InternationalGNSSService(IGS)

http://www.igs.org

ChairoftheGoverningBoard:GaryJohnston

(Australia)

DirectoroftheCentralBureau:RuthNeilan(USA)

ApplicationsoftheGlobalNavigationSatelliteSystems(GNSS)toEarthSciencesandtechnologyarenumerousandgrowing.TheInternationalGNSSService(IGS),avoluntaryfederationofgovernmentagencies,universitiesandresearchinstitutions,combinesGNSSresourcesandexpertisetoprovidethehighest–qualityGNSSdata,products,andservicesinordertosupporthigh–precisionapplicationsforGNSS–relatedresearchandengineeringactivities.TheIGShasbeenaserviceoftheIAGsince1994.

OverviewTheIGShascontinuedtosupportscientificandotherGNSSusersthroughthe2015-2017reporting

period.TheIGSprovidesessentialproductsthatcontributetotherealizationofITRFandenablevery

highaccuracypositioningusingGNSStechnologiesforscientific,andawidevarietyofotheruses.The

Servicealsoprovidesanumberofexperimentalproducts,inacontinuousefforttoencourage

technologicalandanalyticalimprovement.IGScontinuestorefinetheaccuracyandconsistencyofits

productsbyanongoingprocessofbothtechniqueimprovementandreprocessingofpastdatasetsin

ordertoachievethehighestqualityresults.

TheIGScontinuestoadaptandcontributetoadvancesintechnology,includingongoingandincreased

effortsfortransitioningtoamulti-GNSSservice,aswellasadvancingreal-timeapplications.Re-tooling

andmodernizationofcapabilities,aswellasdevelopingandextendingrelevantstandards,havealso

beensignificanteffortswithintheIGS.

Inadditiontomanytechnicalachievements,theIGScontinueswithproactiveeffortstosustainablymaintainanddeveloptheIGSorganizationandimproveitsmanagement.Startingwherethe2013-2016StrategicPlanended,acomprehensiveusersurveyandstrategicplanningprocesstookplaceinlate2016andearly2017.Theresulting2017StrategicPlanhasbeendevelopedinresponsetoboththeuser

andcommunitysurveyresponsesaswellascontinuingkeyelementsofthepreviousstrategicplan’sgoalsandobjectives.ItalsoaimstorecognizetheextensivecontributionoftheIGSparticipants,andtoencouragestrongengagementwithabroaderstakeholdersetthatnowrelyimplicitlyonIGSproductsandservices.

TheIGSTermsofReference,aswellastheassociatemembership,havebeenreviewedannuallybythe

GoverningBoardandrelevantcommitteessince2011,withupdatestobothinthelastyear.Allcurrent

IGSorganizationaldocumentsandcomponentmembershiprostersaremaintainedintheIGSKnowledge

Basewebsite:http://kb.igs.org/.

Byworkingwithinthesciencecommunitythrough(IAG/IUGG/ICSU)andtheinter-governmentalcommunitythroughICG/UNGGIM/USPNTABandothers,theIGSGBisensuringtheIGSretainsitsstronglevelofrelevanceandimpact,andthereforesustainability.

EventsandMilestonesMGEXExperimentTransitiontoServiceandPilotProjectThesuccessoftheMGEXexperimenthasdemonstratedtheinevitabilityofatransitionoftheIGStoafullmulti–GNSSService.Accordingly,theGoverningBoarddecidedtoacknowledgethisbyterminatingthe“experiment”statusandmoveMGEXtothestatusofaPilotProject.Continuedeffortsarerequiredtonegotiateaccesstosatellitespecificinformationfornewsatellitesfromsystemproviders,allowingformorerealisticmodelsofsatellitebehaviortobedevelopedandutilizedbytheIGSAC’s.WuhanDataCenterIn2015theGoverningBoardendorsedtheproposalbyWuhanUniversity,China,tobecomeanIGSGlobalDataCenter.TheWuhanDataCenteroffersaccesstothefullcollectionofIGSdataandproductstoanyuserglobally,especiallythosewithintheAsiaPacificRegion.ImportantlythedatacentergivesdirectaccesstotheIGSdataholdingstotheverylargeresearchsectorwithinChina.

NewAnalysisCenterCoordinatorIGShascontinuedwithaveryexcitingworkprogramandlistofachievementsfromtheIGSparticipantsandcontributingorganizations.TheroleofAnalysisCentreCoordinator(ACC)isnowdistributedacrosstwocenters,GeoscienceAustraliaandMIT,intwocontinents,hemispheresapart,usingcombinationsoftwareoperatingonCloudcomputingservices(AmazonWebServices).

IGS2016WorkshopinSydney,Australia

In2016,theIGShaditsfirstworkshoptobeheldoutsideofNorthAmericaorEurope,withtheSydneyWorkshopheldinFebruary2016attheUniversityofNewSouthWales.Thisworkshop,thefirstinSouthEastAsia,andthefirstinthesouthernhemisphere,signaledthestrongerinvolvementofBeiDouandQZSSintotheIGS’sGNSSfuturesandfeaturedkeynotepresentationsfromToddHumphreys(UniversityofTexasatAustin),JanWeiss(UCAR),andJohnChurch(CSIRO),aswellasover50plenarypresentationsand57posters.Keynotes,presentations,andpostersmaybeviewedontheIGSwebsite:http://www.igs.org/presents/workshop2016.

