GPS and GIS)
-
Upload
aremacho-erkazet -
Category
Documents
-
view
239 -
download
0
description
Transcript of GPS and GIS)
-
6/29/2015 ExaminingGPSData(GPSandGIS)Part4
http://whatwhenhow.com/globalpositioningsystemandgis/examininggpsdatagpsandgispart4/ 1/5
Subscribe
whatwhenhow
InDepthTutorialsandInformation
ExaminingGPSData(GPSandGIS)Part4
AnAerialPhotoThatCanBeUsedasaMap:TheDigitalOrthophoto
Adigitalorthophotoimageisanaerialphotograph,indigitalform,withaveryusefulspecialproperty:Ithasbeencalibratedsothatitmaybeusedasamapthecoordinatesofthemaparepreciselyspecified.Asyoumayknow,mostaerialphotographs,evenwhentakenwiththecamerapointedverticallydownward,haveconsiderabledistortion,duetoseveralfactorssuchasuneventerrainandlensdistortion.Thus,ifyoumeasurealengthonaconventionalphotographthatcorrespondstoadistanceontheground,anidenticallengthmeasuredelsewhereonthephotographusuallywillnotcorrespondtothesamedistanceontheground.Saidconcisely,astandardaerialphotographdoesnothaveaconsistentscale.Inadigitalorthophotoimage,however,objectsshownonthephotographatgroundlevelarerelatedbyapointsonobjectsabovegroundlevel(forexample,ontheroofsofbuildconsistentscale,eveniftheterrainisdramaticallyuneven.(Thelocationsofings)arenot,however,shownintheircorrectlocations.)
Digitalorthophotosmaycomeinmanyforms.Theonewelookathereiscalleda"tiff"(whichstandsfor"taggedimagefileformat."PathfinderOfficehasthecapabilityofdisplayingsuchfilesasbackgroundfiles.Theextensionoftiffnamesisusually"tif."Ifatifffileiskeyedtoageographicallocationitmaybecalleda"geotiff"geotiffscontaintheparameterstoanchortheimagetotheproperpointsontheearthssurface.Ifatiffimageiskeyedtoageographiclocationbutcontainsnogeographicparametersthenitmustbeaccompaniedbyaworldfileworldfilesusuallyendintheextension"tfw."Pathfinderofficerequiresthatatiffbeanongeotiffandthatitbeaccompaniedbyaworldfile.18
InthedirectoryByeByeSAarethefollowingfiles:
No_sa_ncr_doq.tifataggedimagefilethespecialkindofdigitizedaerialphotographthatcanbeusedasamap,showingthehighwaytheautomobilewastravelingatthetimeoftransition.ThetermDOQinthenamestandsfordigitalorthoquadranglequadrangleisjustanothertermforan"almostrectangular"map.19
No_sa_ncr_doq.tfwthe"worldfile"forNo_sa_ncr_doq.tifcontainingnumericparametersthattellPathfinderOfficewheretoplacetheimageNo_sa_ncr_doq.tif.
NoSA_Moving.SSFasubsetofafiletakeninamovingautomobilecoveringtheminutesoftransitionwhenSAwasdiscontinued.
{__}Open__:\GPS2GIS\ByeByeSA\NoSA_Moving.SSF.Representthefilewithamediumyellowline.SettheTimeZonetoEasternDaylight.Bringupthetimelineandnotethetimespanofthefile.IfyoulookatPositionPropertiesyouwillnotethatanumberoffixeshavebeendeleted.Theideawastocapturejustthetimesurroundingthetransition.
{_}PreparethemapoftheGPStracksothatthedigitalorthophotowillbeproperlypositioned:Beforetheaerialimagecanbedisplayedthegeographicparametersofthemapmustbeproperlyset.TheDOQQQQ20(standsfordigitalorthoquarterquarterquarterquadranglesinceitisonesixtyfourthofastandardUSGS7.5minutequadrangle)isintheU.S.StatePlane1983coordinatesystem,KentuckyNorthZone(1601).ThedatumisNAD1983(Conus).Thecoordinateunits,altitudeunits,anddistanceunitsareSurveyFeet.UsingtheUnitsandCoordinateSystemchoicesundertheOptionsmenu,makesuretheseparametersaresetupcorrectly.
