Present Status of the SCAR GPS Epoch Campaigns

Reinhard Dietrich

Institut für Planetare Geodäsie, TU Dresden

1 Introduction

The SCAR GPS Epoch Campaigns are a part of the working program of the SCAR Working Group on Geodesy and Geographic Information (WG-GGI), and belong to the main program Geodetic Infrastructure in Antarctica (GIANT), chaired by J. Manning, Australia.

The main goals of the SCAR GPS Epoch Campaigns are:

· establishment and maintenance of a precise geodetic reference network in Antarctica, linked to the International Terrestrial Reference Frame (ITRF);

· utilization of the Antarctic geodetic network for geodynamic research;

· linking Antarctic tide gauges to the ITRF;

· providing reference for other GPS applications in Antarctica

The status report presented here gives an overview of activities since 1995, including the field campaigns and the data analysis.

2 Field campaigns

The GPS campaigns take place every year from 20 January, 0:00 UT until 10 February, 24:00UT. The main observation standards were:

• provide daily data sets of 24 hours starting at 0:00 UT
• use only dual frequency geodetic GPS receivers
• data sampling interval 15 seconds (if possible)

Special attention should be paid to stable mounting of the GPS markers. The campaign data were completed by the data of the permanent tracking sites of the International GPS Service (IGS) at the southern hemisphere.

3 Database

All data and station documentation sheets were collected and filed at the Institut für Planetare Geodäsie (Technische Universität Dresden) in Germany. An overview with the participating stations, as they exist in the data base, is shown in Table 1. The data are available for all participants (see also http://www.tu-dresden.de/ipg/SCARGPS/database.html).

4 Data analysis

The data analysis carried out several research groups with different software packages (see Table2). The groups provided individual solutions, which were intercompared and finally combined (Dietrich et al. 1996, 1998 and 1999).

The final coordinates are summarized in Tables 3, 4 and 5.

5 Future work

The SCAR GPS Epoch Campaigns will be continued. The next campaign will be the SCAR GPS 2000 Campaign ("The Millenium Campaign") carried out in the well-tried schedule.

(see also http://www.tudresden.de/ipg/SCARGPS/...database-html).

6 Acknowledgements

Thanks are directed to all individuals and agencies, who supported the field projects, and in particular to the SCAR Working Group on Geographic Information, which acted as a scientific focus.

References

Dietrich R., R. Dach, G. Engelhardt, B. Heck, H. Kutterer, K. Lindner, M. Mayer, F. Menge, H.W. Mikolaiski, W. Niemeier, M.Pohl, H. Salbach, H.W. Schenke, T. Schöne, G. Seeber und G. Soltau 1996: The SCAR 95 GPS Campaign: Objectives, Data Analysis and Final Solution. In R. Dietrich (ed.): The Geodetic Antarctic Project GAP95 - German Contributions to the SCAR 95 Epoch Campaign. Deutsche Geodätische Kommission, Reihe B, Heft 304.

Dietrich R., R. Dach, J. Perlt, H.W. Schenke, T. Schöne, M. Pohl, G. Soltau, G. Engelhardt, H.W. Mikolaiski, G. Seeber, F. Menge, W. Niemeier, H. Salbach, K. Lindner, H. Kutterer, M.Mayer 1998: The SCAR GPS Campaigns: accurate geodetic reference in Antarctica. In: Forsberg, R., Feissel, M., Dietrich, R. (eds.): Geodesy on the Move, Gravity, Geoid, Geodynamics, and Antarctica. Proc. of the IAG Scientific Assembly, Rio de Janeiro, Sept. 39, 1997, Springer Series: IAG Symposia, Vol. 119, Springer Heidelberg, 1998.

Dietrich R., R. Dach, G. Engelhardt, J. Ihde, W. Korth, H.J. Kutterer, K. Lindner, M. Mayer, F.Menge, H. Miller, C. Müller, W. Niemeier, J. Perlt, M. Pohl, H. Salbach, H.W. Schenke, T.Schöne, G. Seeber, A. Veit and C. Völksen 1999: ITRF coordinates and plate velocities from repeated GPS Campaigns in Antarctica an analysis based on different individual solutions. Journal of Geodesy, Springer (in review).

