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SCAR Report 23

The Evolution of the GIANT Program

John Manning Geoscience Australia
John.manning@ga.gov.au

1. Historical Background

GIANT is the acronym for the Geodetic Infrastructure of Antarctica program of the Scientific Committee for Antarctic Research (SCAR). SCAR was formed at The Hague in February 1958. It evolved from a Special Committee on Antarctic Research which was established by the International Council for Science (ICSU) to co-ordinate the scientific research of the twelve nations who were active in Antarctica during the International Geophysical Year in 1957-58. The ongoing objective of SCAR is to promote scientific collaboration in Antarctic research.

At the first SCAR meeting in 1958 Cartography, as it was known then, was part of Working Group 2 (along with Geology, Glaciology and Morphology). At the III SCAR meeting in September 1959 Cartography met as a Working Group in its own right. The following year at IV SCAR in September 1960, a Permanent Working Group on Cartography was established . The Chief Officer was General Laclavére from France. The name was subsequently changed at V SCAR in October 1961 to the Working Group on Geodesy and Cartography. The Working Groups Chief Officer was B P (Bruce) Lambert from Australia. Since then the Chief Officer position has been held by Australian representatives from the National Mapping Division. In 1988, at XX SCAR in Hobart, the name of the group was changed to the Working Group on Geodesy and Geographic Information (WG -GGI) to better reflect its total scope of activity.

From its inception the working group encouraged compatible mapping of the Antarctic continent and established a set of recommendations and standing resolutions as mapping standards. Initially it recommended the use of the Hayford 1924 International spheroid as the basis for mapping and geodetic computations. The essential role of Geodesy within the working group at that time was the provision of control for exploration and mapping. This has since evolved to include the monitoring of the current tectonic motion of the continent and its linkage to other continents.

Since the formation of the WG-GGI at V SCAR in 1961 group meetings were usually held at the time of the SCAR meetings and all activities were the responsibility of the Chief Officer. At the XX SCAR meeting in Hobart in 1988 the modus operandi was changed from this single responsibility in producing a growing number of products, with a greatly increased work load. A more distributed arrangement was identified, which was reinforced at a special meeting hosted by Germany in Frankfurt in June 1990 as an alternate venue to the SCAR meeting that year. At the subsequent XXII SCAR meeting at Bariloche in 1992, Drew Clarke from Australia was elected Chief Officer and the operational aspects of the WG-GGI was completely reviewed changing from a focus on mapping standards and individual national activities, to a theme based structure with distributed project responsibilities. The Geodetic Infrastructure of Antarctic program was identified as GIANT at the meeting. Since that time the overall WG-GGI program has further evolved into two major umbrella streams each with an overall coordinator:

This structural grouping proved successful and both streams initiated projects and produced products which were increasingly became available through the web site as Internet technology developed.

Table 1 List of SCAR Antarctic Geodesy Symposia

The concept of a business meeting at the time of the SCAR week working of working group meetings directly before the main SCAR meeting, and a specialist interperiod meeting was developed. This commenced with the USGS hosting a workshop in Flagstaff immediately before the Boulder IUGG meeting in 1995. This approach was further developed when Chile proposed and hosted a specialist Antarctic Geodesy Symposium (AGS) in Santiago immediately before the Concepion XXV SCAR. There have now been four AGS symposia as in Table 1 above culminating in this fifth AGS03 event in Lviv Ukraine. This series of meetings has provided an important continuity of face to face contact whilst focussing on program milestone for individual projects in the GIANT program.


Figure 1: Structure of the Geoscience Standing Group (GSSG)

At the XXVI SCAR meeting in Shanghai in 2002 the long standing and successful WG-GGI (including GIANT) was merged with other SCAR working groups to form the Geoscience Scientific Standing Science Group (GSSG) and as such lost its direct reporting stream to the SCAR Executive Committee. The WG-GGI was renamed the Geospatial Information Group of Experts (GIG) with the intention to broaden its scope to also include Geophysical network information. In the new structure GIANT continues as the coordinating program for SCAR Antarctic Geodesy but as a sub program within GIG, which in turn is a sub group of GSSG. GIANT continues also to contribute expertise and resources to the SCAR Antarctic Neotectonics (ANTEC) program. It is cross linked with the International Association of Geodesy regional sub commission on Antarctica as the GIANT convener is also the co chair of the IAG sub commission on Antarctic Geodetic networks.

