Identification_Information:
  Citation:
    Citation_Information:
      Originator: U.S. Geological Survey
      Publication_Date: Unknown
      Title: Aeromagnetic and gravity data of the Central Transantarctic
Mountains
      Series_Information:
        Series_Name: U.S. Geological Survey Open-File Report
        Issue_Identification: OFR 06-1255
      Publication_Information:
        Publication_Place: Denver, CO
        Publisher: U. S. Geological Survey
  Description:
    Abstract: Near complete coverage of the East Antarctic Shield by ice hampers
geological study of crustal architecture important for understanding global
tectonic and climate history. Limited exposures in the central Transantarctic
Mountains (CTAM), however, show that Archean and Proterozoic rocks of the shield
as well as Neoproterozoic-lower Paleozoic sedimentary successions were involved
in oblique convergence associated with Gondwana amalgamation. Subsequently, the
area was overprinted by Jurassic magmatism and Cenozoic uplift. To extend the
known geology of the region to ice-covered areas, we conducted an aeromagnetic
survey flown in draped mode by helicopters over the Central Transantarctic
Mountains and by fixed-wing aircraft over the adjacent polar plateau. We flew
more than 32,000 line km covering an area of nearly 60,000 km2 at an average
altitude of 600 m, with average line spacing 2.5 km over most areas and 1.25 km
over basement rocks exposed in the Miller and Geologists ranges. Additional
lines flown to the north, south, and west extended preliminary coverage and tied
with existing surveys. Gravity data was collected on the ground along a central
transect of the helicopter survey area.
    Purpose: From December 2003 to January 2004, the CTAM group flew a
helicopter and twin-otter aeromagnetic survey and collected ground gravity
station data along a profile.  These data will be integrated with other geologic
and geophysical data in order to extend the known geology of the region to
ice-covered areas.
  Time_Period_of_Content:
    Time_Period_Information:
      Single_Date/Time:
        Calendar_Date: unknown
        Time_of_Day: unknown
    Currentness_Reference: publication date
  Status:
    Progress: Complete
    Maintenance_and_Update_Frequency: As needed
  Spatial_Domain:
    Bounding_Coordinates:
      West_Bounding_Coordinate: 139.275383
      East_Bounding_Coordinate: 170.218440
      North_Bounding_Coordinate: -82.357327
      South_Bounding_Coordinate: -83.952338
  Keywords:
    Theme:
      Theme_Keyword_Thesaurus: none
      Theme_Keyword: Gravity
      Theme_Keyword: Magnetic Anomalies
      Theme_Keyword: Magnetic Field
      Theme_Keyword: Magnetic Intensity
      Theme_Keyword: Tectonic Landforms
      Theme_Keyword: Tectonic Processes
    Theme:
      Theme_Keyword_Thesaurus: none
      Theme_Keyword: Transantarctic Mountains
      Theme_Keyword: TAM
      Theme_Keyword: geophysical data
      Theme_Keyword: aeromagnetic data
      Theme_Keyword: aeromagnetic grid
      Theme_Keyword: gravity data
    Theme:
      Theme_Keyword_Thesaurus: none
      Theme_Keyword: English
    Place:
      Place_Keyword_Thesaurus: none
      Place_Keyword: Antarctica
      Place_Keyword: Transantarctic Mountains
  Access_Constraints: None
  Use_Constraints: None.  Acknowledgement of the U.S. Geological Survey (USGS),
German Federal Institute for Geosciences and Natural  Resources  (BGR), and the
National Science Foundation would be appreciated in products derived from these
data.
  Point_of_Contact:
    Contact_Information:
      Contact_Person_Primary:
        Contact_Person: Eric D. Anderson
        Contact_Organization: U. S. Geological Survey
      Contact_Position: Geologist
      Contact_Address:
        Address_Type: mailing address
        Address: U.S. Geological Survey
        Address: Box 25046 Mail Stop 964
        Address: Denver Federal Center
        City: Denver
        State_or_Province: Colorado
        Postal_Code: 80225-0046
        Country: USA
      Contact_Voice_Telephone: (303) 236-5652
      Contact_Facsimile_Telephone: (303) 236-1425
      Contact_Electronic_Mail_Address: ericanderson@usgs.gov
  Data_Set_Credit: This project was funded by the National Science Foundation,
Grant No. 0232042 and was in collaboration with scientists from the U. S.
Geological Survey (USGS), German Federal Institute for Geosciences and Natural 
Resources  (BGR) and University of Minnesota, Duluth.
  Native_Data_Set_Environment: Microsoft Windows XP Version 5.1 (Build 2600)
Service Pack 1; ESRI ArcCatalog 9.0.0.535
Data_Quality_Information:
  Attribute_Accuracy:
    Attribute_Accuracy_Report: The data in this file have been processed using
various formulas and methods that are not usually documented but that represent
industry standard practices for airborne data reduction.
  Logical_Consistency_Report:
    The data in this file were collected by a single contractor or group (CTAM)
who were responsible for collecting and processing the data.