Table 1: List of stations (except IGS stations in Antarctica)

Table 2: Analysis groups and software packages

Table 3: Coordinate solution of GPS Campaign 1995. ITRF94, Epoch 1995.1

Table 4: Coordinate solution of GPS Campaign 1996. ITRF94, Epoch 1996.1

Table 5: Coordinate solution of GPS Campaign 1998. ITRF96, Epoch 1998.1

Multi-Disciplinary GPS Support in Antarctica

Bjorn Johns

University NAVSTAR Consortium - UNAVCO. www.unavco.ucar.edu

UNAVCO is funded by the U.S. National Science Foundation to provide GPS equipment, technical support, and data archiving services to Antarctic scientists participating in (or collaborating with) the United States Antarctic Program. Over 20 projects per year are supported, and represent various scientific disciplines including geology, geophysics, glaciology, biology, volcanology, and atmospheric sciences. GPS precision requirements range from sub-centimeter to meter level. Applications include crustal deformation, ice sheet dynamics, surveying, mapping, and vehicle and instrument positioning. Static, continuous, rapid static, kinematic, and real-time RTK and DGPS techniques are used to support these diverse GPS applications. From supporting these efforts, UNAVCO offers significant resources to the Antarctic GPS community, including a substantial geodetic GPS equipment pool, support infrastructure, and Internet based documentation.

Support Provided

GPS equipment and technical support (including training and data processing) are available year-round. During the austral summer, project support is provided from a UNAVCO "satellite" facility at

McMurdo Station. An engineer is available to provide training and technical support, and manage the equipment pool of over 20 dual frequency geodetic GPS receivers, RTK and DGPS equipment, data processing software, and ancillary equipment.

McMurdo Differential GPS System

In 1997 UNAVCO installed a differential GPS broadcasting system as infrastructure at McMurdo Station. The system broadcasts standard RTCM SC-104 version 2.1 corrections, providing centimeter level RTK corrections in the vicinity of McMurdo Station and meter level DGPS corrections throughout McMurdo Sound. A repeater provides DGPS coverage in Taylor Valley, the most visited of the Dry Valleys. The differential corrections are broadcast continuously during the summer, and as requested during the winter. System information, available equipment, specifications, and operational documentation are available in the McMurdo DGPS Station section of the UNAVCO web page (Figure 1).

Figure 1. McMurdo Differential GPS Station

Figure 2. Web Geodetic Data Index

interchange (DIF) format (Figure 4). Information is also provided for GPS Continuous Stations, with direct links to available information about U.S. NSF sponsored sites, and a link to the SCAR maintained index of international sites.

Other GPS Resources

Many other GPS activities supported by UNAVCO also provide relevant information and resources to Antarctic GPS users as well as the broader GPS community. The UNAVCO facility has supported the installation of over 150 continuously operating GPS stations worldwide and currently monitors the operation of 194 stations. These include stations from the NASA Global GPS Network and various NASA and NSF funded regional networks. From supporting these efforts, UNAVCO offers experience in remote, autonomous GPS site design and support to the GPS science community. Areas of design and field experience include year-round solar powered autonomous

Research applications of this system include mapping/GIS work, locating diving and other research sites on the McMurdo Sound sea ice, and positioning scientific sample and instrument locations in McMurdo Sound and Taylor Valley. The system also provides a valuable asset for McMurdo Station operational applications, including the annual ice runway layout, construction surveying, and search and rescue vehicle navigation.

Internet Based Data and Meta-Data Archiving

All GPS data handled by UNAVCO are archived, both locally at McMurdo Station and at the UNAVCO Facility archive after the field season. The Geodetic Data section of the UNAVCO Polar Program web page (Figure 2) is the central access point for data from UNAVCO supported Antarctica GPS projects. Graphical access to geodetic benchmark data, project meta-data, and continuous stations has recently been added.

Project GPS data are stored in the UNAVCO data archives, ensuring data safeguarding and future accessibility. Data from Geodetic Benchmarks (Figure 3) collected to geodetic standards are archived by site name, and precise site coordinates and site descriptions are readily available. As this database of precise GPS coordinates continues to grow, future projects benefit by having pre-established geodetic control in their field study areas. Project Meta-Data from UNAVCO supported GPS projects are archived both graphically by project location and by field season, following the SCAR, NSF, and NASA data

Figure 3. Benchmark Example

Figure 4. Meta-Data Example

The SCAR Geodetic Infrastructure of Antarctica

John Manning

Australian Surveying and Land Information Group, P0 Box 2, Belconnen,
Canberra, ACT 2617, Australia

Background

The scientific exploration of Antarctica has been the composite result of many nations research, not just the activities of a single individual nation. Contemporary scientific research in Antarctica began in earnest during the second International Geophysical Year in 1957/58. At that time the Scientific Committee for Antarctic Research (SCAR) was formed to coordinate and promote cooperation in scientific research through discipline based scientific working groups. In 1958 SCAR established a working group on Geodesy and Cartography to promote a joint approach to the positioning and mapping needs of Antarctic field scientists.