IGS-UNICGCollaborationonGNSSMonitoringandAssessmentIGSplayedakeyroleinformingtheUnitedNationsInternationalCommitteeonGNSS(ICG)InternationalGNSSMonitoringandAssessment(IGMA)TaskForce,andInternationalGNSSService(IGS)JointGNSSMonitoringWorkingGroupmetconcurrenttotheSydneyworkshop.TheCallforProposalsforparticipationintheIGS/ICGjointMonitoringandAssessmentprojectisapragmaticexampleoftheIGSbeingflexibleenoughtorespondtostakeholderrequirements.ThatprojectaimstoutilizeexistingskillswithintheIGScommunitytoserviceanewusercommunityasanextensiontoourcurrentroleofprovidingworldclassGNSSexpertise.TheCallforParticipationhadastrongresponseincludingaproposalfromESAtoundertaketheMonitoringandAssessmentACCfunction.ImportantlythisnewjointprojectensurestheIGScontinuestohavestronginfluencewithGNSSsystemproviders.ThisstrongrelationshiphasbeendevelopedovermanyyearsbyIGSparticipationintheICG.

Publications,Presentations,OutreachComprehensivelistsofIGSpublicationssince2015,aswellaspublicationsreferencingIGSinthat

timeframe,maybefound,organizedaccordingtoIGScomponent,inthe2015TechnicalReportaswell

asthe2016TechnicalReport.

Figure1:TheIGSAt-a-Glance

IGSStructureTheIGSisaself-governedfederationof388contributingorganizationsfrom118countriesaroundthe

worldthatcollectivelyoperateaglobalinfrastructureoftrackingstations,datacentersandanalysis

centerstoprovidehighqualityGNSSdataproducts.TheIGSproductsareprovidedopenlyforthe

benefitofallscientific,educational,andcommercialusers.TheIGSisgovernedbyaninternational

GoverningBoard(Table1)thatiselectedbydesignatedAssociateMemberswhorepresenttheprincipal

IGSparticipants.ExecutivemanagementoftheIGSiscarriedoutbytheCentralBureau,asis

coordinationoftheIGSTrackingNetworkandmanagementoftheIGSwebportalthatprovides

centralizedaccesstoIGSproductsandinformation.IGSproductsaregeneratedbycombiningresults

fromdifferentAnalysisCentersunderthedirectionoftheAnalysisCoordinatorandspecificProduct

Coordinators.IntroductionofnewproductsandspecifictechnicalissuesareaddressedthroughPilot

ProjectsandWorkingGroupsoftechnicalexperts(Table2).TheIGSorganizationisdepictedinFigure2.

Table1:IGSGoverningBoardMembers,asofMay2017

Status First Last Affiliation Country Role ServiceYears

EC-V Gary Johnston GeoscienceAustralia Australia BoardChair 2010-2018

Michael Moore GeoscienceAustralia Australia AnalysisCenterCo-Coordinators

2016-2019

EC-V Chris Rizos UniversityofNewSouthWales Australia IAGappointed 2004-2019

V Carine Bruyninx RoyalObservatoryofBelgiumObservatoireRoyaldeBelgique(ORB)

Belgium IGSNetworkRepresentative

2011-2017

Ken MacLeod NaturalResourcesCanada/RessourcesnaturellesCanada

Canada RINEX-RTCMWorkingGroupChair

2012-2019

V Felicitas Arias BureauInternationaldesPoidsetMesures

France BIPM/CCTFRepresentative

2005-Present

V Zuheir Altamimi InstitutNationaldel'InformationGéographiqueetForestière

France IAGRepresentative 2011-2019

V Paul Rebischung InstitutNationaldel'InformationGéographiqueetForestière

France IGSReferenceFrameCoordinator

2017-2020

V Laura Sanchez DeutschesGeodätischesForschungsinstitut

Germany NetworkRepresentative

2014-2017

V Mathias Fritsche DeutschesGeoForschungsZentrum(GFZ)

Germany AnalysisCenterRepresentative

2015-2019

Oliver Montenbruck DeutschesZentrumfürLuft-undRaumfahrte.V.

Germany Multi-GNSSWorkingGroupChair

2012-2020

Tilo Schöne DeutschesGeoForschungsZentrumPotsdam

Germany TIGAWorkingGroupChair

2001-2020

V Loukis Agrotis ESA/EuropeanSpaceOperationsCentre

Germany Real-timeAnalysisCoordinator

2014-2017

V Werner Enderle ESA/EuropeanSpaceOperationsCentre

Germany Appointed(IGS) 2016-2017

Ignacio Romero ESA/EuropeanSpaceOperationsCentre

Germany InfrastructureCommitteeChair

2010-2017

Axel Ruelke FederalAgencyforCartographyandGeodesy(BKG)

Germany Real-timeWorkingGroup,Chair

2016-2019

V Satoshi Kogure JapanAerospaceExplorationAgency(JAXA)

