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6/29/2015 ExaminingGPSData(GPSandGIS)Part2

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ExaminingGPSData(GPSandGIS)Part2

PROJECT3AVolcano

WebeginbylookingatafilegeneratedbyaGPSreceiverthatcircumnavigatedKilaueaCaldera,theactivevolcanoontheislandofHawaii.Beforeyoucanseeoranalyzethedata,however,severalparametersmustbesetup.(Right.JustaswhenyouusedtheGPSreceiver.Itturnsoutthat,whenyoudoGPSforGIS,aconsiderablepartoftheactivityisgettingsettingsright.Sorry.)

Closeallopenwindows(exceptthemainone,ofcourse).Maximizethewindow.

{_}IntheFilemenu,pickProjects.Clickonthefieldnextto"ProjectName."Find"Default"inthedropdownlist(youmayhavetoscrollthelistupordowntoseealltheentries)andclickonit.Okayyourchoice.

{_}Underthe"Options"menu,select"CoordinateSystem."Youwantto"SelectBy""CoordinateSystemandZone"(ratherthan"Site").The"System"shouldbe"Latitude/Longitude"andthe"Datum""WGS1984."Altitudeshouldbemeasuredfrommeansealevelinmeters(usetheEGM96[Global]Geoid)."OK"yourchoices.

{_}Under"Options~Units"pickkilometersfortheDistancemeasurement.

{__}Under"Options~TimeZone"pick"Hawaii."NoticethatHawaiiantimeis10hoursearlierthanGreenwich(UTC)time.

{__}Alsounder"Options,"turnoffallfive"bars"(four"Toolbars"andthe"StatusBar")byclickingeachsothatthecheckbesidethetoolbarnamedisappears.NowturnontheStandardtoolbar.Runthemousepointeroverit,pausingovereachbuttonlongenoughtoreadtheexplanatoryboxthatappears.DothesamenowfortheMousetoolbar.AddandcheckouttheProjecttoolbar.LikewisetheUtilitytoolbar.Finally,maketheStatusBarappearatthebottomofthewindow.(Partofthetricktooperatingcomplexsoftwareisreadingandunderstandingvariousmessagesthatitprovidesthatis,keepingupwiththestatusoftheprogram.Anotherpartisknowingthemajorcapabilitiesillustratedherebyvariousbuttonsonthetoolbars.)ThecompletedwindowwilllooklikeFigure210inthelasttopic.

{_}UnderOptions,instructthesoftwarenottosavethewindowlayoutwhentheprogramisexited.

{__}FromtheFilemenu,clickon"Open."Awindowentitled"Open"willappear.(Toachievethesameeffect,youcouldalsohaveclickedonthelittleyellowfilefoldericonattheleftofthestandardtoolbar.)

{__}Fillintheblanksinthewindowsothatthedirectoryis__:\GPS2GIS\HAWAII5andthefileis"Volcano.ssf."(Thefollowingstepcontainsdetailedinstructions.)

{_}Navigatetothecorrectfile:

(1)clickonthelittledownarrowinthe"Lookin:"boxand,fromthedropdownlistwithamouseclick,pickthechoicethatsayssomethinglike"MyComputer"or"ThisComputer."(Usethesliderbarorarrowsattherightofthewindowtoseeallthechoicesifnecessary.)

(2)withinthelargewhiteareaofthe"Open"windowselecttheiconassociatedwiththediskdrive"__:"withasinglemouseclick(itwillbecome

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highlighted)andtapthe"Enter"key(ordoubleclickontheicon,whichcomestothesamething)

(3)pounce6on"Gps2gis"fromthelistthatappears(youmayhavetousethesliderbarattherighttogettoit)alternativelyusethedownanduparrowkeystomovethehighlight)

(4)pounceon"Hawaii"(ifyoupounceonthewrongitemyoucanbacktrackbyclickingthefilefolderwiththe"uparrow"nexttothe"Lookin:"box)

GPStrackaroundKilaueaCalderavolcano.

Figure32.GPStrackaroundKilaueaCalderavolcano.

(5)the"FilesofType"boxshouldsay"Datafiles(ssf,cor,phs,imp)."(Ifitdoesnt,selectthisoptionfromthedropdownlist.)

