characterizing and evaluating the arctic digital elevation model … · 2017. 6. 7. ·...

Arjan J.H. Meddens1*, Lee A. Vierling1, Jan U.H. Eitel1, Natalie T. Boelman2, Jyoti Jennewein1 & Andrew Maguire1

2a. Methods

Datasets:•ArcticDEM (5mresolutionproduct)

•AlaskanairborneLiDARdataset(black,Fig.2,Hubbardetal.2011)

Studyareas:Selectedsamplelocations(red,Fig.2)ofthe2011LiDARdataset:

§Location1:Arctictundravegetation,intermediatetopographicalcomplexity

§Location2:BlackandwhiteSpruceforest(open- closed),lowtopographicalcomplexity

CharacterizingandevaluatingtheArcticDigitalElevationModelproductwithLiDARdataforspatialmodeling

1. Introduction

• TheArcticDEM isapublic-privateinitiativetoproducedigitalsurfacemodelacrosstheArctic(Fig1).

• TheDEMisautomaticallycreatedbyusingopticalstereohigh-resolutionimageryat2mand5mspatialresolution(Noh&Howat,2015)

• CurrentlyArcticDEMsforAlaskaandpartsofCanada,Norway,Russia,andIcelandhavebeenproducedandareavailablefordownload

Objective:CharacterizetheaccuracyandnatureoftheArcticDEMdatasetforselectedregionsinAlaskawhereairborneLiDARisavailable

Acknowledgements: WewouldliketothankMikeWulder andJoanneWhiteforhelpfulcomments.ThisresearchwassupportedbyNASAABoVE projectsEitel-01andBoelman-01andtheUniversityofIdahoCollegeofNaturalResources.

References: Hubbard,T.D.,Koehler,R.D.,andCombellick,R.A.(2011).High-resolutionlidar dataforAlaskainfrastructurecorridors,inDGGSStaff,ElevationDatasetsofAlaska:AlaskaDivisionofGeological&GeophysicalSurveys,291p.Noh,M.J.,&Howat,I.M.(2015).Automatedstereo-photogrammetricDEMgenerationathighlatitudes:SurfaceExtractionwithTIN-basedSearch-spaceMinimization(SETSM)validationanddemonstrationoverglaciatedregions.GIScience &RemoteSensing,52,198-217

2b. Methods

AnalysisI: CompareelevationheightsoftheArcticDEM totheLiDAR-derivedbareearthandvegetationsurfacemodelsacrosstheselectedsamplelocations(using400randomlyselectedpixelsataminimumdistanceof100mfromeachothertoaccountforspatialautocorrelation)

AnalysisII: AssesseffectsofvegetationheightintheArcticDEM databycomparingatransectoftheArcticDEM,LiDARbareearth,andLiDARvegetationheightmetrics

Fig 2. Extent of the 2011 LiDAR data set (black) and the two selected sample locations (red).

Fig1. Illustration of the proposed ArcticDEMdomain. Note that only parts of the domain have currently been processed (source: pgc.umn.edu/arcticdem).

Fig. 3. Comparison between the ArcticDEM (x-axis) and LiDAR (y-axis) products (Location 1: top, Location 2: bottom; comparison with the LiDAR-derived bare earth: left and LiDAR-derived vegetation surface model: right). Data are 400 randomly selected pixels > 100 m apart.

3a. Preliminary results (Analysis I)• ThecomparisonsbetweentheArcticDEM andtheLiDARdatasetsshowverygoodagreement(R2s>0.99,RMSEs<7 m,andbiases<5m

• Thecomparisonsofthevegetationsurfacemodels(rightpanels)aremoreaccuratethanthebareearthmodelswithreducedRMSEsandbiases

• MorecomplextopographydoesnotreducetheoverallaccuracyoftherelationshipsbetweentheArcticDEMandtheLiDAR-derivedheightmetrics(notshown) 4. Conclusions

• TheArcticDEM isauniquedatasetusefulfortopographicandecologicalmodelingamongmanyotherapplicationsacrossthearctic-borealdomain(Fig.1)

• TheArcticDEM datashowgoodagreementtoanindependenthighresolutionLiDARdataset

• Usersshouldbeawarethatwhendense(forest)canopiesoccurinthedataset,theArcticDEM followsthetopofthecanopyratherthantheunderlyingtopographyofthelandscape

Nextsteps:• Includemorelocationswithmorecomplextopographyandvegetationstructure• DevelopavegetationstructureproductfromtheArcticDEM foranimalmovementandtreeline modeling

3b. Preliminary results (Analysis II)

• Intallanddensevegetation,theArcticDEM followsthetopofthecanopyratherthantheunderlyingtopographyandgapsof~10marenotcaptured(Fig4.)

Fig 4. Transect of 1400m from dense forest towards a more open vegetation valley bottom (see black line in the inset image). In black the ArcticDEM data is shown, in red the LiDAR-derived bare earth model, and in green the LiDAR vegetation height (with corresponding second y-axis), all units shown are in meters.

1University of Idaho, Department of Natural Resources and Society, Moscow, ID (*ameddens@uidaho.edu) 2Lamont Doherty Earth Observatory, Columbia University, Palisades, NY.

AK

Location 1

Location 2 Location 1

Location 2 Location 2

Location 1

BareearthcomparisonVegetationheightcomparison