Japan Appointed(IGS) 2014-2017

Andrzej Krankowski UniversityofWarmiaandMazuryinOlsztyn

Poland IonosphereWorkingGroupChair

2007-2020

EC-V,IR

Rolf Dach AstronomicalInstitute,UniversityofBern

Switzerland AnalysisCenterRepresentative

2015-2018

Arturo Villiger AstronomicalInstitute,UniversityofBern

Switzerland AntennaWorkingGroupChair

2017-2020

Stefan Schaer FederalOfficeofTopography-swisstopo

Switzerland Calibration&BiasWorkingGroupChair

2007-2020

Marek Ziebart UniversityCollegeLondon UK AnalysisCenterCoordinator

2011-2020

EC-V Ruth Neilan IGSCentralBureau,JetPropulsionLaboratory

USA DirectorofIGSCentralBureau

1994-Present

Table2:IGSWorkingGroupsandProjects

Antenna

CoordinatesresearchinthefieldofGNSSreceiverandsatelliteantennaphasecenterdetermination

ArturoVilliger,Chair

BiasandCalibration

UpdatesvariousbiasvaluesandrelatedauxiliaryinformationforconsistentGNSSanalysis(productgeneration),e.g.,differentialcodebiases;definesstandardsanddataexchangeformatsinthefieldofGNSSbiases

StefanSchaer,Chair

ClockProducts

Globalsub-nanosecondtimetransfer,andIGStime-scale,jointlywiththeBureauInternationaldesPoidsetMesures(BIPM)

MichaelColeman,Chair

DataCenter

CoordinationamongIGSdatacentersandsupportforincreasingnumberofproductsandreal-time

CareyNoll,Chair

IGMAMonitoring

UnitedNationsInternationalCommitteeonGNSS(ICG)InternationalGNSSMonitoringandAssessment(IGMA)TaskForceandInternationalGNSSService(IGS)JointGNSSMonitoringWorkingGroup

UrsHugentobler,Chair

Ionosphere

Ionosphericscienceresearch,globalionosphericmapsAndrzejKrankowski,Chair

V Shailen Desai JetPropulsionLaboratory USA AnalysisCenterRepresentative

2012-2019

V Richard Gross JetPropulsionLaboratory USA IERSRepresentative 2015-2019

V Thomas Herring MassachusettsInstituteofTechnology(MIT)

USA AnalysisCenterCoordinator

2016-2019

Carey Noll NASAGoddardSpaceFlightCenter USA DataCenterWorkingGroupChair

2006-2019

V Michael Coleman NavalResearchLaboratory USA IGSClockProductsCoordinator

2014-2017

V Fran Boler UNAVCO USA DataCenterRepresentative

2014-2017

David Maggert UNAVCO USA NetworkCoordinator 2015-2019

EC-V,IR

Charles Meertens UNAVCO USA Appointed(IGS) 2011-2018

Sharyl Byram UnitedStatesNavalObservatory USA TroposphereWorkingGroup,Chair

2016-2019

Multi-GNSSWGandMulti-GNSSExtension(MGEX)Project

DetermineactionsnecessaryforIGStoco-optnewGNSSsystems,EuropeanUnion'sGalileosystem,China’sBeiDou,andGPSmodernization

OliverMontenbruck,Chair

Real-timeWGandReal-TimeService DemonstrateforIGSreal-timenetworkandapplicationsAxelRülke,Chair

ReferenceFrame

Globalreferenceframe,Earthorientation,stationpositionsandvelocitiesdeterminedbyGNSS

PaulRebischung,Chair

RINEX

CoordinatesthedevelopmentofGNSSobservation,navigationandmetadataformats

KenMacLeod,Chair

SpaceVehicleOrbitDynamics

Improvedunderstandingandmodelingofsatellitedynamicstowardsfurtherimprovementofpreciseorbitdetermination

MarekZiebart,Chair

TideGauge(TIGA)

Monitorlong-termsea-levelchange,attempttode-couplecrustalmotion/subsidenceatcoastalsitesfromtheirtidegaugerecords

TiloSchöne,Chair

Troposphere

EstimatewatervaporinatmospherefromtheGPSsignaldelaySharylByram,Chair

IGMAJointPerformanceMonitoring

AimedatcreatinganauthoritativeinternationalGNSSmonitoringandassessmentsystemtobenchmarktheperformanceofavailableGNSSs

TimSpringer,Chair

Figure2:IGSOrganization

OperationalActivitiesDeliveryofcorereferenceframe,orbit,clockandatmosphericproductscontinuedstrongly,withfurtherrefinementoftheReal-TimeServiceandconsiderableeffortsbeingtargetedtowardsdevelopmentofstandards.Thetransitiontomulti-GNSSalsocontinued,withadditionalGalileoandBeiDousatellitelaunchesbringingthoseconstellationsclosertooperationalstatus.

Over500IGSNetworkstationsaremaintainedandoperatedgloballybymanyinstitutionsandstationoperators,makingtrackingdataavailableatlatenciesrangingfromdailyRINEXfilestoreal-timestreamsavailableforfreepublicuse(Figure2).Thedevelopmentofamulti-GNSSsub-networkwiththegreaterIGSnetworkisledbytheMGEXproject,whichdevelopstheIGS’scapabilitytooperatewithmultipleGNSSconstellations,andhas177multi-GNSScapable(GPS+GLONASS+oneother)stations.Withinthenetwork,189IGSstationsarenowcapableofreal-timedatastreaminginsupportoftheIGSReal-TimeService.