    The data from this survey were collected using the same instruments
(magnetometers and navigational systems) throughout the survey and were
collected in a normal length of time with no long delays between survey
beginning and end.  Standard industry practices of the time were followed in
data collection and processing.

    A magnetic base station centrally located relative to the survey was
established on ice close to Moody Nunatak which recorded the daily variations of
Earth's magnetic field for removal from the total-field observed from the
airborne instrument.  The position of a cesium magnetometer carried in a bird
slung ~30 m below the helicopter was accomplished with Trimble 4000 GPS and
Ashtech Surveyor 12 receivers.  The data from each flight were quality
controlled.

    The crew for the aeromagnetic survey consisted of 4 helicopter pilots, 2
helicopter mechanics, 2 twin-otter pilots, 1 twin-otter mechanic, 6 scientists
(geophysicist, geologists and engineers), a mountaineer and various camp
operations staff.
  Completeness_Report: Loss of data due to poor transmission, channel dropout,
obvious spiking, missing channels, and other obvious errors were replaced with a
null value and subsequently interpolated.
  Positional_Accuracy:
    Horizontal_Positional_Accuracy:
      Horizontal_Positional_Accuracy_Report: Flight Path Recovery -
High-resolution horizontal position of the survey aircraft used to collect data
were determined from Global Positioning System (GPS) satellites.  Positioning
data were recorded in-flight independently using a Trimble GPS receiver.  For
some flights a differential position was calculated.  For the rest of the
flights an autonomous position was used.
      Quantitative_Horizontal_Positional_Accuracy_Assessment:
        Horizontal_Positional_Accuracy_Value: 20 m
        Horizontal_Positional_Accuracy_Explanation: Good to one meter when
differentially corrected.  Good to 20 meters when autonomous position was used.
    Vertical_Positional_Accuracy:
      Vertical_Positional_Accuracy_Report:
        Flight Path Recovery - High-resolution horizontal positions of the
survey aircraft used to collect data were determined from Global Positioning
System (GPS) satellites.  Positioning data were recorded in-flight independently
using a Trimble GPS and Ashtech Surveyor 12 receiver.  For some flights a
differential position was calculated.  For the rest of the flights an autonomous
position was used.

        The magnetometer was hung below the aircraft using a cable.  This data
set was collected as a draped survey having average terrain clearance of 600 m. 
Because aircraft, especially airplanes, cannot safely maintain a constant
terrain clearance, error in vertical position is introduced.
      Quantitative_Vertical_Positional_Accuracy_Assessment:
        Vertical_Positional_Accuracy_Value: 20 m
        Vertical_Positional_Accuracy_Explanation: Good to one meter when
differentially corrected.  Good to 20 meters when autonomous position was used.
  Lineage:
    Process_Step:
      Process_Description:
        USGS and BGR personnel used the Geosoft software package Oasis Montaj
version 5.1.6 to process the data.  Standard quality control (QC) procedures
were administered.  Latitude, longitude and magnetic values were checked for
obvious errors or spikes and null values were assigned to such.  These points
were then assigned values through linear interpolation.  Horizontal positions
were converted to a Lambert Conformal Conic projection described under spatial
reference.  Vertical positions recorded by the GPS unit were converted from
orthometric elevation to ellipsoid height by adding the geoid model to the
orthometric elevation recorded in the receiver. 