(6)under"FileName:"select(withasingleclick)"Volcano.ssf"butdontopenthefileyet.Note,fromtheinformationatthebottomofthe"Open"window,thatthedatacollectionstarttimewasapproximately2:50P.M.,localtime,on15February1994.Thefileismadeupof110pointsandoccupies12.9kilobytes(KB)ofstorage.(Ifitdoesntsaythis,youdidsomethingwrongabove.Forexample,ifyoupickedtheincorrecttimezone,thedateand/ortimemightshowupincorrectly.)Nowclickthe"Details"button(itstothefarrightofthe"Lookin:"box)toseeinformationaboutthisandtheotherfilesinthisdirectory.Youcanseefilename,size,type,datethefilewaslastmodified,andattributeseitherbymovingthehorizontalsliderbarorresizingthecolumnwidthsbydraggingtheirseparatorbars.

{__}Click"Open."

{__}Displaythemapbyclicking"Map"inthe"View"menu.ItmaylooksomethinglikeFigure32.Oritmaynot.Oritmaybethatnothingappearsinthewindowatall.Nomatter!Youhavealotofcontrolovertheappearanceofthemap,asyouwillseeinthenextfewsteps.

{_}Fromchoicesthatshowupunder"View,"select"Layers"then"Features."Thewindowthatshowsup(FeatureLayers)containsalistoffeaturetypenames.

Thedatayouareworkingwithconsistsofsimplepositiondata(fixesconsistingofalatitude,alongitude,analtitude).InPathfinderOfficesuchrawdataarecalled"NotInFeature"data.(Positionsmayalsobecollectedinsuchawayastobeassociatedwithparticularfeatures,suchasroadsortypesofvegetation,andthesefeaturesmayhavenamesIlldiscussthecollectionofsuch"featureattributedata"laterindetail.)



Figure33.Definingfeaturetypesymbology.

{_}Tochangethewayrawpositiondataappearonthescreenmap,singleclickon"NotInFeature"soitishighlighted.Aboxnexttothenameshowsthesymbologywithwhichdataaredisplayed.Acheckmark,toggledwithamouseclickintheboxinthe"Show"column,determineswhetherthelayerwillbevisibleornot.Makecertainthat"NotInFeature"hasacheckmarkbesideit.Thedatayouareworkingwithconsistsofindividualpointsthatarenotpartofanyotherfeaturehencethe"NotInFeature"designation.(Makesurethe"View"optioninthiswindowissetto"Asabove.")

{_}Inthissamewindow,press"LineStyle."A"NotInFeature"windowappears.Hereyoucanselectasymbolcolor,alinethickness,andwhetherornotyouwantadjacentdatapointsconnectedwithlinesegments.Pickamediumlineofredcolorwiththedatapointsnotjoined.(PleaseseeFigure33.)Okayyourchoice.

{_}Verifythatyourchoicesof"LineStyle"madeittothe

"FeaturesLayers"window.ClickOKthere.NowthemapshouldlooklikeFigure32(exceptforthecolor).(Dont"Maximize"thiswindowifyoudothemapscaleanddistanceinformationbaratthetopofthewindowwilldisappear!)

ExploretheMap

{_}Whatmapscaleappearsonthemap?_.

Amapscalecanthereforebeconsideredasinglenumber,namelyafractionitisusuallymuchlessthanone(1.000)itsformis1dividedbyx,where"x"isusuallyanumbermuchlargerthanone.Amapscaleisaratio:thedistanceonagivenmaptotheequivalentdistanceontheearthssurfaceeachnumberexpressedinthesameunits.Ifthenumber"x"isone(1.0000)themapissaidtohavefullscale.Otherwaysofputtingitwouldbethatthemapscaleis1.0/1.0,or1:1,or1to1allofwhichimplyfullscale.Farmerswouldobjectifyoubeganunrollingsuchmaps.Asthescalegetssmaller(nearerzero)lessdetailisdisplayedandmorerealestateisshownonagivensizepage.Manypeopleincorrectlyreversethemeaningoflargeandsmallscaletheylookatthedenominatorofthefraction,ratherthanthefractionitself.A1:250scalemapisalargerscalemapthana1:500scalemap.Onedividedby250is0.004oneover500is0.002.Thenumber0.004islargerthanthenumber0.002.Rememberitthisway:Largerscalemapshavealargerdegreeofdetail.