TheCentralBureauassumesresponsibilityforday-to-daymanagement,interactionwithstation

operators,andansweringuserquestionsandrequests.ThequantityofIGStrackingdataheldon

permanentlyaccessibleserversateachofthefourglobaldatacentersincreasedatalmost2Terabytes

peryeartowhatisnowapproximately10Terabyte(over100millionfiles).Significantadditionalstorage

capabilitiesareprovidedbyregionaldatacenters.Itisestimatedthatapproximately20,000usersvisit

theIGSwebsiteandrelatedresourceseachmonth.

Figure3:IGSTrackingNetwork

Thirteenanalysiscentersand21associateanalysiscentersutilizetrackingdatafrombetween70and

350stations,fourtimesperday,togenerateandverifythequalityofhighestprecisionproducts.

Productcoordinatorscombinetheseproductsonanoperationalbasisandassurethequalityofthe

productsmadeavailabletotheusers.IGSproductuseractivitydocumentation,courtesyofCDDIS,

revealsthatin2017(January-August),anaverage106MGNSSfiles/12TBweredownloadedpermonth;

thisincludesGNSSdataandproductfiles.FocusingonIGNSproductfilesonly,thenthosetotalsare26M

GNSSproductfiles/4.5TBonaveragepermonth.ForTroposphericdownloads,CDDISreportsover46M

filestotalingover125GBin2016from500Kuniquehostseachmonth.

Alltheseactivitiesareperformedonadailybasis,year-round,withhighredundancyandreliability

basedonthepooledresourcesofmorethan200institutionsworldwide.Onlythedailycontributionsof

alargenumberofengagedindividualsmakesthissignificantundertakingpossible.

ProductQualityTheIGSAnalysisCentershavecontinuedtoimproveproductprecision,consistencyandavailability.IGS

“final”orbitsnowagreeatalevelofapproximately2cm,andfinalsatelliteclocksolutionsagreeat

approximately75psRMSwith20psstandarddeviation.ThefinalX-andY-polesolutionsagreeat

approximately0.03mas,andthefinallengthofdaysolutionsagreeatapproximately0.01μs.Products

havecontinuedtobeavailabletousers,continuouslymeetingorexceedingthespecifiedavailability

thresholds(Table3).

Table3:IGSProductQualityandAvailability

GPS Satellite Ephemerides / Satellite and Station Clocks

Sample Interval

Accuracy Latency Continuity Availability

Broadcast (for comparison)

Orbits

Daily

~100 cm

real time Continuous 99.99% Sat. Clocks

~5 ns RMS; ~2.5 ns

Sdev

Ultra-Rapid (predicted half)

Orbits

15 min

~5 cm

predicted 4x daily, at

03, 09, 15, 21 UTC

99.70%Sat. Clocks

~3 ns RMS; ~1.5 Sdev

Ultra-Rapid (observed half)

Orbits

15 min

~3 cm

3-9 hours 4x daily, at

03, 09, 15, 21 UTC

99.40%Sat. Clocks

~150 ps RMS; ~50

ps Sdev

Rapid

Orbits 15 min ~2.5 cm

17-41 hours daily, at 17

UTC 99.70%

Sat. & Stn. Clocks 5 min ~75 ps

RMS; ~25 ps Sdev

Final

Orbits 15 min ~2 cm

12-18 days weekly, every

Thursday 100%

Sat. & Stn. Clocks Sat: 30 s;

Stn.: 5 min 75 ps RMS; 20 ps Sdev

Real-time

Orbits 5-60 s ~5 cm

25 seconds Continuous 100.00%Sat. Clocks 5 s

300 ps RMS;

120 ps Sdev

Note 1: Orbit accuracies are 1D mean RMS values over the three XYZ geocentric components. IGS accuracy limits, except for predicted orbits, are based on comparisons with independent laser ranging results and discontinuities between consecutive days. The precision is better.

Note 2: The accuracy (neglecting any contributions from internal instrumental delays, which must be calibrated separately) of all clocks is expressed relative to the IGS timescale, which is linearly aligned to GPS time in one-day segments. The standard deviation (SDev) values are computed by removing a separate bias for each satellite and station clock, whereas this is not done for the RMS values.

Note 3: Availability is the percentage of time that accuracy and continuity of service meet stated specification.

GLONASS Satellite Ephemerides Sample Interval

Accuracy Latency Continuity Availability

Final 15 min ~3 cm 12-18 days weekly, every

Thursday 100%

Geocentric Coordinates of IGS Tracking Stations (over 250 Sites)

Sample Interval

Accuracy Latency Continuity Availability

PositionsofReal-timeStations

Horizontal daily

3 mm 1-2 hours daily 100%

Vertical 6 mm

Final Positions Horizontal

weekly 3 mm

11-17 days weekly, every

Wednesday 100%

Vertical 6 mm

Final Velocities Horizontal

weekly 2 mm/yr

11-17 days weekly, every

Wednesday 100%

Vertical 3 mm/yr

Earth Rotation Parameters

Ultra-Rapid (predicted half)

Polar Motion daily

integrations at 00, 06

12, 18 UTC

~200 µas

real time 4x daily, at 03, 09, 15,

21 UTC 99.70%

Polar Motion Rate

~300 µas/day

Length-of-day ~50 µs

Ultra-Rapid (observed half)