        During helicopter operations two separate systems were flown
simultaneously.  One was controlled by the USGS and the other by the BGR.  QC
checks were performed by both groups.  The individual datasets were then merged
into a composite dataset where diurnal corrections and IGRF removal were
performed, as well as tie-line and microleveling adjustments computed using
standard Geosoft procedures with slight modifications to the microleveling
amplitude cutoff.
      Process_Date: Unknown
Spatial_Reference_Information:
  Horizontal_Coordinate_System_Definition:
    Planar:
      Map_Projection:
        Map_Projection_Name: Lambert Conformal Conic
        Lambert_Conformal_Conic:
          Standard_Parallel: -83.650000
          Standard_Parallel: -82.850000
          Longitude_of_Central_Meridian: 154.500000
          Latitude_of_Projection_Origin: -83.250000
          False_Easting: 300000.000000
          False_Northing: 175000.000000
      Planar_Coordinate_Information:
        Planar_Coordinate_Encoding_Method: coordinate pair
        Coordinate_Representation:
          Abscissa_Resolution: 625.000000
          Ordinate_Resolution: 625.000000
        Planar_Distance_Units: meters
    Geodetic_Model:
      Horizontal_Datum_Name: WGS_84
      Ellipsoid_Name: WGS_84
      Semi-major_Axis: 6378137.000000
      Denominator_of_Flattening_Ratio: 298.257224
Entity_and_Attribute_Information:
  Detailed_Description:
    Entity_Type:
      Entity_Type_Label: Longitude
      Entity_Type_Definition: Longitude WGS84
      Entity_Type_Definition_Source: self evident
    Attribute:
      Attribute_Definition: Longitude WGS84
      Attribute_Definition_Source: self evident
      Attribute_Domain_Values:
        Range_Domain:
          Range_Domain_Minimum: 128.745892093
          Range_Domain_Maximum: 169.69225
          Attribute_Units_of_Measure: decimal degrees
  Detailed_Description:
    Entity_Type:
      Entity_Type_Label: Latitude
      Entity_Type_Definition: Latitude WGS84
      Entity_Type_Definition_Source: self evident
    Attribute:
      Attribute_Definition: Latitude WGS84
      Attribute_Definition_Source: self evident
      Attribute_Domain_Values:
        Range_Domain:
          Range_Domain_Minimum: -87.117223185
          Range_Domain_Maximum: -79.920871861
          Attribute_Units_of_Measure: decimal degrees
  Detailed_Description:
    Entity_Type:
      Entity_Type_Label: x
      Entity_Type_Definition: Lambert Conformal Conic (2SP) Lat1 -82.85, Lat2
-83.65, LatO -83.25, LongO 154.5, FE 300000, FN 175000, Datum and Ellipsoid
WGS84, Local Datum Transform WGS84
      Entity_Type_Definition_Source: self evident
    Attribute:
      Attribute_Definition: Lambert Conformal Conic (2SP) Lat1 -82.85, Lat2
-83.65, LatO -83.25, LongO 154.5, FE 300000, FN 175000, Datum and Ellipsoid
WGS84, Local Datum Transform WGS84
      Attribute_Definition_Source: self evident
      Attribute_Domain_Values:
        Range_Domain:
          Range_Domain_Minimum: -59328.1568922
          Range_Domain_Maximum: 489059
          Attribute_Units_of_Measure: meters
  Detailed_Description:
    Entity_Type:
      Entity_Type_Label: y
      Entity_Type_Definition: Lambert Conformal Conic (2SP) Lat1 -82.85, Lat2
-83.65, LatO -83.25, LongO 154.5, FE 300000, FN 175000, Datum and Ellipsoid
WGS84, Local Datum Transform WGS84
      Entity_Type_Definition_Source: self evident
    Attribute:
      Attribute_Definition: Lambert Conformal Conic (2SP) Lat1 -82.85, Lat2
-83.65, LatO -83.25, LongO 154.5, FE 300000, FN 175000, Datum and Ellipsoid
WGS84, Local Datum Transform WGS84
      Attribute_Definition_Source: self evident
      Attribute_Domain_Values:
        Range_Domain:
          Range_Domain_Minimum: -257437.864195
          Range_Domain_Maximum: 539567.4249843
          Attribute_Units_of_Measure: meters
  Detailed_Description:
    Entity_Type:
      Entity_Type_Label: ellipsoid_elv
      Entity_Type_Definition: height of WGS84 ellipsoid
      Entity_Type_Definition_Source: self evident
    Attribute:
      Attribute_Definition: height of WGS84 ellipsoid
      Attribute_Definition_Source: self evident
      Attribute_Domain_Values:
        Range_Domain:
          Range_Domain_Minimum: 185.86
          Range_Domain_Maximum: 4680.8
          Attribute_Units_of_Measure: meters
  Detailed_Description:
    Entity_Type:
      Entity_Type_Label: DATE
      Entity_Type_Definition: date
      Entity_Type_Definition_Source: self evident
    Attribute:
      Attribute_Definition: date
      Attribute_Definition_Source: self evident
      Attribute_Domain_Values:
        Unrepresentable_Domain: compound
  Detailed_Description:
    Entity_Type:
      Entity_Type_Label: UTC
      Entity_Type_Definition: Universal Time Coordinated
      Entity_Type_Definition_Source: self evident
    Attribute:
      Attribute_Definition: Universal Time
      Attribute_Definition_Source: self evident
      Attribute_Domain_Values:
        Unrepresentable_Domain: compound
  Detailed_Description:
    Entity_Type:
      Entity_Type_Label: mag_field
      Entity_Type_Definition: total magnetic field
      Entity_Type_Definition_Source: self evident
    Attribute:
      Attribute_Definition: Despiked total magnetic field
      Attribute_Definition_Source: self evident
      Attribute_Domain_Values:
        Range_Domain:
          Range_Domain_Minimum: 57567.78
          Range_Domain_Maximum: 61912.346
          Attribute_Units_of_Measure: nanotesla (nT)
  Detailed_Description:
    Entity_Type:
      Entity_Type_Label: mag_field_lp
      Entity_Type_Definition: despiked total magnetic field with low pass filter