2. Technical Background : The progression to space geodesy

Until the 1960s the positioning of geographic features on the Antarctic continent and measurement of baselines to other continental land masses was still only achievable by local triangulation surveys within Antarctica and astronomical astronomic observations. Triangulation chains were difficult to establish due to the need for multi station visibility for angle observations. The networks which were established were limited to the immediate vicinity of the base stations, or as small local area triangulations in isolated mountain areas. It was impossible to connect these local triangulations.

Optical and microwave electronic distance measuring (EDM) techniques were introduced to the Antarctic continent in the mid sixties, which enabled trilaterations, and large traversing loops, rather than pure triangulation to be undertaken, producing expanded but still isolated geodetic networks. This remained unchanged until the advent of man made satellites, although several over snow survey traverse connections between mountain features were carried out using EDM techniques.

With the advent of man made satellites, space geodesy was applied to address the problem of intra continental connection and to accurately determine the coordinates of some Antarctic stations in a global reference frame. In 1969 the global astro-triangulation PAGEOS program occupied Antarctic sites at McMurdo, Mawson, Palmer and Casey, photographing passive satellites against a star background. In the 1970s active microwave positioning from satellites proved more useable than the PAGEOS optical photographic approach and firstly Transit Doppler and later GPS became available on global scale. The improvement in positional accuracies achievable from the different geodetic techniques is summarised in Table 1 below.

Table 1: Positional accuracy progression in Antarctica sites

The early Antarctic space geodesy programs were the initiatives of individual countries as part of more extensive global programs, and no coordinated international geodetic program existed on the Antarctic continent. In 1976 the SCAR WG-GGI began to look at the possibility of linking the individual national geodetic networks by Doppler techniques and work commenced on gathering the extent of each nation’s geodetic networks with view to a joint approach, but due to logistic limitations no overall plan was implemented to link the individual networks.
In the late 1980's the application of the GPS military navigation system emerged as a civilian geodetic tool with a potential for Antarctica. The XXth meeting in 1988 endorsed a proposal by Australia to test the developing GPS technique for mapping control and potential applications in monitoring crustal motion. This pilot study was undertaken in two phases:

Table 2: GPS observational sites 1990

Despite problems encountered the trial clearly showed that baseline accuracies in the order of one metre over intercontinental distances were possible even with the low number of GPS satellite available at the time (Govind at al 1990).

With the success of these feasibility studies the WG-GGI initiated an ongoing series of summer GPS epoch surveys. These were coordinated by Reinhard Dietrich from Germany (Dietrich 1996), (Dietrich, 2001) and the sites occupied are shown in Figure 4. All epoch data is archived at University of Dresden as an ongoing collection for science research (Dietrich@ipg.geo.tu-dresden.de).

Despite their success, the GPS campaigns were logistically costly and it was difficult to arrange the simultaneous occupation of all sites, being subject to different logistic arrangements. Consequently in 1993 permanent GPS sites were installed to provide fundamental fiducial stations to link epoch surveys together. The permanent stations were:

This was a significant technological advance as it provided a potential continuous time series of observations and a network of key sites which could be used as a control framework for subsequent occupations at different times. In 1994 permanent GPS trackers were also installed at :

Since that time permanent GPS trackers contributing continuous data to world data bases on a daily basis have been established at SANAE (1999) and Palmer. Other annual download GPS base stations are operating at Terra Nova bay, Maitri, Dumont Durville, Cape Roberts, Belgrano and Zhong Shan.(see figure 5)

The technology to power GPS equipment at unattended remote Antarctic observatory sites during the sunless winter is under current development with varying degrees of success. Ideally this requires remote power and satellite data retrieval strategies. The Australian National University has deployed 4 stations in the vicinity of the Prince Charles Mountains in East Antarctica and continues development for regular satellite downloads from some of those sites. Japan is trialling a remote site on an island some 30 km from Syowa and USGS is trialling annual download from remote sites at Finger Point, Mt Fleming and Cape Roberts (collocated with a remote operating tide gauge). This remote operation technology is not quite proven and needs further development to be ready for the international polar year in 2007.