Polar Motion daily

integrations at 00, 06,

12, 18 UTC

~50 µas

3-9 hours 4x daily, at 03, 09, 15,

21 UTC 99.70%

Polar Motion Rate

~250 µas/day

Length-of-day ~10 µs

Rapid

Polar Motion daily

integrations at 12 UTC

~40 µas

17-41 hours daily at 17

UTC 100%

Polar Motion Rate

~200 µas/day

Length-of-day ~10 µs

Final

Polar Motion

daily integrations at 12 UTC

0.03 mas

~11-17 days weekly, every

Wednesday 100%

Polar Motion Rate

~150 µas/day

Length-of-day 0.01 ms

Note 1: 100 µas = 3.1 mm of equatorial rotation; 10 µs = 4.6 mm of equatorial rotation. Note 2: The IGS uses VLBI results from IERS Bulletin A to partially calibrate for LOD biases over 21-day sliding window, but residual time-correlated LOD errors remain.

Atmospheric Parameters Sample Interval

Accuracy Latency Continuity Availability

IGS Final Tropospheric

Delay: zenith path delay (ZPD) plus

north, east gradients

5 min ~4 mm for

ZPD ~ 3 weeks daily 100%

Ionosphere TEC Grid

2 hours; 5 deg (Lon.)

x 2.5 deg (Lat.)

2-8 TECU ~11 days weekly 100%

Rapid ionosphere TEC Grid

2 hours; 5 deg (Lon.)

x 2.5 deg (Lat.)

2-9 TECU <24 hours daily 100%

GovernanceTheIGShasbeenproactiveinadvancingitsorganizationandmanagement.TheIGShastakenthese

actions,amongothers,toimprovegovernanceandorganizationalperformance:

WorkingGroupchartersandmembershipAllWorkingGroupchartersandmembershiprostershavebeenreviewedforrelevancyandtoassuretheappropriatetechnicalexpertsremaininvolved.WorkingGroupsarealsonowinvitedtogiveupdatesontheirrespectiveworkshoprecommendationsatregularAssociateMemberOpenMeetings,heldatleastoncebetweenworkshops.AssociateMembershipRosterTheprocessforselectingassociatemembershasbeenreviewedandupdatedbytheIGSGoverningBoard,resultingintheformationoftheAssociateMembershipCommittee.Theconstituencyofassociatemembersisnowreviewedcontinuouslythroughouttheyearonacase-by-casebasis.PerformanceBenchmarkandRevisedStrategicPlanThroughoutmid-2016,theCentralBureauledthedevelopmentanddistributionofstrategicplanning-themedsurveystoboththeIGScommunityaswellasthebroaderIGSstakeholdercommunity.FeedbackwascollectedandanalyzedbytheCBandGBduringthestrategicplandevelopmentprocess,andusedtoshapethegoalsandobjectivesofthe2017StrategicPlan.

ExternalCoordinationTheIGScoordinatesextensivelywithmanyexternalorganizationstopromotetheIGSanddevelopkey

partnershipswithparticipantsandusers:

InternationalAssociationofGeodesy/GlobalGeodeticObservingSystem(IAG/GGOS)TheIGScoordinatesextensivelywithGGOS,includingmembershipoftheCoordinatingBoard,Consortium,SciencePanelandwithintheBureaus.AsaserviceoftheIAG,IGSalsocoordinateswiththeIAGanditsadministration.UnitedNationsOfficeforOuterSpaceAffairs(UNOOSA)InternationalCommitteeonGNSS(ICG)TheICGWorkingGroupDonReferenceFrames,TimingandApplicationsisco-chairedbytheIGSCBDirector,asistheInternationalGNSSMonitoringandAssessmentSystem(IGMAS)TaskForce.TheannualICGMeetingistypicallyattendedbyseveralIGSparticipants.SignificantprogresswasmadeinsupportingthedevelopmentofacooperativeplanwiththeICGtomonitorperformanceandinteroperabilitymetricsbetweenthedifferentGNSSs,whichisnowembodiedbyajointIGS-ICGWorkingGrouponMonitoringandAssessment.

UnitedNationsGGIMSub-CommitteeonGeodesy(formerlyGlobalGeodeticReferenceFrameWorkingGroup)AtthemostrecentsessionoftheGGIMinNewYork(August2017),theworkinggroupwasofficiallyestablishedasapermanentSub-CommitteeonGeodesy,toprovidestabilityandlong-termplanningfortheGlobalGeodeticReferenceFrame(GGRF).Previously,theCommitteeofExpertsalsoendorsedtheGGRFRoadmap,whichaddresseseachofthekeyareasofactiondescribedintheoperationalparagraphsofthe2015UNGeneralAssemblyresolution.TheseeffortsareanticipatedtoopenadditionalavenuesforinternationalcooperationfortheIGSandgeodesyingeneral.Formoreinformation,pleasevisittheUN-GGIMwebsite:http://ggim.un.org/UN_GGIM_wg1.html.InternationalEarthRotationandReferenceSystemsService(IERS)IGSandIERShavecontinuedtoextensivelycooperateintherealizationofITRF,aswellasreciprocallyparticipatingoneachother’sboards.RadioTechnicalCommissionforMaritimeServices,SubcommitteeonDifferentialGNSS(RTCM-SC104)TheIGSholdsvotingmembershiponthisinternationalstandardsorganizationforDifferentialGNSS,andchairstheRINEXWG.