applied
      Entity_Type_Definition_Source: self evident
    Attribute:
      Attribute_Definition: despiked total magnetic field with low pass filter
applied
      Attribute_Definition_Source: self evident
      Attribute_Domain_Values:
        Range_Domain:
          Range_Domain_Minimum: 57567.78
          Range_Domain_Maximum: 61912.346
          Attribute_Units_of_Measure: nanotesla (nT)
  Detailed_Description:
    Entity_Type:
      Entity_Type_Label: base_station_raw
      Entity_Type_Definition: raw base station values
      Entity_Type_Definition_Source: self evident
    Attribute:
      Attribute_Definition: raw base station values
      Attribute_Definition_Source: self evident
      Attribute_Domain_Values:
        Range_Domain:
          Range_Domain_Minimum: 60159.3
          Range_Domain_Maximum: 60895.99796667
          Attribute_Units_of_Measure: nanotesla (nT)
  Detailed_Description:
    Entity_Type:
      Entity_Type_Label: base_station_sm
      Entity_Type_Definition: base station values smoothed by removing dropouts
and linearly interpolating with a spline filter
      Entity_Type_Definition_Source: self evident
    Attribute:
      Attribute_Definition: base station values smoothed by removing dropouts
and linearly interpolating with a spline filter
      Attribute_Definition_Source: self evident
      Attribute_Domain_Values:
        Range_Domain:
          Range_Domain_Minimum: 60174.86
          Range_Domain_Maximum: 60839.99998667
          Attribute_Units_of_Measure: nanotesla (nT)
  Detailed_Description:
    Entity_Type:
      Entity_Type_Label: diurnal_raw
      Entity_Type_Definition: mag_field_lp diurnally corrected with raw base
station data (60340-base_station+mag_field_lp, where 60340 represents an average
base station value)
      Entity_Type_Definition_Source: self evident
    Attribute:
      Attribute_Definition: mag_field_lp diurnally corrected with raw base
station data (60340-base_station)+mag_field_lp)
      Attribute_Definition_Source: self evident
      Attribute_Domain_Values:
        Range_Domain:
          Range_Domain_Minimum: 57616.40903
          Range_Domain_Maximum: 61859.546
          Attribute_Units_of_Measure: nanotesla (nT)
  Detailed_Description:
    Entity_Type:
      Entity_Type_Label: diurnal_sm
      Entity_Type_Definition: Mag_field_lp diurnally corrected with smoothed
base station data (60340-base_station+mag_field_lp, where 60340 represents an
average base station value)
      Entity_Type_Definition_Source: self evident
    Attribute:
      Attribute_Definition: Mag_field_lp diurnally corrected with smoothed base
station data (60340-base_station+mag_field_lp)
      Attribute_Definition_Source: self evident
      Attribute_Domain_Values:
        Range_Domain:
          Range_Domain_Minimum: 57617.16588333
          Range_Domain_Maximum: 61858.00126783
          Attribute_Units_of_Measure: nanotesla (nT)
  Detailed_Description:
    Entity_Type:
      Entity_Type_Label: IGRF
      Entity_Type_Definition: International Geomagnetic Reference Field for 10th
January 2004 - Model year 2000
      Entity_Type_Definition_Source: self evident
    Attribute:
      Attribute_Definition: International Geomagnetic Reference Field for 10th
January 2004 - Model year 2000
      Attribute_Definition_Source: self evident
      Attribute_Domain_Values:
        Range_Domain:
          Range_Domain_Minimum: 57681.96597918
          Range_Domain_Maximum: 62044.81844907
          Attribute_Units_of_Measure: nanotesla (nT)
  Detailed_Description:
    Entity_Type:
      Entity_Type_Label: mag_final_sm
      Entity_Type_Definition: final residual mag with smoothed base station and
IGRF removed (diurnal_sm-IGRF+60340, where 60340 represents an average base
station value)
      Entity_Type_Definition_Source: self evident
    Attribute:
      Attribute_Definition: final residual mag with smoothed base station and
IGRF removed (diurnal_sm-IGRF+60340)
      Attribute_Definition_Source: self evident
      Attribute_Domain_Values:
        Range_Domain:
          Range_Domain_Minimum: 60002.19268013
          Range_Domain_Maximum: 61041.48901929
          Attribute_Units_of_Measure: nanotesla (nT)
  Detailed_Description:
    Entity_Type:
      Entity_Type_Label: residual
      Entity_Type_Definition: Anomalous magnetic field (mag_final_sm-60340,
where 60340 represents an average base station value)
      Entity_Type_Definition_Source: self evident
    Attribute:
      Attribute_Definition: Anomalous magnetic field (mag_final_sm-60340)
      Attribute_Definition_Source: self evident
      Attribute_Domain_Values:
        Range_Domain:
          Range_Domain_Minimum: -337.807319871
          Range_Domain_Maximum: 701.4890192911
          Attribute_Units_of_Measure: nanotesla (nT)
  Detailed_Description:
    Entity_Type:
      Entity_Type_Label: leveled
      Entity_Type_Definition: Anomalous magnetic field tie-line leveled using
standard defaults with Geosoft software and microleveled using an amplitude of
10 nT as cutoff
      Entity_Type_Definition_Source: self evident
    Attribute:
      Attribute_Definition: Anomalous magnetic field tie-line leveled using
standard defaults with Geosoft software and microleveled using an amplitude of
10 nT as cutoff
      Attribute_Definition_Source: self evident
      Attribute_Domain_Values:
        Range_Domain:
          Range_Domain_Minimum: -315.693289269
          Range_Domain_Maximum: 576.1396095226
          Attribute_Units_of_Measure: nanotesla (nT)
  Overview_Description:
    Entity_and_Attribute_Overview:
      Each record contains the following 17 attributes:

      Longitude - Longitude WGS84 - Decimal degrees
      Latitude - Latitude WGS84 - Decimal degrees
      x - Local x coordinate - meters
      y - Local y coordinate - meters
      ellipsoid_elv - WGS84 ellipsoid elevation - Meters
      Date - Date data was collected - YYYY/MM/DD
      Time - Time data was collected - hh:mm:ss.ss
      mag_field - Despiked magnetic field value - Nanotesla
      mag_field_lp - Despiked magnetic field value with a low pass filter
applied to get rid of micropulsations caused by instrumentation - Nanotesla
      base_station_raw - raw base station value - Nanotesla
      base_station_sm - smoothed base station value - Nanotesla
      diurnal_raw - diurnal correction applied to mag_field_lp using raw base
station values - Nanotesla
      diurnal_smooth - diurnal correction applied to mag_field_lp using smoothed
base station values - Nanotesla
      IGRF - IGRF correction model 2000 - Nanotesla
      mag_final_sm - final mag with smoothed base station - Nanotesla
      residual - anomalous magnetic field - Nanotesla
      leveled - final leveled data - both tie-line and microleveling techniques
applied - Nanotesla

      Because the magnetic field of the earth varies diurnally, a stationary
base magnetometer is maintained on the ground during airborne surveying.  The
base magnetometer records changes in the magnetic field (in nanoTeslas) as a
function of time.  The magnetic changes may have an amplitude of 20 to 50
nanoTeslas.  If changes are more severe, as would occur from a magnetic storm,
surveying is discontinued or the data recorded are not used.  Diurnal variations
are then removed from the airborne magnetic data based on the common time.