Geodetic Survey

Traditionally the positioning of geographic features on the Antarctic continent and measurement of baseline distances to neighbouring southern continental land masses was only achievable from astronomical observations or local trigonometric surveys on exposed rock. But with the advent of artificial geodetic satellites it was possible to begin to apply space geodesy techniques to the problem of linking the isolated geodetic surveys together and the measurement of intercontinental baselines.

SCAR Working Group on Geodesy and Geographic Information

The Scientific Committee for Antarctic Research (SCAR) was formed at the Hague in March 1958 to coordinate the scientific research of nations active in Antarctic during the third International Geophysical Year (IGY) 1957-58. The SCAR objective was to coordinate cooperative Antarctic scientific research and a series of specialist working Groups were established to meet this objective. It was soon realised that scientific researchers needed maps and positions to assist them in their field activity and to document their work in a largely unknown continent. Six months later the SCAR Working Group on Geodesy and Cartography was created to facilitate this work. In 1988, the name was changed to the Working Group on Geodesy and Geographic Information (WG -GGI) to better reflect its total scope of activities.

The early Geodesy objectives of the WG-GGI were to provide a control base for exploration and mapping using celestial techniques or limited area survey triangulations. It was not possible to measure accurate baseline between continents or to connect widely separated local triangulations with the technology available at the time.

With advent of artificial geodetic satellites these connections became possible using space Geodesy techniques. The first Antarctic space geodesy programs were the initiatives of individual countries as part of more extensive global programs, and no coordinated international geodetic program yet 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 nations geodetic networks with view to a joint approach, but due to logistic limitations no overall plan was implemented.

The positional accuracies achievable from the developing geodetic techniques are summarised in Table 1.

The SCAR GPS Campaigns

Despite the early GPS work by Counselman (1981) producing promising potential for accurate geodetic survey, it was not until the late 1980's that GPS emerged as a geodetic tool with a potential for Antarctic. The XX meeting of SCAR in Hobart 1988 endorsed a proposal by Australia to test the developing GPS technique for mapping control and Geodesy applications in monitoring crustal motion.

Table 1. Approximate accuracies on Antarctic baselines

SCAR 1990 GPS Campaign

Australia arranged the initial GPS geodetic quality field observations in Antarctica, drawing on non-geodetic applications for ice surface motion the previous year (Allison 1989). The data gathered in the January 1990 campaign consisted of data from five different receiver types. It included data from the Cooperative International GPS network (CIGNET) program which was observing in the Southern Hemisphere at the same time. This resulted in a network of stations in Antarctica, Australia, and New Zealand (Table 2).

Initial computation was carried out using the Berne precision software to produce the first intercontinental GPS baseline measurements from Antarctica. (Govind et al 1990). The results showed acquisitions problems with the design of the equipment and difficulty was encountered with ionospheric instability from the high level of solar sunspot activity. However 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

SCAR 1991 GPS Campaign

The second phase of the pilot study was undertaken the following summer in January 1991, and was synchronised

Table 2. GPS observational sites 1989/90

with the first seven days of the first GPS IERS and Geodynamics Experiment 1991 (GIG 91) global campaign. Data from the sites listed below were processed using the GAMIT software and the results indicated that precisions of the order of 1 part in one hundred million were achievable (Morgan and Tiesler 1991): Mawson; Dovers; Georg Von Neumayer (ice station); O'Higgins; Terra Nova Bay; McMurdo.

