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VisualizationandAnalysisoftheSwissAvalanche

BulletinusingGPS

HeiriLeuthold

andBrittaAllgöwer

KeyWords:Avalanchebulletin,GIS,hazardmapping,diction as well as judgement of the actual local risk must
visualizationbe left to the user. However, a tool for testing the forecast's
accuracy wasanticipatedwhichenables theAvalanche
ABSTRACT^{Warning Service to judgethe forecast results.}
Forthe visualizationof the (verbal) Swiss avalanchebulle-^{LAWIPROG doesnot calculate a new bulletin oreven}
tin a GISprototype wasdevelopedwhichaimsat thepredic-^{thehazardlevelfromtheoriginalmeasuringdata.The}
tion of the local avalanchehazardin a scaleof 1:25'000. For^{avalanche bulletinisstillproduced traditionallybythe}
this purposeweightfactors arederivedfrom the actualbul-^{experts. Only then LAWIPROG translates the derived haz-}
letin concerningthebulletinhazardlevel, thecriticalvalues^{ardconditions intoa spatialandcartographiclanguagethus}
for altitude,slope andaspect.Maininputdatais ahighreso-^{pointing out the "green orred spots" (see Fig. 5 and 6),as}
lutiondigitalterrainmodel(25x25meters).AsGIS-^{indicated in the text of the bulletin.}
SoftwareARC/INFO7.04wasusedand inparticularits^{For themodelingof the localhazardmaps specialweight}
raster data module GRID. The prototype is based on AML-^{factorswereassignedtothevariousinputparameters}
scriptsand iscompletelymenu driven.Whenever anew^{(slope,aspect,etc.).Thebasicideabehindthisis,that}
bulletinappearstheGIS-basedcalculations canbeper-^{LAWIPROG"simulatesaskilledskitourist"whojudges}
formed withina fewminutesandbe usedto adjust theaccu-^{snow and avalancheconditionsby consulting the bulletin,}
racy of the bulletin before its release. The evaluationof the^{readingmaps, taking into accountweather conditions, etc.}
prototype willtake placeduringwinter 1996/97; it includes
the comparison of the predictedavalanchehazard and ob-^{USE OF AGEOGRAPHICAL INFORMATIONSYSTEM (GIS)}
served avalanchesas well as statistical tests.Avalanchesrepresentspatial processes and illustrate very
clearly whatimpact topographicalstructures may have.GIS
INTRODUCTION^{are designedto analyse andmodel spatial data; they are an}
Swiss avalanche forecast has been performed forover50^{efficient tool formodeling dynamic processes such as the}
years by the SwissFederalInstitutefor Snow andAvalanche^{spreadofanavalancheandtoputtheresultsintoa}
ResearchWeissfluhjochDavos(SFISAR).Thebulletin^{geographical aswell ascartographical context.Bycom-}
covers the whole SwissAlps or approximately 25'000 km ² .^{biningexistingdataandmodelsnewinformationsand}
It refers tothe European avalanche hazard scale (Pahaut^{models can be gained. Heterogenous data (scale, thematic}
1994,SFISAR 1994),differs among five hazard levels and^{layers, measuring regime, etc.) may be overlayed andinte-}
indicates the actualhazardousconditions thus helping the^{grated to a common data set.One of the great advantages}
user where to look forthe areas of potential danger. So far^{and alsoGIS-researchtopics areinterpolationand extrapo-}
thebulletinisaplaintextandoffersonlyverygeneral^{lationproceduresforareasbetweenmeasuringpoints.}
visualization facilities for thespatial dimension to theuser.^{MoreoverGIS produce cartographic products which need}
Inordertoaccurately interpretthebulletinspecialised^{notgothrough timeconsuming(analogue) mapproduc-}
knowledgeand goodmap readingcapabilitiesare required.^{tion processes.The result of an analysis can be shown on}
Professionalshowever,manageperfectlywellbutski-^{the computer screenor printed immediately. Such"instant}
touring and off-piste skiing become more and more popu-^{maps"(Allgöwer1995)mayhavethecharacterof}
lar.Thereforeanincreasing numberofpeoplewith less^{hypothesis and can be recalculated again and again until}
knowledgeand skillsattempttotravelthebackcountry.^{they fit their purpose.}
Reliable and easy to understand forecasting systems - not^{LAWIPROGwas programmed using ESRI's 1ARC/INFO}
onlyforavalanches -are hence ofgrowinginterest and^{as GIS-Software.All spatial modelingis donewiththeraster}
importance.^{module GRID and all programs are written in Arc Macro}
Language(AML). LAWIPROG is an interactive application
TOPICS^{andhas auserinterface which requires nospecialGIS-}
This growingdemandfor "visual andeasy to interpret data"^{knowledge from the end-user.}
encouragedtheauthorstodeveloptheGIS-prototype
LAWIPROG forthevisualizationofthe Swissavalanche^{THE SWISS AVALANCHE BULLETIN}
bulletin.Special emphasis was put on the transformation^{The Swiss avalanche bulletin is designed as a forecasttool}
oftheglobaltothelocalhazardpredictionandits^{and publishedabout one hundredtimes duringwintertime}
cartographicrepresentation in a scale of 1:25'000.^{by the Avalanche Warning Service, a small group of five}
The authors are well aware of the fact that the original^{experts at SFISAR. The input data are assembled through}
bulletin is designed forlarge-scale statements where pre-^{fourmain country-wide networks,gathered in the Snow}
and Avalanche Information System (Meister1994):

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