{__}Bringupadigitalorthophotoimageasabackgroundtothefilesyouhaveselected:FromtheFilemenuselectBackground.IntheLoadBackgroundFileswindowremoveanyfilesthatshowupandthenclickAdd.Thewindowthatappears(AddBackgroundFiles)mightormightnotrepresentthefolder__:\GPS2GIS\ByeByeSA.(Ifitdoesnt,navigatetothatfolder.)Selectthefileno_sa_ncr_doq.tifandclickonOpen.Readandokayareminderifitshowsup.BackintheLoadBackgroundFileswindowreviewtheSystem,Zone,andDatumspecifications.Itprobablyappearsthatalliswell,butitmaynotbe.ClickonChangetoexamineandcorrectparameterssotheymatchtheonesgiveninthepreviousstep.BeparticularlycarefulregardingCoordinateUnits.In
ExploreNewZealand
TemukanKeindahanAlamKamidanNikmatiLiburanImpianAndadiSini
newzealand.com/NewZealand
FacebookAccountSignUp
TheWorld's#1OnlineCommunity.JoinforFree&
EnjoytheBenefits!facebook.com
-
6/29/2015 ExaminingGPSData(GPSandGIS)Part4
http://whatwhenhow.com/globalpositioningsystemandgis/examininggpsdatagpsandgispart4/ 2/5
KentuckytheyareinSurveyFeet!OkaytheCoordinateSystemwindow.OkaytheLoadBackgroundFileswindow.AnimageshouldappearintheMapwindow.
{__}MakethemainPathfinderOfficewindowoccupythefullscreen.MaketheMapwindowwideasinFigure38,soyoucanhavePositionPropertiesandTimeLineupalso.ZoomuponthepartoftheyellowtrackthatcrossestheDOQ.LookattheGPStracksthatrepresentthepartofthetriponthedividedhighwaythattookplaceduringthetransitionfrom"SAon"to"SAoff."Firstthetrack,comingfromthewest,iswayofftheroad,thenyouseesomejaggedspikesthatoccurredprobablyduetothetransition,andfinallythetraceisatleastintherightofwayofthehighway.WithPositionpropertiesyoucanascertainthatthetransitionwascompletedatabout13secondsafter12:01AMon2May2000.
PROJECT3EYourData
NowthatyouhaveagoodideaofhowtousePathfinderOfficetodisplayandanalyzedatatakenwithaGPSreceiver.
{__}Beforebeginningthecomputerwork:
Unlessyourinstructortellsyouotherwise,youmustusethemachineontowhichyouloadedyourdata
Figure38.Watchselectiveavailabilitygoaway.
RecallthenameoftheProjecttowhichyoutransferredyourdata.ItisprobablyDATA_yis(where"yis"indicatesyourinitials).Thefolderinwhichyouwillworkis__:\GPS2GIS\DATA_yis.
Bringwithyouthefullname(s)ofthefile(s)youcollected.AlsohavewithyouthevaluesyoucalculatedbyhandinProject1C.
Bringthedetailedmap(s)ofthearea(s)whereyoutookthedatasoyoucancomparewhatappearsonthescreenwiththefeaturesshownonthemap.
{__}Ifnecessary,startthePathfinderOfficesoftware.SelectProjectsintheFilemenu.MakesurethattheProjectnameis"DATA_yis."ClickontheOpenFoldericonontheProjecttoolbar.Clickthe"Details"buttontoseethedatesonthefilesandfolders.Reviewthefilesthataretheretobesurethatyouareintherightfolder.YoushouldseeaBackup,Base,andExportfolderaswellasyourfiles.Select,withasingleclick,thefirstofthefilesyoutook.Lookattheinformationaboutthatfileatthebottomofthewindow.Closethewindowwithoutopeningthefile.
{__}ExaminethemapyouusedinProject2Atodeterminethecorrectunits,coordinatesystem,anddatumtouse.Setupthesoftwarewiththeseparameters.
{_}Therepresentationnowonthescreenshouldbeofthepoints(fixes)youcollected,connectedinthetimeorderinwhichtheywereloggedbythereceiver.
Thefollowingstepsassumethatyoutookpointdata.
{__}YousettheGeoExplorerroveroptionsbeforethatsessionaccordingto:
-
6/29/2015 ExaminingGPSData(GPSandGIS)Part4
http://whatwhenhow.com/globalpositioningsystemandgis/examininggpsdatagpsandgispart4/ 3/5
Coordinates~Deg&Minutes(anddecimalfractionalpartsthereof)
Datum:(settoyourmap)
Units~Custom~Distance:(settoyourmap)
Units~Custom~AltitudeUnits:(settoyourmap)
Units~Custom~AltitudeReference:Geoid(MSL)
Date&Time~SetLocalTime:(adjusttolocaltime)
SetthePathfinderOfficeoptionstotheequivalents.
{__}SelectPositionProperties.Clickonafixthatistowardthemiddleoftheclusterofpoints.Readitslocationatthebottomofthescreenandwriteitdownhere.
Latitude_____________
Longitude____________
Altitude_
Isitaboutwhereyouexpectedittobe?CompareitscoordinatevaluesagainsttheaveragedvaluesinPROJECT1Cthatyouwrotedownatthattime.
