1. Task AR-07-03: Global Geodetic Reference Frames Report to ADC-5 prepared by Hans-Peter Plag (IAG/GGOS) Nevada Bureau of Mines and Geology and Seismological Laboratory University of Nevada, Reno, Nevada, USA

2. Recalling: Task AR-07-03: Global Geodetic Reference Frames “Ensure the availability of accurate, consistent, homogeneous, long- term stable, global geodetic reference frames as a mandatory framework and the metrological basis for Earth observation.” Goals: User requirement coordination: Establish a comprehensive GEOSS database of user requirements concerning georeferencing and geodetic reference frames by identifying, describing and establishing links to relevant user communities in the nine societal benefit areas and conducting appropriate surveys. Georeferencing: Ensure the availability of appropriate global geodetic reference frames for GEOSS. Task proposed by International Association of Geodesy (IAG)/Global Geodetic Observing System (GGOS)

3. Task Progress and Status: POC: IAG/GGOS (Hans-Peter Plag) Lead organization: IAG/GGOS Current contributions: - Germany - CEOS - IAG/GGOS - Korea - Italy - U.K. ? - ISPRS ? Additional contributions: - Through GGOS 2020: more than 40 Experts (including IGOS-P, GLOSS, GOOS, GCOS) Deliverables in 2007: GGOS 2020 Reports GGOS 2007 Workshop Task AR-07-03 is on the list of Early Achievements to be included in the Report to the EOS in November 2007

4. Deliverable 1: GGOS 2020: The Global Geodetic Observing System: Meeting the Requirements of a Global Society on a Changing Planet in 2020 Output: Two documents: - Strategy document: short document for politicians, decision makers, funding agencies - Reference document: long, comprehensive document with all the user requirements and details of GGOS in 2020 mainly for those actually doing the work GG S 2020

5. Activities in 2007: Retreat and GGOS 2020 Writing Team Meeting in February 2007, ~40 Participants Several GGOS Steering Committee Meetings Version 0.17 of the Reference Document released on May 29 th for internal review in IAG and Task Team More than 300 individual comments received Status: Reviewing of comments and editing of document to be finished before September 30 th GG S 2020

6. Relevance: Reference frames and positioning important for nearly all SBAs; Geodetic observations (Earth's shape/kinematic, gravity field, and rotation) relevant for at least Disaster, Water, Climate, Weather; Reference frames and observations highly relevant for research; Crucial for many processes in a modern society; Reference frames indispensable for exploring the planets and the solar system. GG S 2020

7. Main User Requirements: celestial reference frame: accurate to 25 µ as, stable to 3 µ as/year terrestrial reference frame: accurate to 1 mm, stable to 0.1 mm/year including geocenter, scale accurate to 0.1 ppb, stable to 0.01 ppb/year. Earth orientation parameters: accurate to 1 mm with a latency of 2 weeks, 3 mm in near real-time. static geoid: accurate to 1 mm, stable to 0.1 mm/year, with a spatial resolution of 10 km. time varying geoid: accurate to 1 mm, stable to 0.1 mm/year, with a spatial resolution of 50 km and temporal resolution of 10 days. GG S 2020

8. Main Recommendations: Terrestrial reference frame: transition from research to operational in order to underpin Spatial Data Infrastructure; Identification, deployment (where necessary), and maintenance of an operational global core network; Development of a global water cycle service; Operational gravity-satellite missions; GNSS seismology for early warning; Consistency across the three fields (Earth's shape/kinematic, gravity field, rotation); Participation in GEO, contribution to GEOSS Steps towards intergovernmental frame work (reference frame, core infrastructure) GG S 2020

9. Further Processes and Schedule for the GGOS 2020 documents: Goal: Prepare GGOS 2020 documents for distribution to GEO Members and Participating Organizations Proposed Schedule: - October 2007: Review of Reference Document by ADC - Potential editing early in November - Distribution of Document to GEO Members mid November GG S 2020

10. Deliverable 2:

11. Workshop is part of the International Geohazards Week Workshop is outreach activity to space agencies and geohazards community Workshop is a GEO/GGOS workshop Preparations are well advanced and in good shape

12. Future Task Activities: Discussion of GGOS 2020 Recommendations with GEO Members and Participating Organizations Development of intergovernmental frame work GGOS Stakeholder Conference (potentially in March 2008 in Italy, near Bologna) User Requirements Database