3. The Geodetic Infrastructure of Antarctica

At the XXII SCAR in 1992 the results of the SCAR GPS Antarctic Project 1990-92 were assessed and it was decided to extend the GPS projects to develop collocation network of other techniques such as VLBI, Absolute Gravity, DORIS and tide gauges. This was collectively identified as the Geodetic Infrastructure for Antarctica (GIANT) the coordinating program for Geodesy.
The ongoing GIANT program objectives are to:

Since 1992 the GIANT program has been revised and endorsed at each major SCAR conference on a two yearly basis. The components of the current program are:

3.1 Geodesy program (GIANT)below as:

1. Permanent Geoscientific Observatories
Project Leader: Australia - Mr John Manning
Goal: To develop an infrastructure of permanent geoscientific (ie. seismologic, geomagnetic, geodetic and gravimetric) stations to bring all individual networks to a common datum, and to provide geoscientific information for the global monitoring and analysis of natural earth processes

2. Epoch Crustal Movement Campaigns
Project Leader: Germany - Prof Reinhard Dietrich
Members: Italy, Chile, Japan, China, Australia, USA
Goals:
1. To densify the geodetic infrastructure established from the permanent observatories; and
2. To develop a deformation model for surface movement vectors within a common Antarctic reference frame.

3. Physical Geodesy
Project Leader: Italy - Prof Alessandro Capra
Members: Germany, Australia, Russia, USA, Japan, Canada
Goal: Compilation and analysis of physical geodesy data, for the development of a new high resolution Geoid for the Antarctic.

4. Geodetic Control Data Base
Project Leader: Australia - Mr Glenn Johnstone
Members: Germany, UK, USA
Goal: Maintain the master index for Antarctic positional control, including all levels of accuracy

5. Tide Gauge Data
Project Leader: Japan - Dr Kazuo Shibuya
Members: Australia, China, Germany, New Zealand, Italy, Russia, USA (Amos), UK (Woodworth), other specialists as required
Goal: To consolidate the collection of and access to Antarctic tide gauge information

6. Atmospheric Impact on GPS Observations in Antarctica
Project Leader: Poland - Dr Jan Cisak
Members: Germany, Italy, USA, Australia (IPS), Norway, China, IGS
Goal: To understand the iononspheric and tropospheric impact of the atmosphere on the quality of GPS observations in Antarctica

7. Remote Observatory Technologies
Project Leader: USA - Mr Larry Hothem
Members: Japan (GSI), Australia, Italy, Netherlands (Swartz)
Goal: Identify technology and monitor developments for the deployment of geophysical and geodetic measurement sensors, and ancillary support equipment, at unattended remote (no existing infrastructure for power, shelter and communications) Antarctic localities.

8. Ground Truthing for Satellite Missions
Project Leader: Germany - Prof Reinhard Dietrich
Members: Italy, Australia, USA (U of Texas)
Goal: To ensure new satellite missions are integrated with the Antarctic geodetic system

9. Geodetic Advice on positioning limits of special areas in Antarctica
Project Leader: Chile - Tnt Col Rodrigo Barriga
Members: Germany, Australia, USA
Goal: To provide advice to SCAR, through the Geoscience Standing Scientific Group on the geodetic aspects of protected area definitions.One of the complex elements in The GIANT program is the development of the ellipsoid to geoid separation values to obtain heights above sea level from GPS or altimeter observations. An accurate determination of the Antarctic geoid continues to be severely hampered by the scarcity of gravity information, especially the interior of the continent. Australia produced early versions of the Antarctic Geoid based on GEM and OSU gravity data sets, which are available on the web site. In 1996 NIMA produced EGM96, a new global Gravity data model which however still suffers from lack of Antarctic gravity data. A grid of geoidal separation values based on EGM96 is available NIMA web site and which can be used to on line interpolate a separation value for any location (http://www.nima.mil/GandG/egm96/intpt.htm)

Whilst these earth gravity models still are inadequate for extensive Antarctic research, long wave gravity models from the CHAMP and GRACE satellite are beginning to become available and will improve the situation. Medium wave length gravity however is also required and this can be produced from airborne gravity. The experience from the successful aero gravity activities of Denmark and the Unites States of America in Greenland and the Artic Ocean offer a technique to dramatically improve this aspect of the Antarctic gravity data set and provide the base for the subsequent computation of the geoid within the GIANT Geoid project. Ultimately terrestrial gravity will be integrated by introduction of precise Absolute gravity at origin sites top produce a continental wide gravimetric framework
GIANT also provides important geodesy input to two other major activities:

3.2 The Antarctic Neotectonics Group of Specialists ANTEC.

This group of specialists was established following the SCAR XXV meeting in Concepcion with three GIANT representatives. The ANTEC objectives are intertwined with the need for a precise geodetic framework over Antarctica in the establishment of remotely operated sites away from the manned coastal stations and the integration with other geodetic techniques.