InternationalFederationofSurveyors(FIG)FIGrepresentsthesinglelargestusercommunityofIGSproducts,andisalsoapotentialchannelforextendingtheIGSnetwork.IGSandFIGarecoordinatingtoreachouttousers,toconductjointworkshops,aswellastoadvocateforprecisiongeodesywithinorganizationssuchastheICG.RegionalReferenceFramesTheIGScoordinatesextensivelyatmultiplelevelswithregionalreferenceframeactivities,suchasAFREF,SIRGAS,APREF,NAREF,andEUREF.SeaLevelActivitiesThroughtheTideGaugeWorkingGroup,IGSparticipateswithintheGlobalSeaLevelObservingSystem(GLOSS)topreciselylocatetidegaugeswithintheITRF.Additionally,IGShasengagedwithmanyusercommunitiesrepresentingdifferentregionsanddisciplinesbyparticipatinginscientificworkshopsandconferenceswithpresentationsandchairingofsessions.Examplesofconferenceandworkshopsattendedinclude:InternationalCouncilofScience/WorldDataSystem(WDS),theAmericanGeophysicalUnion(AGU)andEuropeanGeosciencesUnion(EGU),theInternationalUnionofGeodesyandGeophysics(IUGG),theInternationalAssociationofGeodesy(IAG),theAsiaOceaniaGeosciencesSociety,theU.S.InstituteofNavigation,theChinaSatelliteNavigationConference,theColloquiumonScientificApplicationsofGalileo,andothers.

WorkingGroupandProjectHighlightsAdoptionoftheNewIGS14/igs14.atxFramework TheIGSadoptedanewreferenceframe,calledIGS14,on29January2017(GPSWeek1934).Atthesametime,anupdatedsetofsatelliteandgroundantennacalibrations,igs14.atx,wasimplemented.IGS14isthelatestinaseriesofGNSSreferenceframesadoptedbytheIGS.ThesereferenceframesformthebasisoftheIGSproducts,andarederivedfromeachnewversionoftheInternationalTerrestrialReferenceFrame.UpdatingtoIGS14willalignIGSproductstoITRF2014,andincreaseprecisionofthatalignmentbyintegratingadditionalavailablereferenceframestationswithmorepreciseandup-to-datecoordinates.Formoreinformation,pleasesee[IGSMAIL-7399]“UpcomingswitchtoIGS14/igs14.atx.”and“IGS14/igs14.atx:anewframeworkfortheIGSproducts.”CoincidentwiththeIGS14ReferenceFramerelease,IGSadoptedantennacalibrationupdatesinigs14.atx.Theseupdatesincluderobotcalibrationsforadditionalgroundantennatypes,increasingthe

percentageofgroundstationsintheIGSnetworkwithabsolutecalibrationstoover90%.Thiswillresultinincreasedcoordinateaccuracyforstationsequippedwiththeseantennas.SINEXandANTEXfiles,aswellasnetworkmaps,post-seismicdeformationmodels,andoffsetsareavailablefordownloadviaftpfromInstitutNationaldel’InformationGéographiqueetForestière(NationalInstituteofGeographicandForestryInformation,IGN)andÉcoleNationaledesSciencesGéographiques(NationalSchoolofGeographicSciences,ENSGReprocessingCampaigns:repro2FollowingthefirstreprocessingcampaignperformedbytheIGSin2008,asecondreprocessingcampaign(repro2)wasfinalizedin2015.NinedifferentACsreanalyzedthehistoryofGNSSdatacollectedbyaglobaltrackingnetworkbackto1994usingthelatestavailablemodelsandmethodology.BesidessupplyinganimprovedconsistentsetofGNSSgeodeticproducts,onemajorgoaloftherepro2campaignwastoprovidetheIGSinputtothelatestreleaseoftheInternationalTerrestrialReferenceFrame(ITRF2014).TheindividualACproductswerecombinedintoofficialIGSrepro2productscalled"ig2".Resultsfromtherepro2terrestrialframecombinationsaredescribedinRebischungetal.(2016;https://doi.org/10.1007/s00190-016-0897-6),whileresultsfromtherepro2orbitandclockcombinationsaresummarizedinIGSMAIL-7411(https://igscb.jpl.nasa.gov/pipermail/igsmail/2017/008601.html).Troposphererepro2resultsarecurrentlybeingprocessedandevaluated.Multi-GNSSGlobalExperiment(MGEX)Inthebeginningof2016,thestatusoftheMulti-GNSSExperiment(MGEX)oftheIGSwaschangedtoaPilotProjectbytheIGSGoverningBoard.In2016,thenumberofIGSmulti-GNSSstationsincreasedfromalmost130toabout180,seeFigure1.Abouthalfofthestationsalsoprovidereal-timestreams,mainlyviathededicatedMGEXcaster(http://mgex.igs-ip.net/)butalsoviatheIGS-IPcaster(http://igs-ip.net).BothcastersareoperatedbyBKGandprovidethereal-timestreamsindifferentversionsoftheRTCM-3MSMformat.Sixanalysiscenters(ACs)contributeorbitandclockproductstoMGEX:CNES,CODE,GFZ,JAXA,TUM,andWuhanUniversity.MGEXincludesthenewGPSsignals,newRussianGLONASSsignals,theJapaneseQZSS,theChineseBeiDou,andtheEuropeanUnion’sGalileo.

