基于DEM的地形特征提取及分辨率與地形因子的關系研究的中期報告Abstract:ResearchonterrainfeatureextractionandtherelationshipbetweenresolutionandterrainfactorsbasedonDEMThispapermainlystudiesthefeatureextractionoftopographybasedonDEMandexplorestherelationshipbetweenresolutionandterrainfactors.Firstly,thepaperintroducesthebasicprinciplesandcharacteristicsofDEM,andanalyzestheimpactofresolutiononDEMdataquality.Secondly,thecommonlyusedtopographicfeaturesareintroduced,andthefeatureextractionmethodbasedonthethresholdvalueisdiscussedindetail.Finally,therelationshipbetweenresolutionandterrainfactorssuchasslope,aspect,andelevationdifferenceisanalyzed,andtheresultsshowthatthehighertheresolutionofDEM,themoredetailedtheterrainfeatures,andthemoreaccuratethecalculationofterrainfactors.Keywords:DEM,topographicfeatures,thresholdvalue,resolution,terrainfactorsIntroduction:Digitalelevationmodel(DEM)isadigitalmodelthatexpressestheterrainheightoftheearth'ssurfacethroughgriddata.Itiswidelyusedintopographicanalysis,hydrologicalmodeling,environmentalassessment,resourceevaluation,andotherfields.ThequalityofDEMdatahasagreatimpactontheaccuracyofterrainanalysis.Amongthem,theresolutionofDEMhasasignificantimpactonterrainfeatureextractionandterrainfactoranalysis.ThispaperaimstoexploretherelationshipbetweenresolutionandterrainfactorsbasedonDEMandprovideareferencefortheselectionofDEMresolutioninterrainanalysis.1.BasicprinciplesofDEMDEMisadigitalmapthatreflectstheheightofterrainfeaturesontheearth'ssurface.Itiscomposedofamatrixofcells,andeachcellrepresentsasampleoftheterrainelevationatacertainlocation,whichisexpressedinunitsofmeters.DEMdatacanbeaccessedbyremotesensingdata,fieldsurveydata,orothersources,andthroughdifferentinterpolationmethods,suchastriangulation,splineinterpolation,andkriginginterpolation,toobtainthefinalterrainsurfacemodel.TheaccuracyandspatialresolutionofDEMarethekeystoaffecttheeffectivenessandaccuracyofterrainanalysis.2.TerrainfeatureextractionbasedonDEMTerrainfeatureextractionisanimportantapplicationofDEM,whichcanhelptoidentifyterraintypes,landforms,andgeologicalstructures.Thecommonlyusedterrainfeaturesincludeslope,aspect,curvature,elevationdifference,andterrainroughness.Amongthem,slopeandaspectarethemostbasicterrainfactors,whichcanbeobtainedbycalculatingthetangentoftheslopeangleandtheaspectangleoftheterrainsurfaceateachpoint.Thecurvatureoftheterrainsurfaceisthesecondderivativeoftheterrainheight,whichcanindicatetheconvexandconcavefeaturesoftheterrain.Theelevationdifferencereflectsthedifferenceinelevationbetweentwopoints,andtheterrainroughnessisthestandarddeviationoftheheightdifferencewithinacertainarea.ThethresholdvaluemethodisacommonlyusedmethodforterrainfeatureextractionbasedonDEM.Itsetsdifferentthresholdvaluesfordifferentterrainfeatures,suchasslope,aspect,andcurvature,toextractandclassifyterrainfeatures.Thespecificcalculationmethodisasfollows:Slope=arctan(Zx+Zy)Aspect=arctan(Zx/Zy)Curvature=d2z/dx2+d2z/dy2Elevationdifference=Zmax-ZminTerrainroughness=standarddeviationoftheheightdifference3.RelationshipbetweenresolutionandterrainfactorsTheresolutionofDEMdeterminesthedegreeofdetailoftheterrainfeatures,andaffectstheaccuracyofterrainfactorcalculation.Generally,thehighertheresolutionofDEM,themoredetailedtheterrainfeatures,andthemoreaccuratethecalculationofterrainfactors.Inthisstudy,weselectedfourresolutionsofDEM,including5m,10m,20m,and30m,toanalyzetherelationshipbetweenresolutionandthreeterrainfactors,includingslope,aspect,andelevationdifference.Theresultsshowedthatwiththeincreaseofresolution,theterrainfeaturesbecamemoredetailed,andthecalculatedterrainfactorsbecamemoreaccurate.WhentheresolutionofDEMwas5m,theslopeandaspectoftheterrainfeaturesweremoredetailed,andtheelevationdifferencewasmoreaccurate,whichcanaccuratelyreflectthedifferencesinterrainheightbetweendifferentareas.However,whentheresolutionofDEMwas30m,theterrainfeatureswererelativelyrough,andthecalculatedterrainfactorswerelessaccurate,whichcannotreflectthesubtledifferencesintheterrain.Conclusion:DEMisanimportanttoolforterrainfeatureextraction,andtheresolutionofDEMhasasignificantimpactonthequalityofDEMdataandtheaccuracyofterrainfactorcalculation.ThethresholdvaluemethodisaeffectivemethodforterrainfeatureextractionbasedonDEM.Inthisstudy,therelationshipbetweenresolutionandterrainfactorswasanalyzed,andtheresults