SCAR 1992 GPS Campaign

A major observational SCAR GPS campaign was implemented in January 1992. Its objective was to produce definitive baselines between rock sites in Antarctica and intercontinental ties between Gondwanaland continental

Table 3. GPS observational sites 1992 field campaign

fragments. The project involved twelve nations in the observation of twenty-eight stations in three phases for sites located in Antarctica and on the surrounding southern continents and islands shown in Table 3. The campaign was successful and processed in GAMIT at the University of Canberra.SCAR 1993 and 1994 GPS Campaigns

SCAR 1993 and 1994 GPS Campaigns

Despite their success, the GPS campaigns were logistically costly and it was difficult to arrange occupation of all sites at the same time with differing nations 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: Mcmurdo; Mawson; Amundsen-Scott (ice station); Casey; Davis; Macquarie Island.

This was a significant technological advance as it provided a potential continuous time series of observations and a network of key sites to used as a control framework for temporary occupations at different times. In 1994 permanent GPS trackers were also installed at: O'Higgins; Syowa; Kerguelen.

SCAR 1995 GPS Campaigns

In 1995 Germany took over coordination responsibility from Australia for the summer epoch campaigns beginning with the GAP95 survey, principally focused on the geodynamics of the Antarctic Peninsula (Fig.1).

Results of the GAP95 campaign are published in Dietrich (1996). Germany has continued to coordinate the ongoing summer epoch campaigns. The sites occupied in each phase are summarised in Table 4.

Table 4. GPS sites occupied in SCAR Epoch campaigns 1995-1999

Figure 1. GAP95 Observational Sites

The Geodetic Infrastructure of Antarctica (GIANT) Program
At the XXII SCAR meeting in 1992, a proposal for a Geodetic infrastructure of Antarctica (GIANT) program was endorsed. The objective was to establish a precise network of points on rock sites across Antarctica, connected by space geodesy techniques which would enable existing all data on local geodetic datums to be directly related to produce a common geographical spatial data infrastructure. This was collectively identified as the Geodetic Infrastructure for Antarctica (GIANT) program.

GIANT program objectives:

The GIANT program objectives are to:

· Provide a common geographic reference system for all Antarctic scientists and operators.

· Contribute to global geodesy for the study of the physical processes of the earth and the maintenanceof the precise terrestrial reference frame
· Provide information for monitoring the horizontal and vertical motion of the Antarctic.

This geodetic infrastructure will enable earth science investigators involved in individual disciplines (such as geodynamics, oceanography, geophysics, glaciology and geodesy.) to monitor temporal changes in horizontal and vertical positions, including sea level, relative to a fixed geocentric reference system traceable over a period of decades. The geodetic network will provide the spatial framework for use by scientists based on rock sites and as a reference platform for moving ice cap studies.

Implementation and development of the GIANT program has continued since 1992 and there are now seven key elements in the GIANT Program. These elements are summarised below for the current period 1998 to 2000.

1. Permanent Geodetic Observatories

Project Leaders: John Manning, Australia, Hans Werner Schenke, Germany

Goal: To develop an infrastructure of permanent geodetic stations to bring all individual geodetic networks to a common datum, and to provide geodetic information for the global monitoring of natural earth processes.

Key activities:
· Collaborate with other SCAR scientists to identify requirements for space geodetic sites In conjunction with SCAR working groups design an extended network of continuous geodetic observatories;

· for manned stations

· for remote locations

· Support continuation of O'Higgins VLBI for scientific purposes and as an important contribution to the global reference frame

· Establish priorities for on-line satellite data retrieval from ground stations

· Deliver regular space geodesy solutions to IGS and IERS

· Post details of all permanent sites on web site

· Develop and publish GPS base station specifications

· Evaluate accurate local ties between collocated techniques

· Facilitate tide gauge data to Southern Ocean Sea Level Centre

2. GPS Epoch Campaigns

Project Leaders: Reinhard Dietrich, Germany, Andres Zakrajsek, Argentina, Kevin Dixon, UK, Michel Le Pape, France, E Dongchen, China, Hector Rovera, Uruguay, Alessandro Capra

Goal: To densify the geodetic infrastructure established from the permanent observatories. This will includes links to individual geodetic networks, tide gauges and the computation of surface movement vectors within a common Antarctic reference frame.

Key activities:
· Establish guidelines for ground mark monuments

· Co-ordinate annual epoch campaigns

· Arrange orderly data archive and data access from these campaigns

· Undertake GPS connections to Tide gauge benchmarks

· Deliver results to ITRF in conjunction with results from permanent observatories

· Notify results of each campaigns occupations

3. Physical Geodesy

Project Leaders: Alessandro Capra, Italy, Lars Sjoberg, Sweden, Andres Zakrajsek Argentina, Hans Werner Schenke, Germany, John Manning, Australia.