Real-TimeServiceTheIGS-RTSisbasedonaglobalnetworkofIGSstationsprovidingdatastreamstotheRTSobservationbroadcasters.ThereareseveralobservationbroadcastersinoperationincludingthefirstlevelglobalcastersatBKG,CDDISandIGSCentralBureau.ThereareeightrealtimeAnalysisCentres(AC)whichusedifferentsoftwarepackagestocomputeepoch-wiseorbitandclockproducts.ThelargenumberofACsensuresahighredundancyoftheserviceontheonehandandastrongqualitycontrol

Thankstothecontributionsfromalargenumberofpartners,theIGSRTSoperatesadensehighquality

realtimeGNSSnetwork.TheobservationdataisusedtoderiveorbitandclockproductswhichallowuserPPPatdecimeteraccuracy.Alimitationistheconvergencetimeofabout30minutesandthelatencyofthecombinedproductsof20-30s.TheIGSRTSensuresopenaccesstoitsdataandproductsandsupportsopenstandardsanddataformats.DataandproductsareprovidedviaTCP/IPconnections.Therangeofapplicationsisfocusedonscientificandeducationaltopics,suchaspositioning,navigationandtiming,Earthobservationsandresearch;andotherapplicationsthatbenefitthescientificcommunityandsociety.

InfrastructureImprovements<<Nachohaspromisedtoprovideanupdate>>TheInfrastructureCommittee(IC)hasfocusedonimprovingtheIGSnetwork,aswellasplanningthechangeoveroftheIGSinfrastructuretosupportMulti-GNSSandreal-timeefforts,whilemaintainingintegrityofcoreproducts.TheIChasledeffortstorevisetheIGSsiteguidelinestopromoteproperpracticeinoperatingGNSSstations.Themostrecentrevisionin2012addednewproceduresforupgradingstationequipmentdesignedtominimizedisruptiontotheIGSreferenceframe,aswelloperatingstandardsforstationsparticipatingwithintheReal-timeService.TheIChasalsoledanexperimenttoassesstheeffectsof21IGSstationsthatareco-locatedwithSLRorVLBIsiteswhereradomeshavenotbeencalibratedtoIGSstandards.Thiswillaidinmappinganydiscontinuitiesthatmayariseasequipmentisupgradedatthesestations.Analysisiscurrentlyinprogressforanumberoftheparticipatingstations.DataCenterCoordinationDuringthereportingperiod,theIGSDataCenterWorkingGroup(DCWG)workedwiththeInfrastructureCommittee(IC)tointegratemulti-GNSSdatainRINEXVersion3formatintotheoperationaldirectorystructureattheGlobalDataCentersinordertopromotetheuseofmulti-GNSSdataandthenewRINEXformat.TheWGalsocoordinatedasitemetadataactivityformanagingtheinformationcontainedinIGSsitelogsandtopromotetheuseoftheGeodesyMLapplicationschemaformanagingGNSSsitemetadataingeneral.ReceiverIndependentExchangeFormat(RINEX)TheRINEXWorkingGrouphasassumedleadershipinmaintenanceandfurtherdevelopmentoftheRINEXdataexchangestandard,incooperationwithRTCM-SC104,andhasledtherecentreleaseofRINEX3.03.TheRINEXWorkingGrouphasworkedincooperationwiththeICtoprepareaplantotransitionfromRINEX2.xtoRINEX3.x.Additionally,theRWGhasencouragedandsupportedthedevelopmentofopensoftwaretoolsforRINEX3.xdatahandlingandqualitycontrol.TideGaugeBenchmarkMonitoringTheTideGaugeBenchmarkMonitoringWorkingGroup(TIGA)oftheIGScontinuesitssupportforclimateandsealevelrelatedstudiesandorganizationsconcernedherewith(e.g.,GGOS,OSTST,UNESCO/IOC).TheTIGAWGprovidesverticalgeocentricpositions,verticalmotionanddisplacementsof

GNSSstationsatornearaglobalnetworkoftidegaugesandworkstowardsestablishinglocalgeodetictiesbetweentheGNSSstationsandtidegauges

