arcgis期末复习考点第八章

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1、Chapter8ReviewQuestions1.Explainthedifferencebetweenlocationerrorsandtopologicalerrors.Locationerrorssuchasmissingpolygonsordistortedlinesrelatetothegeometricinaccuraciesofspatialfeatures,whereastopologicalerrorssuchasdanglinglinesandunclosedpolygonsrelatetothelogicalinconsistenciesbetwee

2、nspatialfeatures.2.Whataretheprimarydatasourcesfordigitizing?Globalpositioningsystems(GPS)andremotesensingimageryprovidetheprimarydatasourcesfordigitizing.Thesedatasourcescanbypassprintedmapsandthepracticeofvariousmethodsofmapgeneralization.3.AdigitizedmapfromasecondarydatasourcesuchasaUS

3、GSquadranglemapissubjecttomorelocationerrorsthanaprimarydatasource.Why?AsecondarydatasourcesuchasaUSGSquadranglemapissubjecttomorelocationerrorsbecausethemaphasundergonesimplification,generalization,andotherpracticesduringthemapmakingprocess.4.AlthoughtheU.S.NationalMapAccuracyStandardado

4、ptedin1947isstillprintedonUSGSquadranglemaps,thestandardisnotreallyapplicabletoGISdata.Why?AGISusesdigitalspatialdata,whichcanbeeasilymanipulatedandoutputtoanyscale.TheU.S.NationalMapAccuracyStandard,ontheotherhand,isscaledependent.5.AccordingtothenewNationalStandardforSpatialDataAccuracy

5、,ageospatialdataproducerisencouragedtoreportaRMSstatisticassociatedwithadataset.Ingeneralterms,howdoesoneinterpretandusetheRMSstatistic?OnecanfirstmultiplytheRMSby1.7308togettheNSSDA(NationalStandardforSpatialDataAccuracy)statistic.Thisstatisticrepresentsthestandarderrorofthemeanatthe95pe

6、rcentconfidencelevel.Inotherwords,onecanbesurethat,95percentofthetime,theaccuracyofapointoralineiswithintheNSSDAstatistic.6.Supposeapointlocationisrecordedas(575729.0,5228382)indataset1and(575729.64,5228382.11)indataset2.Whichdatasethasahigherdataprecision?Inpracticalterms,whatdoesthediff

7、erenceindataprecisioninthiscasemean?Dataset2hasahigherdataprecisionthandataset1.Ifthemeasurementunitismeters,therecordingofapointlocationindataset2isdowntoonehundredthofameterandtherecordingindataset1isroundedoffatmeters.1.TheArcGISDesktopHelphasaposterillustratingt