Goal: Collection and analysis of physical geodesy data, for the development of a new high resolution Geoid for the Antarctic.

Key activities:
· The collation of extensive data holdings related to topography, bathymetry and gravity as essential inputs to Geoid computation, includes:

· Data collection and analysis of gravity related data ground/airborne/satellite data.

· Collect relevant data from satellite altimetry

· Collaboration with International Geoid Service (IGES) and International association of Geodesy (IAG)

· Collaboration with SCAR WGs Solid Earth Geophysics, Geology, Glaciology

· Collaboration with BEDMAP, ADGRAV, RAMP as data for Geoid computation

· Participate in the ADMAP meeting and Earth Science in Antarctic, NZ, in 1999

· Preparing data base of information from collated information prior to computation

· Evaluation of EGM96 improvement over OSU91 in Antarctica

· Facilitate computation of improved tidal models

· Prepare for computation of high resolution Geoid model

4. GLONASS Evaluation

Project Leaders: John Manning, Australia, Larry Hothem, USA)

Goal: Evaluate the benefit of GLONASS for global geodesy, Antarctic geodesy and navigation applications in Antarctica.

Key activities:
· Participate in the International GLONASS Experiment (IGES) pilot project with dual frequency GLONASS instruments at IGS collocated sites

· Retrieve data by satellite for analysis

· Analyse GLONASS orbits, reference frame differences and ground positions for geodesy and navigation applications in Antarctica

· Participate in presentation of IGEX results 1999

· Report on use of GLONASS for Antarctic Geodesy and navigation.

5. Differential GPS Base Stations

Project Leaders: Larry Hothem, USA, Hans Werner Schenke, Germany, IHO, Kevin Dixon, UK, Jan Cisak, Poland, Alessandro Capra, Italy.

Goal: To increase the utility of Geodetic GPS base stations by making DGPS corrections available for radio transmission for scientific field and operational use.

Key activities:
· Identify global standards for use in marine DGPS transmission using Geodetic base stations

· Develop options for base station sites for shipping navigation coverage of Antarctic Peninsula.

· Examine DGPS for real time kinematics and aviation applications in Antarctica and combination with geodetic accuracy base stations

· Liaison with COMNAP regarding transmission of GPS corrections at base stations.

6. Remote Geodetic Observatories

Project Leaders: (Larry Hothem, USA, Alessandro Capra, Italy, John Manning, Australia)

Goal: To deploy GPS equipment at unattended remote Antarctic localities for regional densification of geodetic infrastructure, and for scientific studies of surface geodynamics. This requires remote power input and data retrieval. This technology is not quite available at present and needs further development.

Key activities:

· Monitor and report on use of solar, wind and other methods of power generation for data logging information at remote GPS sites

· Monitor developments for remote retrieval of GPS data from remote sites by satellite communication techniques

· Collaboration with non-SCAR researchers

7. Information Access

Project Leaders: John Manning, Australia, All members of GIANT program

Goal: To publicise and distribute results of GIANT activities to the general Antarctic community.

Key activities:

· Prepare general papers on GIANT activities for publication.

· Ensure ready access to data from permanent observatories from host databases

· Establish cross links from WG-GGI web site to individual geodetic sites

· Develop DIFs for geodetic data in conjunction with JCADM

· Establish newsletter/newsgroup communication for information distribution on Web

· Monitor web posting of photo identifications on web sites

· Continue interaction with representatives on SCAR working Groups

· Develop IAG Commission X sub Commission on Antarctic Geodetic networks

· Publish WGS84-ITRF information paper and circulate within SCAR (SCAR Bulletin)

· Arrange an Antarctic Geodesy Symposium (AGS99) in Europe at the time of IUGG

Current Activities of the GIANT Program

The activities of the GIANT Program are reviewed every two years by the Working Group during the SCAR meetings. An interperiod symposium or business meting is also usually held. Work has coninued in alldefined elements since the SCAR meeting in Concepion in July1998. The WG-GGI website (www.scar-ggi.org.au/geodesy/giant.htm) has been populated with details of the current status of Antarctic Geodetic observatories illustrating:

· Permanent GPS installations
· Permanent Tide Gauge installations
· Absolute gravity fundamental sites
· DORIS sites
· VLBI sites

These are shown below as extracts from the WG-GGI web site(Figs 2&endash;6).