TIGANetworkoperatorworkswithTideGaugeandGNSSstationoperatorstomakeexistingstationsavailabletoTIGA,amain(ongoing)taskistoupdatethecurrentdatabaseofexistinglocaltiesbetweenGNSSandtidegaugebenchmarks.Bytheendof2016about173localtiesinformationweremadeavailableathttp://www.sonel.org/-Stability-of-the-datums.html?lang=en.ThenumberstationsdirectlycommittedtoTIGAthenumberoftieshasrisento76,with820GNSS@TGstations(with119stationsweredecommissioned).TheTIGA-WGcarriedforwardtheGLOSS-Task“PrioritiesforinstallationofcontinuousGlobalNavigationSatelliteSystem(GNSS)neartotidegauges.ReporttoGlobalSeaLevelObservingSystem(GLOSS)”byKing,M.A.(2014)forthedensificationandextensionoftheTIGAObservingNetworktoGGOS.TheresponsebytheGGOSCoordinatingBoardwasreceivedearly2017.ImprovedSatelliteForceModels <noresponsefromMarekregardingupdate.Pleaseadviseifthefollowingshouldbemodified,orifthissubtopicshouldbedeletedfromthistravaux>>TheSatelliteOrbitandDynamicsWorkingGrouphasdevelopedimprovedsatelliteradiationpressuremodels,whichareavailabletoIGSthroughtheUniversityCollegeLondonwebsite.ThesemodelsareexpectedtoimprovethequalityoftheIGSorbitproductsonceimplementedbytheIGSanalysiscenters.BiasandCalibrationResearchTheBiasandCalibrationWorkingGroupcontinuescoordinatingresearchactivitiesrelatedtobiasretrieval,analysis,andmonitoring.Presently,thegroupisconsideringC1W–C1C,C2W–C2C,andC1W–C2Wdifferentialcodebiases(DCB).Potentialquarter-cyclebiasesbetweendifferentphaseobservables(specificallybetweenGPSL2WandL2C)areanotherissuetobedealtwith.InthefaceofGPSandGLONASSmodernizationprogramsandupcomingGNSS,suchastheEuropeanGalileoandtheChineseBeiDou,carefultreatmentofmeasurementbiasesinlegacyandnewsignalsbecomesmoreandmorecrucialforcombinedanalysisofmultipleGNSS.In2016and2017,aGNSSbiasreprocessing(forGPS/GLONASS)usingtherecentlyimplementedobservable-specificsignalbias(OSB)parameterizationwascarriedoutatCODEfor1994-2016RINEXdata.Theoutcomesofthisreprocessingeffortaredailynormal-equation(NEQ)filesforGPSandGLONASScodebiasparametersthatareconformtobothglobalionosphereandclockanalysis.

Thecombinationofthesedailybiasresultsintoacoherentlong-term(1994-present)GPS/GLONASSbiasproductisanotherkeyachievement.Suchabiasproductisparticularlyusefulforapplicationswherecalibrationintheabsolutesensearecrucial(e.g.,forGPStiming,oratomicclockcomparisons).Additionally,CODE’sclassicGPSDCBproductandthemostresentGNSSbiasresultsaremadeavailableusingtheBias-SINEXFormatVersion1.00.TroposphereProductThegoaloftheIGSTroposphereWorkingGroupistoimprovetheaccuracyandusabilityofGNSS-derivedtroposphereestimates.Itdoesthisbycoordinating(a)workinggroupprojectsand(b)technicalsessionsattheIGSAnalysisWorkshops.TheWorkingGroupiscurrentlyfocusingon:automatingcomparisonsoftroposphereestimatesobtainedusingdifferentmeasurementoranalysistechniques,standardizationofthetropo_sinexformat,andautomatedAnalysisCenterEstimateComparisons.

Dr.ChristineHackmanchairedtheIGSTWGthroughDecember2015.Dr.SharylByramhaschaireditsincethenandalsooverseesproductionoftheIGSFTEs.IGSFTEsareproducedwithintheUSNOEarthOrientationDepartmentGPSAnalysisDivision,whichalsohoststheUSNOIGSAnalysisCenter.TheUnitedStatesNavalObservatoryproducesIGSFinalTroposphereEstimatesfornearlyallofthestationsoftheIGSnetwork.Each24-hrsiteresultfileprovidesfive-minute-spacedestimatesoftotaltropospherezenithpathdelay(ZPD),north,andeastgradientcomponents,withthegradientcomponentsusedtocompensatefortroposphericasymmetry.

Dailyzenithpathdelayestimatesarebeinggeneratedwithanapproximatethree-weeklatencyforallactiveIGSsites,basedonPrecisePointPositioningtechniques.IGSFinalTroposphereestimatesareusedbyscientistsworldwidetosupportclimate-changeandmeteorologicalstudies,and46.3millionestimatesfilesfromover1000distincthostsweredownloadedin2012alone.IonosphereProductFollowingtheIGSWorkshop2014inPasadena,ionosphericfluctuationmapproductswereestablishedasapilotprojectoftheIGSservice.Thecurrentproductrosterincludes:finalGIM(pleasenotethatGIMsalsoincludeGPSandGLONASSstations’andsatellites’DCBs);rapidGIM;predictedGIMfor1and2daysahead(pilotproduct).Recentkeyaccomplishmentsinclude:

• IGSGlobalionospherepredictedproductsfor1and2daysahead(pilotproduct).ThisnewIGSproductsarecurrentlybasedonpredictedionospheremapspreparedbyUPCandESA.

• IGSGlobalionospheremapswith1hourtimeresolution.ThisnewIGSproductsarecurrentlybasedonionospheremapspreparedbyUPC,ESAandCODE.

• IGSGlobalIonosphereMaps(GIMs)nowincludedifferentialcodebiases(DCBs)forGLONASSsatellites.

• ThepilotphaseofthenewIGSionosphericproduct-TECfluctuationsmaps

MoreInformationForgreaterdetailabouttheaforementionedactivities,efforts,andcomponents,pleaserefertotheIGSTechnicalReports,availablefordownloadontheIGSKnowledgeBase.