{__}Doesthenumberofkilometersindicatedatthetopofthemaprefertothedistancefromonesideofthetracktotheother,ortothewidthofthewindow?_(Hint:resizetheeastwestdimensionofthewindow.)

{_}Experimentwithdifferenttypesof"Distance"unitsfromthe"Units"window,createdbyselectingfrom"Options~Units."Notethechangeinthevalueoftheeastwestdimensionofthewindow(showninthemapborderatthetop)reflectingthatdifferentunitshavebeenspecified.Tryinches.7Finishupbyselecting"Meters"asthedistanceunitsforthedatasetdisplay.

{__}Sinceyouhaveresizedthewindow,youmaywanttheimagetofillit.SelectView~Zoom~Extentsandnotetheresults.Nowresizethewindowagainsothatpartofthefigureiscutoff.Thistimefindthemagnifyingglassiconwiththeequalsign(=)initpressit.Againyougeta"ZoomtoExtents."8

{__}Inthe"Units"window,setthe"Area"tobe"Hectares."(Ahectareis1/100ofasquarekilometer.Ahectarecontainsthesameareaasasquarethatis100metersonasidebutofcourseitmighthaveanyshapethereareabouttwoandahalfacresinonehectare.)Setthe"NorthReference"tobe"Magnetic"(AutomaticDeclination),soPathfinderOfficewillautomaticallycalculatethedeclination(i.e.,thedifferenceindegreesbetweentruenorthandmagneticnorth).9

Themapwillshowfeaturesorientedtowardtruenorthregardlessofwhether"True"or"Magnetic"Northisselected.HoweverwhentheMeasurecapabilityofPathfinderOfficeisused,thedirectionofmeasuringlineswillbeshowninTrueorMagneticdegrees,dependingonwhichisselected.

{_}Under"Options~StyleofDisplay"choosethe"Lat/Long

Format"DD*MMSS.ss"whichwillcausethesoftwaretodisplaylatitudeandlongitudecoordinatesintheformofdegreesfollowedbyminutes,followedbysecondsincludingdecimalfractionsofseconds.10TheotherformsofdisplayareDD*MM.mmmandDD.ddd.Couldyouexpress493030.66"(fortyninedegrees,thirtyminutes,andthirtypointsixsixseconds)intheseothertwoforms?

Thereare60minutesinadegreethereare60secondsinaminute.

{_}Nowunder"Options~StyleofDisplay"changethe"Lat/Long

Format"toDD*MM.mmm.Pushthe"Select"button(itsiconisanarrow,pointingaboutnorthnorthwest).Movethepointeraroundthemapandobservethechangeinthe"minutes"valueshownontheStatusbar.Recallthataminuteoflatitudeisabout1845meters.Ingeneral,theStatusbarwilldisplaythecoordinatesofthemappositionindicatedbythepointer.

{__}Changethestyleofdisplayto"DD.ddd."

{_}Determinesomedatapointcoordinates:Slidethepointerdownoverthemap.Notethestatusbar(atthebottomofthescreen):thenumberstheretellthelatitudeandlongitudeoftheendofthepointerindecimaldegrees.Positionthepointernearthecenterofthe"oval"madebytheGPStrack.Writedownalatitudeandlongitude:__________.IfyouclicknearapointontheGPStrack,an"X"willappear,jumpingtothenearestdatafix.Trythis.Ifyoumovethepointeroffthemapwindowthestatusbarwilltellyouthecoordinatesysteminuse.Trythis.

AnumberofInternetsitesallowyoutodisplaymapsatvariousscales.Atthetimeofthiswriting(andbearinmindthatworldwidewebsitesareconstantlyinflux)therearesitesthatallowyoutoputinlatitudelongitudecoordinatesandobtainamapofthesurroundingterritory.Somesuchsitesarewww.mapquest.com,www.esri.com,www.mapblast.com,andwww.mapsonus.com.

{_}IfyouhaveaccesstotheInternet,minimizePathfinder

Officeandgotoasitesuchaswww.mapquest.comandfindwhereyoucangetamapbasedonitslatitudeandlongitude.Typeinthelatitudeandlongitudevaluesyouwrotedownabove(rememberingthatwestlongitudesarenegativenumbers).Ifthemapservingpeoplehavedonetheirjobcorrectlyyoushouldseeamapoftheroadaroundthevolcano.ThecentrallocationindicatedonthemapshouldbeapproximatelythelocationyouindicatedonthePathfinderOfficeportrayaloftheGPStrack.NotethesimilaritywiththeGPStrack.

