Overview of post-processing with GLOBKgeoweb.mit.edu/~floyd/courses/gg/201705_Bristol/pdf/22... · 2017. 5. 2. · Data Editing • To account for temporal correlations in time series

Overviewofpost-processingwithGLOBK

M.A.FloydMassachusettsInstituteofTechnology,Cambridge,MA,USA

SchoolofEarthSciences,UniversityofBristolUnitedKingdom2–5May2017

MaterialfromT.A.Herring,R.W.King,M.A.Floyd(MIT)andS.C.McClusky (nowANU)

http://web.mit.edu/mfloyd/www/courses/gg/201705_Bristol/

GLOBKOverview

• HerewereviewthemainfeaturesofGLOBKandGLRED.

• Topics:– Programflow– Kalmanfiltering– GLOBKfilesandestimationrules– GLORGprogram/function:Defineoriginplusotherthings

– Outputoptions– Flowofprograms

2017/05/03 Overviewofpost-processingwithGLOBK 1

GLOBKPurpose• GLOBKisasuiteofprogramsdesignedtocombinegeodeticresults

together.GPSphaseprocessingcantakeaconsiderabletimeandGLOBKprovidesafastmethodformakelargenetworksolutions,combiningmanydaystoyearsofdatatogetherandstudyingalternativeparameterizationandreferenceframesforthevelocitiesofsites.

• GLOBKusesasdatainput,quasi-observationfilescalledbinaryh-fileswhichcontaingeodeticsolutionswithlooselyconstrainedfullcovarianceinformation.Thesefilescangeneratedfromgamit solutionsorSINEXfiles.

• GLOBKisasmoothingKalmanfilterandcanincorporaterandomwalkprocessnoiseinitsestimation(methodforaccountingfortemporallycorrelatednoiseintimeseries).

• Itstwomainusesaretogeneratevelocityfieldestimatesandtimeseriesinawell-definedandoftendifferentreferenceframes.(ItcanalsobeusedtomergelargenetworksofGPSsites).


CommonapplicationsofGLOBK• Repeatabilityanalysis(glred )

– individualsessions– combineregionalandglobalfilesfororbitcontrolandreference

frame(orbitcontrolisnotsoimportantanymore;IGSorbitsareverygoodapriori)

• Combinesessionstogetaveragepositionoversurvey– connectsstationsobservedseparately– reducesnumberofh-filestobeusedforvelocities

• Combineaveragedpositionstoestimatevelocities– and/orearthquakeoffsetsandpost-seismicmotion

• Whenglobk isruninparallelinthesamedirectory,careshouldbeusedinscratchfilenames(discussedlater)


Processingstages• HTOGLBgeneratesinputbinaryh-files.• GLOBKhasdistinctmodulesthatareused:

– Initialization:Headerinformationfromthebinaryh-filesarereadtodeterminethenatureofthesolutionsi.e.,parametersinthestatevector,allsitenamesaccountingforoffsetsandearthquakesetc.

– ForwardKalmanfilter:Binaryh-filesarecombinedtogeneratesolution.Normallymostparametersarelooselyconstrained.

– Possiblebackwardssmoothingfilter(notthatcommon)– Simpleoutputofthesolution(programGLOUT:generates.prt file)– Referenceframerealizedsolutionandpost-solutionconstraints.Generates

.orgfile.ProgramGLORGcanbeusedseparatelyformultiplerealizationsandconstraints.

– Savingbinaryversionofsolutionforadditionalprocessing(out_glb andGLSAVEprogram).

• ModulesinGLOBKcanbecalledwithinGLOBKassubroutinesorrunexternallyasstand-aloneprograms(programnamesarelowercase)



GLOBKFunctionandFileFlowhtoglb:TranslateGAMITh-filesto(e.g.,hemeda.10256)toglobk

h-files(e.g.h1009131200_emed.glx

[h-filelist].gdl àglobk_comb.cmditrf08_comb.apritrf08_comb.eq

GLOBK

à globk_comb.prtglobk_comb.log[h-filelist].com(binarysolutionfilethatcanbeusedinglorg)

comb.com àglorg_comb.cmdItrf08_comb.aprstab_site [list]

à globk_comb.org

GLORG

Namesoffilesherecanbechosenarbitrarily.

GLOBKcommandfiles• GLOBKiscontrolledbyacommandfilethat“instructs”theprogramwhat

todo.• Thecommandfilecontainthefollowingclassesofcommands:

– Estimationcommand:Tellsglobk whattoestimateandconstraintsonapriorivaluesandtemporalbehavioroftheparameters.apr_xxx andmar_xxxcommands.