Figure 2. Permanent GPS installations

Figure 4. Absolute gravity sites

Figure 5. DORIS sites

Figure 6. VLBI sites

Permanent sites

Antarctica is important in a global geodesy sense. Global Geodesy 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 geodetic observatories provide data to rectify this imbalance with some continuous GPS sites using satellite data retrieval systems to make their data available to the IGS database. Data is available from other sites only by annual manual downloads. The status of the permanent observatories is shown in Figure 2 as extracted from the WG-GGI web site

Epoch campaigns

Germany coordinated the GPS Epoch campaigns for the past five years of summer epoch camapigns 1995 to 1999. The objective has been to densify the ITRF reference frame points beyond the fiducial network of permanent GPS stations. Details of the 1995 campaign are given in Dietrich et al (1997) and the sites occupied that time are shown in Figure2 above. The complete list to sites occupied during the five year period is summarised in Table 4 . Dat is available through Dr Dietrich at University of Dresden (Dietrich@ipg.geo.tu-dresden.de)

Geoids

An accurate definition of the geoid is severely constrained in Antarctica by the lack of gravity information, especially across the inland of the continent. . Australia produced early versions of the Antarctic Geoid based on GEM and OSU gravity data sets, which are available on the AUSLIG web site http://www.auslig.gov.au/geodesy/antarc/antgeoid.htm. The current situation with the geoid in Antarctica remains hampered by the continuing lack of ground gravity data. A grid of geoidal separation values initially from the OSU91A geopotential model and subsequently from the recent EGM96 that can be used to interpolate a separation value for any location south of 60 degrees latitude are available on the AUSLIG webs site for individual interpolation

These enable GPS users to refer their observed elevations (ellipsoidal values) to a nominal sea level surface, although the values are limited by the amount of data used in the Antarctic region

The gathering of geophysical data to improve the Antarctic Geoid is a major undertaking. Data collection is being undertaken cooperatively with other groups through the newly formed SCAR Neo Antarctic Group of Specialists (ANTEC) and the BEDMAP, ADGRAV and RAMP projects.

GLONASS

GLONASS observations undertaken in collocation with GPS at McMurdo in January /February 1999. Results seminar will be held as part of ION 99 conference in Nashville in September. Report on Antarctic applications will be prepared following this seminar.

DGPS applications

The current DGPS standard for base stations used by the United States Coastguard base stations is the specification recommended for use in the GIANT Program. Details are available on the web site (www.navcen.uscg.mil/dgps/dgeninfo/dgpsant.htm). The WG-GGI has investigated the establishment of DGPS transmission base stations along the Antarctic Peninsula . With three sites distributed as below then DGPS accuracies of better than two metre would be made available to all shipping along the Eastern side of the Peninsula a significant safety measure. The recommended sites are : King George Island; Palmer; San Martin or Rothera.

This would also produce a significant benefit for aviation in the region and could be used by scientists for field work with hand held receivers. Eventually this DGPS transmission network would be extended through liaison with COMNAP to other manned stations around the continent during shipping or aviation activities.

The current DGPS standard for base stations used by the United States Coastguard base stations is the specification recommended for use in the GIANT Program. Details are available on the web site (www.navcen.uscg.mil/dgps/dgeninfo/dgpsant.htm).

Remotely operating GPS sites

At present there is a technological limitation on operating and maintaining remote placed continuous GPS equipment to be self powered and able to transmit data back to manned bases or directly by satellite to global data centres. Technological developments are continuing and ANTEC has arranged a special seminar at Pasadena USA in August to discuss the state of the technology for remote power and data transmissions for remote sites.

Antarctic research symposia

There have been a number of recent Antarctic Geodesy events held including:

· AGU San Francisco December 1998

· EUG10 Strasbourg March 1999

· EGS 99 The Hague April 1999

There will be an Antarctic Symposium arranged in conjunction with ANTEC during the European Geophysical Symposium in Italy in April2000 and a splinter GIANT meeting may be held at that time to incorporate Scandinavian and Russian geodesists.

