoapplythisadjustment,
onemustfirstcreateashadedreliefmaskfromaDEMofthesameareathatmatches
thesunangleandazimuthoftheimage.ThemetadatafileaccompanyingLandsat8
imagesprovidesthisinformation.
Thesecondprocedureappliestoimageswithboldshadowsthatcompletelyobscure
landsurfacetextures.TheNPSselectstheseshadowswithPhotoshop’sMagicWand
toolandusesContentAwareFilltoautomaticallyreplacethemwithtextures
borrowedfromelsewhereontheimage.Thisprocessispotentiallyinaccurateand
misleading.Aftermergingashadedreliefwiththedoctoredimage,however,the
brightlyilluminatedslopesonthereliefcompletelycoverimageareasthatwere
formerlyshadows(Figure11).Printingthegeospatialimagelightlywhenmerged
withshadedreliefalsoamelioratesthisproblem.Theobjectiveistoshowahintof
imagedetailonallbutthesteepestslopes.
Figure11.PetrifiedForestNationalMonument,Arizona.(Left)ALandsat8imagewith
embeddedcastshadows.(Center)ShadedreliefcreatedfromaDEMofthesamearea.
(Right)MergedLandsat8andshadedrelief.
Conclusion
Therelieffoundontoday’sNPSmapsreflectsanevolvingarrayofstylesand
techniques.Decidingwhichstyleofrelieftousedependsonmanyfactors,including
availabledata,terrainandlandcovercharacteristics,mappurpose,andtime
constraints.Forexample,creatinganelaboratenatural-colorreliefofGreatSmoky
MountainsNationalParkinthesouthernAppalachianswouldservenouseful
purposebecauselittlelandcovervariationexists—theparkismostlywoodedfrom
valleybottomtoridgetop.Abasicshadedreliefperhapscombinedwithtexture
shadingcasewouldsufficeinthiscase.
Recentlydevelopedstylesofreliefpresentationhavenotnecessarilysupplanted
earlierstyles.Whilethe1970sand80sweretheheydayofmanualreliefshading,
theNPSstillappliesmanualtouchupstodigitalreliefs—usingPhotoshopanda
Wacomtablet—tomeetdesignneedsnotpossiblethroughautomatedmeans.For
example,theKenaiFjordsmap(Figure5)hasahand-drawnoceanbottombecause
digitalbathymetricdatawasnotyetavailableforthatareaatthetimeofmap
production.Andsomenewermapscombinereliefpresentationstyles.Canyonlands
NationalPark,Utah,forexample,employsthreeofthestylesdescribedinthis
chapter(Figure12).
Onthewhole,reliefpresentationonNPSvisitormapshaschangeddramatically
sincetheUnigridbrochureprogrambeganin1977,andcontinuestoevolve.As
softwareanddataimprove,sotoowillthereliefpresentationsonparkmaps.
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