– Aprioriinformationcommands:Coordinates,discontinuitytimes,selectionofsites

– Output(typesandfiles),andcontrolcommands(e.g.,torunglorg)• GLORG(post-processingprogram/module)alsohasitsowncommandfile.• Thesimplestglobk commandcanhaveoneline:

apr_neu all101010000butingeneralhaveseveralothercommonscommands(seeexamplesin~/gg/tables/globk_xxxx.cmd and~/gg/tables/glorg_xxxx.cmd


GLOBKfilenameconventions• GLOBKusesarbitraryfilenamesbuttherearesomeconventionsused:– Binaryh-filesfromhtoglb:.glx isbiasfixed,.glr isbiasfree(normallynotused)

– Listofbinaryh-filestoprocess:.gdl extent– GLOBKandGLORGcommandfiles:globk_<type>.cmd andglorg_<type>.cmd

– Outputfiles:printfile(noglorg referenceframe).prt(oftennotoutput);glorg output.org;logfile.log

– Aprioricoordinatefiles:.apr– Earthquakeandrenamefile:.eq– Listsofstabilizationsites(usedwithsourcecommand):.stab


KalmanFiltering• Equivalenttosequentialleast-squaresestimationbut

allowingforstochasticprocesses,usuallya1st-orderGauss-Markovprocess

• GLOBKallowsarandomwalkforcoordinates,EOP,networktranslationandscale,andsatelliteparameters;variancegrowslinearlywithtime

• BecauseaKalmanfilterworkswithcovariancematrices(ratherthannormalmatrices),allparametersmusthaveaprioriconstraints(usuallyloose)

• SeeHerringetal.[1990]andDongetal.[1998]foramorethoroughdescriptionasappliedtogeodeticanalysis


GLOBKStructuralConfusions• globk andglred arethesameprogramwith(slightly)

differentwaysoftreatingtheh-file(gdl )list:– globk:allh-filesincombinedinasinglesolution– glred:eachh-filegeneratesaseparatesolution(unlessfollowed

bya+) .glred isasmallprogramthatgeneratessub-set.gdlfilesandrunsglobk.

• Twotypesofsolutionfiles:– h-filesforsavingandexternalexchange(backwardcompatible) – com/solfileisinternal,formatchangeswithversions

• glorg calledbyglobk/glred orrunseparatelytoapplygeneralizedconstraintstosolutionandestimateplaterotations.Com_file commandmustbeusedinglobkcommandfileforglorg torunbyitself.


GLOBKfiles• Usersupplied

– commandfiles(mayinclude‘source’files) – gdl listofh-files– binaryh-files(createdfromSINEXorGAMITh-) – apr file(s)(optionalbutrecommended) – EOP(in_pmu file,optionalbutrecommended) – eq_file (optional,butmustappearattop)

• Generatedbyglobk– .srt,.com,.sol,.svs (allexcept.solmustbenamedandcommandsneedtobetopofglobk commandfile)

• Outputfiles– screen,log,prt,organdoutputh-file


GLOBKfilehandling• log,prt,orgfilesareconcatenated,soshouldberemovedorrenamedunlessyouwantthemtogether(e.g.glred) .The‘eras’optioncanbeusedintheprt_opt andorg_opt commandintheglobk commandfiletoerasethesefiles(shouldnotbeusedwithglred).

• com,srt,solfilesareoverwritten;com/solshouldnotberenamedsincetheoriginalsolfilenameisimbeddedinthecomfile.

• Automaticnamingusingwild-cardsisavailableforcom,srt,sol,org,andoutputh-files(i.e.,nameuseddependsonnameof.gdl file;neededforparallelprocessing.)


Estimationcommandsrules• Foraparametertoestimatedinglobk,apr_xxx commandmustbe

usedwherexxxisaparametertype(e.g.,neu,svs,wob,ut1,atm) • Ifaparameterisnotmentioned,itdoesnotappearinthesolution,

butifitappearsintheh-file(i.e,estimatedinGAMIT),itsuncertaintyisimplicitintheglobk solution;e.g.,iforbitsareestimatedinGAMITandyouwantthemconstrainedinglobk,useapr_svs.Ifapr_svs isnotused,orbitsareleftconstrained.