3.3 The International Terrestrial Reference Frame (ITRF)

Antarctica is important in the context of global geodesy. In the past global models have heavily relied on observations from Northern Hemisphere sites and the results do not always fit in the Southern Hemisphere or represent the best global picture. Antarctic space geodetic observatories have provided data to rectify this imbalance. Some continuous GPS sites make their data available to the International GPS Service (IGS) using satellite data retrieval systems. Data from continuous GPS sites in Antarctica were used in ITRF 2000 primary determinations (Altimimi 2001) and the epoch surveys have also been processed by Dietrich (2001) as densification of the global reference frame. This results in a network of official published IERS coordinates (with velocities) for Antarctic rock sites which can be used by any scientists in the Global reference frame. Through the GIANT program SCAR has accepted the recommendation that all geodetic networks in Antarctic should be computed in the ITFR 2000 reference fame using The GRS80 ellipsoid.

4. Conclusions

There has been considerable international cooperation in Antarctic Geodesy since SCAR was formed in 1958. The GIANT program was identified in the SCAR 1992 meeting and has evolved as the coordinating program for all SCAR Antarctic geodesy. With advent of man made satellites Geodesy has advance significantly linking isolated geodetic networks and monitoring tectonic motion.

A number of permanent GPS receivers have been installed in Antarctica and data is increasingly being retrieved by satellite transmission from these sites. This fiducial network of GPS points, augmented by VLBI and other techniques, forms the basis for an integrated geodetic infrastructure as the basis for all scientific spatial data. Data from these sites in Antarctica are of ongoing importance to global geodesy, especially in the determinations of precise orbits and the integration of different observational techniques. These sites provide a stable platform for combining summer epoch campaigns, densifying the ITRF network across Antarctica.

The application of space geodesy technology now enables a more comprehensive study of crustal movements within Antarctica and its relationship to other fragments of the ancient Gondwanaland. GIANT is making a significant contribution to the work of other Antarctic earth scientists such as the newly formed ANTEC group of specialists which is concerned with developing a better understanding of the crustal dynamics of Antarctica.
To meet the continual advancing requirement for accuracy for studying Antarctic geodynamics stresses, GIANT will expand the geodetic network to provide a very stable Antarctic reference frame for geodynamics and become involved in aerogravity campaigns to supplement satellite gravity data in order to improve the geoid.

5. References

Dietrich, R.(1996) ‘The geodetic Antarctic Project GAP95 –German Contributions to the SCAR 95 Epoch
Campaign’, Deutsche Geodatische Kommision, Munchen, Germany 1996

Dietrich, R. (2001) ‘Present Status of the SCAR GPS Epoch Campaigns Report of the Second SCAR
Antarctic Geodesy Symposium, Polish Academy of Sciences, Warsaw 14-16 July 1999 in SCAR Report (20) May , Scientific Committee on Antarctic Research, Cambridge

Govind, R., Morrison, T., and Manning. J. (1990) 'Antarctic GPS Pilot Project - A Status Report.' Paper presented to SCAR Working Group Symposium, IFAG Frankfurt, June 1990.

Kurihara, N.,Kondo, T.,, Takahashi Y.Takahashi F., and Ejiri, M.(1991) 'The Results of the test VLBI experiments with Syowa Station in Antarctica and its future plans.' paper presented to the Chapman conference on Geodetic VLBI; Monitoring Global Change. Washington DC.

Lambert, B.P. (1975)' Geodetic Surveying in Antarctica 1970-1974; Report to the International Association of Geodesy. SCAR Working Group on Geodesy and Cartography. Canberra

Manning, J., (1999) ‘The SCAR Geodetic Infrastructure of Antarctica’ Report of the Second SCAR
Antarctic Geodesy Symposium, Polish Academy of Sciences, Warsaw 14-16 July 1999 in SCAR
Report (20) May , Scientific Committee on Antarctic Research, Cambridge

Manning, J., and Morgan, P. (1992) 'Antarctica - Where is it, and where is it going.' The Australian Surveyor vol 37 (1) pp 5-12, March 1992

Manning, J., Morrison, T. and Murphy, B. (1990)'The Transition to GPS: Australian Experience in
Antarctica with Satellite Positioning.' Proceedings X1X FIG International Congress, Commission
5 pp 296-311, FIG, Helsinki.

Morgan, P., and Tiesler, R. (1991) First Epoch Baselines between Antarctica and Australia - January 1990.' Australian Journal of Geodesy, Photogrammetry and Surveying, December 1991


Figure 2 Tide Gauge Installations

Figure 3 Absolute gravity sites

Figure 4. GAP1995 Observational Sites


Figure 5 Continuous GPS sites