{_}BackinPathfinderOfficewiththeMapwindowactive,usingthemouse,runthepointeralongtheiconsonthemousebar.Usuallyanexplanatoryboxappearsifyoupausebrieflyoveranicon.Findtheonethatallowsyoutomeasuredistancesonthemap.(Itlookslikearuleryoucanalsofinditsequivalent"Measure"inthe"Data"menu.)

{_}Measuresomedistances:Click"Measure."Ifyounowclickanylocationonthemapnearaverticaledgeandthendragthecursoraround,youcanseethattheStatusBardisplaysthedistanceanddirectionofthelineintheunitsyouhavesetforthedisplay.Measurementtakesplacetothelittle"+"signcursor.Swingthemeasuringlinearoundsothatitisvertical,towardthenorth.Notethatmagneticnorthisabout10totheeastoftruenorth.Thatis,togodirectlynorthyouwouldhavetofollowacompasscourseof350.

{_}Ifyounowclicktheleftmousebuttonagainyouwillanchorthemovingendofthelineandwillseeadisplayofthelengthanddirectionoftheline.Youcancontinuethemeasuringprocess,althoughyounolongergetimmediatedisplaysofthevalues.Eachtimeyouclickthemousebuttonyougetanotheranchorandindicationofthetotaldistancemeasuredfromthefirstanchortothelast.Thedirectionofthelastlineanchoredisshownas"Bearing."Youalsogetareadingfor"Area."

Undertherightconditions,ifanimaginarylineweredrawnfromthelastanchortothefirstanchor(thestartingpoint),thesequenceoflinesmightdefineapolygontheareaindicatedistheareaofthatpolygon.Ifthepolygonisnotproperlydefined(thatis,ifanyoftheselines[includingtheimaginarylastline]crossesanyother),thentheareanumberdisplayedismeaningless.)

{_}Toendthemeasuringprocess,andstartanothersetofmeasurements,makeafinalanchorwithadoubleclick.

{__}Measurethedistancefromtheleftmostsideofthemapwindowtotherightmost.Itshouldagreeapproximatelywiththelegendatthetopofthemap.Measuresomeotherdistances.WhatisthedistancebetweenthetwopointsfurthestapartontheGPStrack?

{__}ChangetheDistanceunitstoMilesandtheAreaunitstoSquareMiles.ChangetheNotInFeaturetypesothattheGPSpointsarejoined.(Use



View~Layer~Feature.)MeasureandrecordheretheapproximatelengthoftheoverallGPStrack.

Whatistheareaofthevolcanoinsidethetrack?_.UnderOptions~UnitschooseTrueNorth.Switchmeasuringoff,byclickingtheSelecticonnexttothe"Measure"tool.

ExaminePropertiesofGPSFixes

{__}Determinethelocation,timeofacquisition,andotherpropertiesofaparticularpoint:Choose"PositionProperties"eitherfromthe"Tool"icons(itsa"+"signwitha"?"mark)orfromthe"Data"menu.A"PositionProperties"windowwillappear.ResizethemapwindowandmovethePositionPropertieswindowsothattheydonotoverlap.(Youmayhaveto"ZoomtoExtents"soyoucanseetheentireGPStrack.)

{__}Selectapositionanywhereonthemap(butofftheGPStrack),clickingwiththeleftmousebutton.NotetheresultsinthePositionPropertieswindow.NowselectapositionontheGPStrackwiththemouse.NotethatthePositionPropertieswindowgivesmoreinformation:Youshouldseelatitude,longitude,metersabovemeansealevel,thedateandtimethepointwastaken(inlocaltime,tothenearestonethousandthofasecond),thepositionsequencenumber,andthe"status"(whetheritisa2Dor3Dpointandwhetherthefixhasbeen"corrected").(Inanyoftheworkinthistopic,ifyouseea2Dpoint,itgenerallymeansanerrorhasbeenmadeincollectingthedata.)