• Ifzerogivenasapriorisigma,thenparameterisnotestimated(effectivelyleftunconstrained)

• Toforceaparametertoit’sapriorivalue,useFastheapriorisigma• Parametersestimatedinglorg mustbekeptlooseinglobk ;if

rotationorscaleisnotestimatedinglorg,itmustbetightlyconstrainedinglobk


EarthOrientationParameters(EOP)

• Normallyusedintwoforms:– Globalnetworkofstations(allowsrotationinglorg)

apr_wob 101011apr_ut1101

– Regionalnetwork(constrained).Whenconstrainedthiswaysystemisnotfreetorotatesoxrot,yrot,zrot shouldnotbeusedinpos_org command(seepos_org inglorg ) apr_wob .2.2.02.02apr_ut1.2.02

• Inmanyanalyses,theglobalformisusedevenforregionalnetworksinordertoallowrotationestimationinglorg.(Careisneededifnetworkisnotsurroundedbystationswithwelldefinedmotions).


DataEditing• Toaccountfortemporalcorrelationsintimeserieswetypicallyuse

random-walk(RW)processnoisewiththemar_neu command(unitsm2/yr )

• Typicalvaluesare2.5E-8(0.5mmin1yr)to4E-6(2mmin1yr)– mar_neu all2.5E-82.5E-82.5E8000– mar_neu chdu 4E-64E-64e-6000

• Thesh_gen_stat commandcanusedtogenerateprocessnoiseestimatesprovidedsufficientlylargenumberofpositionestimatesareavailable.

• Todown-weightnoisysegmentsorequalizecontinuousandsurvey-modedatainacombinedh-file,canaddrandomnoise(unitsarem) – sig_neu all.001.001.003– sig_neu ankr .005.005.02020021010020021130240– sig_neu EMED0504.010.010.1

• Toremoveanoutlier,candown-weightseverelyorrename– sig_neu ankr .1.1.12002101002002101240– renameankr_gps ankr_xcl 2002101002002101240(eq_file )


GLORG

• Invokedbyglobk toapplygeneralizedconstraintsafterh-filesarestackedandloosesolutionperformed;canberunasaseparateprogramusingthecom/solfilesfromglobk

• AlsoallowslinkingofparametersandestimationofEulerpoles

• Parametersestimatedinglorg mustbekeptlooseinglobk (coodinates,EOP,scale)

• GLORGisusedtodefineandrefinethereferenceframeforGLOBKsolutions.


InvokingGLORGfromglobk commandfile

• Theglobk commandfilecontainscommandsthatcauseglorg torunwhenglobk completesthesolutioncombination:– org_cmd <glorg commandfilename>---invokesglorg

– org_opt <optionsforoutput>– org_out <outputfilename>:Normallynotusedbecausenamewillbegeneratedfromprt filenameintheglobk runstring.

• Iforg_out isnotgiventhentheextentontheprintfilenameisreplacedwithorg


GLORGCommands• apr_file – Neednotbethesameasforglobk;needstocontain

valuesonlyforsitesusedforstabilizationandsitesforwhichcoordinatesorvelocitiesareequated

• pos_org,rate_org – Controlwhatparametersareestimatedinstabilization– xtran ytran ztran – allowstranslation(apr_tran inglobk ifGAMIT

BASELINEchoiceofexperiment)– xrot yrot zrot – allowsrotation– scale– allowsrescalingofsystem(ifused,estimatescaleinglobk;

apr_scale andpossiblymar_scale) • cnd_hgtv – Controlrelativeweightsofheights(variances,nominally

10butincreasingvaluewillreduceheightseffectinghorizontalpositionestimates;1000isgoodforthis)

• stab_ite – #ofiterationsandsigma-cutoff toremoveasite• stab_site – Listofsitestouseinstabilization


ControllingPrintOutput• crt_opt,prt_opt,org_optspecifyoutputoptionsforscreen,printandorg

files• globk/glorghelpgivesalloptions,mainonesare:

– ERAS-- erasefilebeforewriting(normallyfilesappended) – NOPR-- Donotwriteoutput(e.g.,forglobkwheninvokingglorg) – BLEN-- Baselinelengths– BRAT-- baselinerateswhenvelocitiesestimated– RNRP-- generatesreportsondifferencesinparameterestimatesafter

renames.– FIXA-- makesaprioricoordinatesandvelocitiesconsistentwhenequatesare

usedinglorg(cansometimesfailincomplicatedrenamescenarios--bestifapr_fileisprovidedwithconsistentvalues)

