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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, AGS’01, Saint Petersburg, Russia, 18-20 July 2001
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South Victoria Land
TransAntarctic Mountains DEFormation
Monitoring (TAMDEF-I) project
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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 4th 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
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Transantarctic Mountains Deformation
Monitoring Project (TAMDEF)
South Victoria Land
• Cooperative project - Ohio State University
and USGS
• Three GPS observing campaigns completed
– 1996-97, 97-98, 98-99, and 99-00 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
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Transantarctic Mountains Deformation
Monitoring Project (TAMDEF)
South Victoria Land
• TAMDEF-I -- Four GPS Observing Campaigns
– 1-year intervals
– Field seasons: 1996-97, 97-98, 98-99, and 99-2000
• 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
–
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TAMDEF-II is planned
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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.
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BTL
MCM4
ERR
ARR
ROB
TAMDEF
Station
Local fault surveys
Other GPS Reference Stations
Absolute
Gravity Station
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.
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Field Procedures
(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
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TAMDEF Monuments
Nylon cap to
protect threads
Plastic marker stamped
with 4-character station name
Threaded stainless steel 20-cm rod
glued into hole drilled in bedrock
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Attaching and leveling the antenna mount
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Special “Fixed-Height” Level Mount for
TAMDEF Monuments
ARP
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.
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Station ARR0 located
adjacent to IGS station
MCM4.
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Arrival Heights (ARR)
TAMDEF Network
IGS
Station
MCM4
TAMDEF
Station
ARR0
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IGS Station - “MCM4”
McMurdo Station - Operational since January 1994
MCM4 with
raydome cover
MCM4
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ARR0
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GPS Equipment
Receiver Models
Ashtech Z12
Trimble SSE and SSi
Antenna Models
Ashtech & Trimble Dorne
Margolin Choke Rings
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Footprint Array for ARR
Cape Roberts (ROB)
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Footprint Array for ROB
ROB0
Station ROB0
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Cape Roberts
Tide Station
(Installed 1991)
co-located with
TAMDEF Station
ROB0
(Established
November 1996)
Install permanent
GPS/GLONASS
observing station
during 2000-2001
field season
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Bettle Peak (BTL)
Footprint array
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TAMDEF Station “ERE”
Mount Erebus, Antarctica
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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
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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
–
–
–
–
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Description of geology at each site
Satellite sky view
Model and serial numbers of GPS equipment used
Duration of site occupation
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Quality Analysis & Data Processing
• Data quality analysis
– TEQC Toolkit by UNAVCO
• 24-hour data sets
– “Precise point positions” computed by use of JPL/NASA’s
automated GIPSY-OASIS II package
– “Differential positions” computed by use of National Geodetic
Survey/NOAA’s PAGES package
– All processed using IGS orbital coordinate data
• Footprint array surveys
– Software packages used include
• GPSurvey V2.3
• Ashtech GPPS
• Magellan AOS
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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
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