{__}BychoosingtheDOPstabinthePositionPropertieswindowyoucanseethePRNnumbersofthesatellitesthatwereusedtodeterminetheposition.IfthereceiverhadbeensettorecordDOPsatthetimethereadingwastaken,thosevalueswouldappearaswell.

{__}ThebuttonsatthetopofthePositionPropertieswindow("First,"">"),thelastpoint(Last),andsoon.Usethesetoolstomovethepointselection(alittle"x")alongthepathoftheGPStrack.Inwhichdirectionwastheroadtraversed?Clockwise().Counterclockwise().

{__}Aboutwhattimedidthetripbegin?________________Whatarethecoordinates?____________Recordthesameinformationfortheendofthetrip.

{__}Approximatingfromthedistancemeasurementsyoutookfromthedisplay,estimatetheaveragespeed,inkilometersperhour,ofthecarthatwascarryingtheantenna.

LookingatMoreDetail

{_}FromData~PositionProperties,selectthelocationofthebeginningpointofthetrip(useFirst).ClosethePositionPropertieswindow.

{_}Usethe"ZoomIn"tool(amagnifyingglasswitha"+"onit)topointtotheapproximateareaofthebeginningofthetripandpresstheleftmousebutton.Theareaidentifiedwillmovetothecenterofthescreenandthedistancebetweenthepointswillbemagnified.Noticethatthescaleandthedistanceacrossthewindowchange.Thedistanceacrossthewindowishalvedthescaleisdoubled.Zoominagain.Again.

{__}Noticealsothatthetrackbecomesmorejaggedasyouzoomin.Youcantellthatitconsistsofaseriesofpointsconnectedbystraightlinesegments.Usethemeasuretooltogetanideaofthesizeofthese"jags."Whiletheroadmighthavefollowedthisjaggedcourse(itdidntIwasthere)itseemsmorelikelythatthedeviationsareduetoerrorinsuccessivereadings.

{__}Nowdemagnifytheareausingthe"ZoomOut"tool(selectitfromthe"View"menu).Whichiconisequivalenttothismenuchoice?___________YoucanZoomOutbysimplyclickingintheMapwindow.Zoomoutagain.Again.

{_}Fromthe"View"menu,choose"Zoom~Extents"toreturntotheoriginalGPStrackdisplay.

{__}Repeattheabove"zooming"steps,butinsteadofsimplyclickingapoint,dragaboxaroundtheareaofinterest.Whenzoomingin,mapfeaturesinsidetheboxyoudragareenlargedtofitintothemapwindow.Whenzoomingout,theboxyoudragsuggeststheboxthatyouwanttheentirecurrentlyvisibleportionofthemaptofitinto.Thesmalleryoumakethisbox,thegreaterthedegreeof"zoomingout."Themapfeaturesshownbeforethezoomoutwillfillthisboxthosefeatureswillbecenteredatthecenterofthebox.FinishthisstepbyZoomingtoExtents.

ThefileB021602Crepresentsthefirstpartofthedrivebackfromthevolcano.ThetripbackalsoincludesthefilesB021603AandB021604A.

{_}FromthesamewindowfromwhichyouopenedVOLCANO.SSF,openB021602C.SSFwhilealsoretainingtheexisting(VOLCANO)file:Thereisatrickhere.Youmayopenseveralfilesatthesametimebyselectingthefirstonewithasimpleleftmouseclickontheicon.Addsuccessivefilesbyholdingdownthe"Ctrl"keyandclickingonthefilenameiconsthatyouwanttoadd.(Youcanalso"deselect"filenamesbyholdingdownthecontrolkeyandclickingonafilenameicon.)Onceyouhavethesetoffilesyouwantopened(twofiles,inthiscase)pressOpenandthewindowwilldisappear,leavingyouwitharecomputedmap.

{_}Getthe"Open"windowagainbyclickingonanicon.NowaddfilesB021603A.SSFandB021604A.SSF.Anothertrick:ifyouholddowntheCtrlkeybeforeyoubeginselectingfiles,thosefilescurrentlyopen,indicatedbyshading,willalsobeselectedasyouselectnewfiles.

{__}NowopenjusttheVOLCANO.SSFfilebyitselfanddisplayit.

Nextpost:ExaminingGPSData(GPSandGIS)Part3

Previouspost:ExaminingGPSData(GPSandGIS)Part1

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