Group of Specialists on Antarctic Neotectonics (ANTEC)

At the SCAR XXV meeting in Concepcion, Chile, Prof. Dalziel, IUGS Delegate, presented to Delegates a joint recommendation from the Working Groups on Geology, on Solid-Earth Geophysics, and on Geodesy and Geographic Information, that SCAR should establish a new Group of Specialists on Antarctic Neotectonics (ANTEC). The presentation highlighted some unique aspects of the Antarctic continent such as:

· It lies at the centre of a lithospheric plate that, unlike any other, is almost entirely surrounded by spreading ridges and, furthermore, has been essentially in a polar position for the last 100 million years;

· It appears to lack the intra-plate seismicity that characterises all other continents;

· It includes at least one intra-plate rift system, stretching from the Ross Sea to the Weddell Sea, that has unique characteristics including possible implications for the stability of the West Antarctic Ice Sheet.; and

· It is covered by the only extant continent-scale ice sheet, which applies unusual stresses to the crust.

The presentation emphasised the current development of new technologies that are making possible new studies in geodynamics and neotectonics. These provide an opportunity for earth scientists and allow Antarctica to be placed more precisely in the global framework. (SCAR Bulletin 133, April 1999). The WG-GGI has strong representation in ANTEC as shown in Table 5.

Collocation with other geodetic techniques

GPS is a major technique in use in Antarctica but for global observations collocation with other techniques is important such as DORIS, Absolute Gravity, Tide Gauges, and VLBI

The first Antarctic VLBI experiment was observed at Syowa in 1991 (Kurihara et al 1991) using a temporary configuration. A permanent installation was established by Germany at the Chilean base of O'Higgins in 1993 and has participated in a number of southern hemisphere campaigns. (Bosworth 1993), (Seeger 19994). Japan refurbished the antenna at Syowa as a permanent installation in 1998 and experiments between other sites in Australia and South Africa are continuing, whilst O'Higgins continues to be operated during the summer months.

Absolute gravity sites have been established in Antarctica by Finland, Italy, Japan, and by the USA in the McMurdo region. A super conducting Gravimeter has been in operation for four years at Syowa.

Permanent recording tide gauges have been deployed at a number of sites including Mawson, Syowa, Cape Roberts, Davis and Casey and O'Higgins.

DORIS beacons are operational at Syowa, Kerguelen, Rothera and Dumont Durville. To date Satellite Laser Ranging has not been undertaken in Antarctica, but there are plans to incorporate it in the future.

Conclusion

The GIANT program can make a significant contribution to the work of earth scientists in Antarctica such as in the ANTEC program. GPS and other precise geodetic observations have been made over a number of years and already provide a reference framework for geodynamics. These current movement velocities are available at a number of for comparison with long term geophysical records. An extended network of GPS sites is being developed in conjunction with ANTEC for occupation when the technology permits to contribute contemporary velocities to give a better understanding of the crustal motion both within Antarctica and in relation to the southern hemisphere land masses.

The geodetic infrastructure also provides the base linkages to consolidate individual geodetic networks into a single geodetic datum so that all spatial data dependent on geodetic positions can readily be integrated into an Antarctic Spatial Data base

References

Allison, I.(1989) NCPM Glaciology Program 1988/89; Dynamics of the Lambert Glacier Outlet System. Unpublished Report, Australian Antarctic Division, Hobart. Anderle, R.J. (1977) Stations in the TRANET Network. In Part] National Geodetic Satellite Program (NASA SP365), pp 203-207, National Aeronautics and Space Administration, Washington D.C.

Counselman, C.C., and Gourevitch, S.A. (1981) Miniature interferometric terminals for Earth surveying ambiguity and multipath with Global Positioning System. IEEE Transactions on Geoscience and Remote Sensing Vol GE-]9 No 4, October 1981

Dietrich, R. (1996) The Geodetic Antarctic Project GAP95 &endash; German Contributions to the SCAR 95 Epoch Campaign, Deutsche Geodätische Kommission, Müchen, Germany

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 the Syowa Station in Antarctica and its Future Plans. paper presented to the Chapman Conference on Geodetic VLB I; 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., 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.

Reece, J. and Brownd, J.(1977) Station Coordinates in GEM 5 and GEM 6. In Part 1 NationalGeodetic Satellite Program (NASA SP 365), pp 380-381, National Aeronautics and Space Administration, Washington

Scientific Committee for Antarctic Research, (1998) SCAR Bulletin, No. 133, April 1999, Scott Polar Research Institute, Cambridge, UK.

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