– VSUM-- Lat/longsummaryofvelocity(neededtoplotvelocities) – PSUM-- Lat/longpositionsummary– GDLF--Includelistofhfilesandchi**2incrementsfromrun– CMDS-- Echosglobkcommandfileintooutputfile


ProgramFlow• Readalltheh-fileheaderstodeterminetheircontents(sites,other

parameters,epochrange)• Applyrenamesasrequestedintheeq_file• Sorttheh-filelistforwardorbackwardintime(srt_dir )• InitializetheKalmanfilterwiththeaprioriconstraints(apr_xxx ) • Readintheh-files,oneatatime,arunsequentialKalmanFilter.Compute

thechi2increment,coordinateadjustment,androtationimpliedbythenewdata;ifwithintolerance(max_chii ),updatethesolutionandwritethechi2incrementtothelogfile

• Writethesolutiontothesol_file andprt file(andoptionallytoanewh-file)

• Optionallyinvokeglorg toapplygeneralizedconstraints– Applytheconstraints(iterative“stabilization”) – Applylinkageofparameters(equate,constrain,force),computingthechi2

incrementforeach– Estimateplaterotations(platecommand)– Writethesolutiontotheorgfile(glorg prt file)


ThingsGLOBKcannotdo

• Repairmistakesinoriginalanalysis– cycleslips– wrongantennaphasecentermodels

• Resolveambiguities– (wouldmakefilestoolarge)

• Overcomenon-lineareffects– AsinGAMIT,adjustmentsmustbelessthan~30cm

• ButGLOBKcandeletestations– canhelpavoidcontaminatingsolution


AprFilesinGLOBKProcessing• GAMIT

– 10maccuracyforallsitesforcycle-sliprepair– <30cmfinaladjustmentforlinearity(1stsolutionguarantees) – ~5cmaccuracyinconstrainedsite(s)forambiguityresolution

• globk– Ifinvokingglorgforreferenceframe,apr_fileusuallyoptionalin

globk– Ifnotinvokingglorg,needaccurateapr_fileentriesfor

constrainedsites– Forcomplicatedrenamesandequates,apr_filemaybeneeded

inglobk• glorg

– Apr_fileneedscoodinatesonlyforreferencesitesandequates


Whatcangowrong?• globk

– H-filesnotused:removedautomaticallyforhighchi2,coordinateadjustment,orrotation(max_chii command)

– Highchi2increment:inconsistentdata.Canbeanissuewhenestimatingorbits(RELAXmode)ifMITGLXfileusedifferentmodelling(e.g.Albedo,gravityfield)

– Station“missing”:notpresentinh-fileorrenamedout(useglist ) • glorg

– Stabilizationfails:too-fewsitesinstabilization– Largeuncertainties:poorstabilization– Too-smalluncertaintiesforsomestabilizationsites:rotation

parametersabsorbingcoordinateadjustment– Highchi2inequate:inconsistentdata– Wrongvelocityforequatedsites:unmatchedapriori


Associatedprograms– htoglb – Translatesvariousascii solutionfilesintoGLOBKh-files(GAMITh-files,SINEX)

– glbtosnx -- GeneratesSINEXfilesfrombinaryh-files– glist -- liststhecontentsofaseriesofh-files– hfupd -- Updatesbinaryh-filesforchangesinstation.info orsinex headerfile(distributedbyIGS)

– ensum,enfit,tscon,tsfit -- timeseriesanalysis(batch)

• Matlab derivedprograms(interactive):– velview -- displaysandanalyzesvelocityfields– tsview -- displaysandanalysestimeseries.


Summary• GLOBKhasmanyfeaturesandduetoitsevolution,there

areoftenmultiplewaysofdoingthesameorsimilarthings.• Thereisextensivehelpinthe~/gg/help/directoryand

discussioninthedocumentation.• GLOBKiswhereallthemajoranalysisdecisionsaremade

andhencecanbequitecomplexforlargeanalyses.• Experimentationandtestingyourideasofhowdifferent

optionseffecttheresultsisonethebestwaystolearnthesoftware(e.g.,whathappenstoposition/velocityestimatesiftheapr_tran commandisaddedtotheglobk commandfile?Howdomyestimatesanduncertaintieschangeiftheapr_neu andmar_neu commandsarechanged?


Documents

Overview of post-processing with GLOBKgeoweb.mit.edu/~floyd/courses/gg/201705_Bristol/pdf/22... · 2017. 5. 2. · Data Editing • To account for temporal correlations in time series