TAMDEF-I Project (TransAntarctic Mountains Deformation Monitoring Network) L. Hothem (1) and M. Willis (1,2) (1) U.S. Geological Survey (2) Byrd Polar Research Center, Ohio State University Antarctic Geodesy Symposium, AGS01, Saint Petersburg, Russia, July 2001

19 July 20012

3 South Victoria Land TransAntarctic Mountains DEFormation Monitoring (TAMDEF-I) project

19 July In November 1996, the Byrd Polar Research Center/Ohio State University, jointly with the US Geological Survey, began work on establishing a network of about 30 stations located at sites in the South Victoria Land region of the Transantarctic Mountains. The 4 th and last in series of GPS observing campaigns for this phase of the studies was completed in the December 1999-January 2000 field season. High quality data were obtained in each of the 4 observing campaigns. Objective: test predictions of leading models for ice sheet change and tectonism

19 July Transantarctic Mountains Deformation Monitoring Project (TAMDEF) South Victoria Land Cooperative project - Ohio State University and USGS Three GPS observing campaigns completed – , 97-98, 98-99, and field seasons Objective: test predictions of leading models for ice sheet change and tectonism Other geodetic measurements: –International GPS Service (IGS) stations in and near Antarctica –Absolute gravity –Tide gages

19 July Transantarctic Mountains Deformation Monitoring Project (TAMDEF) South Victoria Land TAMDEF-I -- Four GPS Observing Campaigns –1-year intervals –Field seasons: , 97-98, 98-99, and Measure rock motion - 3-dimensional –Expected signals are: 1. Glacial rebound 2. Tectonic 3. Volcanic –Directions and patterns of these motions mostly distinct –GPS measurements designed to discriminate among them –Test predictions of leading models for ice sheet change and tectonism Long-term project –TAMDEF-II is p lanned

19 July GPS surveys formed geometrical elements generally at three spatial scales Long baselines (100 to 400 km) that span the features most expected to show motion. Simultaneous tracking time is at least 2 days, often 7 days. –Station at Cape Roberts (ROB0) occupied continuously during each of the 4 observing campaigns. –Some other stations with continuous data sets spanning periods of up to 15 days. Short baselines (10 to 25 km) crossing suspected fault zones. Simultaneous tracking time 2 to 24 hours. Very short baselines (0.05 to 0.20 km) at each site (footprint array) to test for local motion due to such processes as frost action. Simultaneous tracking time is generally 60 minutes.

19 July 20018

BTL ARR ROB TAMDEF Station Absolute Gravity Station Other GPS Reference Stations Local fault surveys MCM4 ERR

19 July To obtain high accuracy or mm-level GPS measurements where biases are adequately modeled or minimized and which are free of blunders due to human error, requires careful planning and successful execution of the field methodologies employed.

19 July (1) Special pins set in rock outcrop (2) Established a set of reference points, footprint array, at each site to monitor stability of the primary monument (3) Used specially designed fixed-height level mounts to ensure at a high confidence level, sub-mm repeatability for the relationship of antenna reference point (ARP) to the monument reference point (4) Employed late model GPS receivers with Dorne Margolin model choke ring antennas (5) Collected multiple-day 24-hour data sets simultaneously at 8 to 12 stations Field Procedures

19 July Threaded stainless steel 20-cm rod glued into hole drilled in bedrock TAMDEF Monuments Nylon cap to protect threads Plastic marker stamped with 4-character station name

19 July

19 July Attaching and leveling the antenna mount

19 July Special Fixed-Height Level Mount for TAMDEF Monuments Station ARR0 located adjacent to IGS station MCM4. At each station of the TAMDEF network, relationship of Antenna Reference Point (ARP) to station mark (bottom of divot for stainless steel pin) is repeatable for each setup at the sub-mm level. ARP

19 July Arrival Heights (ARR) TAMDEF Network IGS Station MCM4 TAMDEF Station ARR0

19 July IGS Station - MCM4 McMurdo Station - Operational since January 1994 MCM4 ARR0 MCM4 with raydome cover

19 July GPS Equipment Ashtech Z12 Trimble SSE and SSi Receiver Models Antenna Models Ashtech & Trimble Dorne Margolin Choke Rings

Footprint Array for ARR

19 July Cape Roberts (ROB)

Footprint Array for ROB ROB0

19 July Station ROB0

19 July Cape Roberts Tide Station (Installed 1991) co-located with TAMDEF Station ROB0 (Established November 1996) Install permanent GPS/GLONASS observing station during field season

19 July Bettle Peak (BTL) Footprint array

19 July TAMDEF Station ERE Mount Erebus, Antarctica

19 July Reliable Power Supply Essential for Continuous Data Collection Transport Case and Site storage for GPS receiver and two 40 amp-hour gel-cell batteries 30-watt solar panel generating system

19 July Details on Field Procedures Sites selected with relatively clear horizon –No obstructions above 10 –Minimal obstructions above 5 Mask angle for data collection = 5 Data collection sampling rate: –Daily (24-hour) data sets = 30-sec or 15-sec –Footprint surveys = 5-sec Data management –All raw data translated into RINEX format –Categorized by station location and day of operation –Compressed and stored on CD-ROMs Documentation for site and each occupation –Description of geology at each site –Satellite sky view –Model and serial numbers of GPS equipment used –Duration of site occupation

19 July Quality Analysis & Data Processing Data quality analysis –TEQC Toolkit by UNAVCO 24-hour data sets –Precise point positions computed by use of JPL/NASAs automated GIPSY-OASIS II package –Differential positions computed by use of National Geodetic Survey/NOAAs PAGES package –All processed using IGS orbital coordinate data Footprint array surveys –Software packages used include GPSurvey V2.3 Ashtech GPPS Magellan AOS

19 July SUMMARY Methodology employed for TAMDEF GPS observing campaigns was successful overall in meeting goals for: –data free of errors due to blunders –minimizing multipath effects –multiple-day data sets relatively free of gaps