      The airborne magnetometer is accurate to about 0.002 nanotesla (nT) at 1
Hz and 0.02 nT at 10 Hz, and the base magnetometer has an accuracy of 1 nT.  The
accuracy of the base-corrected airborne value therefore is near 1 nanoTeslas or
better.

      The total magnetic value is the despiked, diurnally-corrected magnetic
field minus a geomagnetic reference field (GRF), which is a long-wavelength
regional magnetic field.  The most commonly used reference field is determined
from a model developed by the International Association of Geomagnetism and
Aeronomy (IAGA).  The International Geomagnetic Reference Field (IGRF) is a
predictive model adopted at the beginning of a model period (e.g. in 1989 for
1990-1995).  After the model period, a revised definitive model is adopted, the
Definitive Geomagnetic Reference Field (DGRF). This is the preferred model to
use for removing regional magnetic fields.

      The temporal variations cannot be completely predicted, thus error arises
in the application of the IGRF reductions.  These errors cannot be evaluated
until the release of the DGRF, a minimum of five years after the IGRF release. 
This field is issued to best describe the configuration of the earth's past
magnetic field.

      For this survey, the field removed was the IGRF model 2000.
    Entity_and_Attribute_Detail_Citation:
      Nettleton, L.L., 1971, Elementary Gravity and Magnetics for Geologists and
Seismologists: Society of Exploration Geophysicists Monograph Series No. 1, p.
83-87.

      Dobrin, M.B., 1976, Introduction to Geophysical Prospecting: New York,
McGraw-Hill Book Company, p. 505-517.
Distribution_Information:
  Distributor:
    Contact_Information:
      Contact_Person_Primary:
        Contact_Person: Eric D. Anderson
        Contact_Organization: U. S. Geological Survey
      Contact_Position: Geologist
      Contact_Address:
        Address_Type: mailing address
        Address: U.S. Geological Survey
        Address: Box 25046 Mail Stop 964
        Address: Denver Federal Center
        City: Denver
        State_or_Province: CO
        Postal_Code: 80225-0046
        Country: USA
      Contact_Voice_Telephone: (303) 236-5652
      Contact_Facsimile_Telephone: (303) 236-1425
      Contact_Electronic_Mail_Address: ericanderson@usgs.gov
  Resource_Description: Downloadable Data
  Distribution_Liability: Although all data published on this website have been
used by the USGS, no warranty, expressed or implied, is made by the USGS as to
the accuracy of the data and related materials.  The act of distribution shall
not constitute any such warranty, and no responsibility is assumed by the USGS
in the use of these data or related materials.
Metadata_Reference_Information:
  Metadata_Date: 20050204
  Metadata_Contact:
    Contact_Information:
      Contact_Person_Primary:
        Contact_Person: Eric D. Anderson
        Contact_Organization: U. S. Geological Survey
      Contact_Position: Geologist
      Contact_Address:
        Address_Type: mailing address
        Address: U.S. Geological Survey
        Address: Box 25046 Mail Stop 964
        Address: Denver Federal Center
        City: Denver
        State_or_Province: CO
        Postal_Code: 80225-0046
        Country: USA
      Contact_Voice_Telephone: (303) 236-5652
      Contact_Facsimile_Telephone: (303) 236-1425
      Contact_Electronic_Mail_Address: ericanderson@usgs.gov
  Metadata_Standard_Name: FGDC Content Standards for Digital Geospatial Metadata
  Metadata_Standard_Version: FGDC-STD-001-1998
  Metadata_Time_Convention: local time
  Metadata_Extensions:
    Online_Linkage: http://www.esri.com/metadata/esriprof80.html
    Profile_Name: ESRI Metadata Profile