IGS Real Time Pilot Project: Analysis Centre Activities

ESOC Navigation Support OfficeIGS Workshop 2008

Miami

IGS Real Time Pilot Project: Analysis Centre Activities

Loukis Agrotis4 June 2008


Miami Outline

Objectives Schedule Analysis Centre Status RT Processing Issues and

Challenges Conclusions


Miami ObjectivesGeneration and Dissemination of a

Real Time Combination Product– Accurate (clocks < 0.5 ns, predicted orbits <5 cm )– With low latency ( <? )

»5-10 sec from observation time should be achievable

– High Availability»Low Downtime»Available to a potentially large user set

– High Reliability»But with no “service guarantees”

– These are for commercial providers to offer


Miami ScheduleApril 08: AC teleconferences and formal PP kick-off June 08: Clock RINEX and SP3 Products from 3 ACs

Start routine comparisons Develop and validate tools for combination solution Prototype process on ESOC FTP server (to be eventually

transitioned to CDDIS)

July 08: Start Disseminating ComparisonsSept 08: Batch Combination ProductJan 09: RT Product Dissemination by ACs

All ACs OperationalMarch 09: RT Combination Product Available


Miami Analysis Centre Status

Centre StatusRT Product Availability

ESOC

RT Clocks and TZD and NRT Orbits from batch process. Real Time products currently streamed internally. Real Time product dissemination outside ESOC once agreement on formats and protocols for the PP is reached.

Immediate

NRCanRT Clocks and TZD and NRT Orbits from batch process. Currently distributing RT products via satellite.

Immediate

BKG with TU Prague

RT clocks as double difference clock corrections, using IGS ultra-rapid orbits. RT products and Broadcast ephemeris orbit corrections are disseminated via NTRIP.

Immediate

IGGRT Clocks based on IGU orbits. Currently generates online comparisons with IGU clocks.IGU orbit residuals in near future

Immediate


Miami Analysis Centre Status

Centre StatusRT Product Availability

GMVSP3 and clock RINEX files every hour (with current capabilities). RT system under development.

January 2009 (TBC)

University of Newcastle

RT obits and clocks. Clocks determined with smoothed pseudo ranges.

January 2009

KASI

Real Time data processing with estimation of orbits, clocks, ionospheric and Tropospheric products.AC for global ionospheric products from RT-IGS stations.

January 2009 (TBC)

TU Catalonia AC for RT Ionospheric Products. June 2009

Chalmers

Emphasis is on a Tropospheric product for weather forecasting. Intend to participate as a RT Analysis Centre using own software for estimation of orbits and clocks.

January 2009 (TBC)

Geo++ Analysis contributions using best efforts. January 2009


Miami Issues and ChallengesProduct and Data Formats

Formats for RT products– Formats still to be defined and agreed– Main issue that could hold back progress of RT PP

Formats for Data– Predominant data formats are RTCM, RT-IGS / SOC and BINEX for GPS– Main challenge for data formats is support for generic GNSS (GLONASS,

Galileo, Compass) and higher accuracies– Discussions now taking place on future requirements thanks to the good

efforts of NRCan and BKG– Objective is to find the best fit among currently proposed format revisions

and to influence their evolution so that our requirements are met.

Transport Protocols– NTRIP via HTTP, TCP or UDP– UDPRelay – Either or both could be used to disseminate the RT Combination Product


Miami Issues and ChallengesNetworkIssues

Excellent results are possible thanks to the contributions of a number of agencies

Large area with no network coverage results in network fragmentation. Example from 22 April shows circled stations and satellites which experienced jumps in our solution.

Densification of the network is being actively pursued


Miami Issues and ChallengesNetwork Issues

The clock correction plots show that all clocks in the South-East have jumped by the same amount, while the remaining clocks were unaffected

Several similar occurrences of this phenomenon have been observed


Miami Issues and ChallengesFilter Tuning Issues

Jump experienced in PRN19 at start of new pass with CAS1

CAS1 clock appears to reset with each new pass

Changes needed to the tuning of the filter so that the CAS1 clock behaviour is better modelled


Miami Conclusions

RT PP is now active, thanks to the enthusiasm and support of the participating groups, particularly NRCan and BKG.

Success of the AC activity relies on the generation of high quality RT products but also on making the correct decisions on formats and protocols to ensure a wide distribution

Densification of the network in areas of low coverage is a priority

An IGS RT service will complement and increase the usefulness of the various commercial offerings for this type of service - it should not be viewed as competition to any of the current offerings of potential participants.

Documents

IGS Real Time Pilot Project: Analysis Centre Activities