WecouldmakeaPoint_genericfile(averageallthefixesintoasinglepoint)aswedidinProject3B,butletslookatanotherwayofgettingtheaverage.ThedatacollectedbytheGPSreceiveranddownloadedintothemachinetaketheformofrecords,whicharenumberedstringsoftext.AgivenGPSfilewillhavequiteafewrecordsatleastoneforeveryfixtaken,andusuallyalotmore.YoucanlookattheserecordswithaTrimbleUtilitycalledtheSSFRecordEditor.WhentheRecordEditorisinvokeditautomaticallyaveragesthecoordinatesofallthefixesandappendsadditionalstatisticalrecordstothefileattheend.InthestepbelowyouwillopenthefileintheRecordEditor,lookbrieflyatafewrecords,andthenreadthecoordinatesofthe"average"point.
{__}Gointothefilemenuandpick"Close"toclosethecurrentfile.(TheRecordEditorwillnotcalculatestatisticsonafileifthefileisopen.)Youhavealreadysetuptheproperparametersofdatum,coordinatesystem,andunits.IntheUtilitiesmenuselectOther,thenSSFRecordEditor.Theappropriatewindowwillcomeup.UnderFileinthatwindowclickOpen.Youshouldthenbeabletoselectthefileyouhavebeenworkingwithfromthewindowthatshowsup.ClickOpen.MaketheSSFRecordEditorwindowoccupythefullscreen.
Theresultingwindowisdividedintotwoparts.(Youcanvarythepositionofthedividinglinebetweenthembydraggingitwiththemouse"Split"intheViewmenualsoworks.)Inthetoppartaretherecordsofthefile,beginningwithaheaderrecordwhosethreeletterdesignationisHDR.TheHDRrecordishighlighted.Inthelowerpartofthewindowaredetailsinamorereadableformatrelatingtothathighlightedrecord.Also,somerecords,likeHDR,containinformationnotshownontheupperpartofthewindow.Thisinformationappearsinthebottomportionofthewindow.Makesurethatthebottompartofthewindowislargeenoughtoseeallthetextlines.PleaseseeFigure39.
MostSSFfileshaveseveraltypesofrecords.Shortlyyouwillseethattowardthemiddleofthefileyouwillfindposition(POS)recordsthattellyouthetimeandpositionofeachseparatefix.Attheendofthefilearestatisticsrecords(STS).
{__}LookattheinformationintheHDRrecord.Thenusethedownarrowkeyand/orPageDowntolookatrecordsfurtherdowninthefile.Finally,dragtheverticalslidertothebottomsothattheSTSrecordsthatwereaddedtotheendofthefileshowup.Usethe"uparrow"keytoselectthe"LatitudeStat"record.Writethecoordinatesofthatandthefollowingrecordshere.
MeanLatitude
MeanLongitude:
MeanAltitude:21
{_}FromtheFilemenuexittheSSFRecordEditor.
{__}Someofthequestionsbelowhaveseveralblanks.AssumingyoutookdataforbothPROJECT1BandPROJECT2Ainthesamelocation,recordthecalculationsyoumadeinPROJECT1C.
-
6/29/2015 ExaminingGPSData(GPSandGIS)Part4
http://whatwhenhow.com/globalpositioningsystemandgis/examininggpsdatagpsandgispart4/ 4/5
CustomSearch
Figure39.FindingstatisticsfromtheRecordEditor.
{__}Setupthedatum,coordinatesystem,andunitstocorrespondtothoseofthemapyouusedinPROJECT2B(whereyoumovedtheantennaalongapath).
{__}BringinthefileofPROJECT2Banddisplaythepathyoutookwhilemovingtheantenna.Nowqueryvariouspointsonthedisplayandcomparetheircoordinateswiththoseonthemap.Doesthedisplaycorrespondtotheactualpathyoutook?
{__}AddthefilethatcontainsthefixesyoucollectedinPROJECT2A.Arethetwositesinthecorrectrelativeposition?Ifnot,youmaybeusingdifferentprojections,differentdatums,ordifferentcoordinatesystems.
Nextpost:DifferentialCorrection(GPSandGIS)Part1
Previouspost:ExaminingGPSData(GPSandGIS)Part3
0
RelatedLinks
GlobalPositioningSystemandGISBasicConcepts(GPSandGIS)Part1BasicConcepts(GPSandGIS)Part2BasicConcepts(GPSandGIS)Part3BasicConcepts(GPSandGIS)Part4BasicConcepts(GPSandGIS)Part5
::SearchWWH::
Search
AdsbyGoogle
JavaPDFThePoliceExamPDFDocument
AdsbyGoogle
PDFDocumentACMotorControl3PhaseInductionMotor
-
6/29/2015 ExaminingGPSData(GPSandGIS)Part4
http://whatwhenhow.com/globalpositioningsystemandgis/examininggpsdatagpsandgispart4/ 5/5
HelpUnprivilegedChildrenCareersPrivacyStatementCopyrightInformation