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Data Set ID:
IMCS31B

IceBridge Scintrex CS-3 Cesium Magnetometer L1B Geolocated Magnetic Anomalies, Version 2

This data set contains magnetic field readings taken over Antarctica using the Scintrex CS-3 Cesium Magnetometer instrument. The data were collected as part of Operation IceBridge funded aircraft survey campaigns.

This is the most recent version of these data.

Version Summary:

Major Version 2 data, beginning 18 November 2013, are in Comma Separated Value ASCII files with associated XML files.

Version 1 data for 2012 and earlier campaigns are in Geosoft XYZ ASCII format.

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Parameter(s):
  • Geomagnetism > Magnetic Field
Data Format(s):
  • ASCII Text
Spatial Coverage:
N: -63, 
S: -90, 
E: 180, 
W: -180
Platform(s):P-3B
Spatial Resolution:
  • Varies x Varies
Sensor(s):CS-3
Temporal Coverage:
  • 18 November 2013 to 25 November 2017
Version(s):V2
Temporal ResolutionVariesMetadata XML:View Metadata Record
Data Contributor(s):James Cochran, Nicholas Frearson, Kirsteen Tinto, Bethany Burton

Geographic Coverage

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As a condition of using these data, you must cite the use of this data set using the following citation. For more information, see our Use and Copyright Web page.

Cochran, J. R., B. Burton, N. Frearson, and K. Tinto. 2014. IceBridge Scintrex CS-3 Cesium Magnetometer L1B Geolocated Magnetic Anomalies, Version 2. [Indicate subset used]. Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center. doi: https://doi.org/10.5067/OY7C2Y61YSYW. [Date Accessed].

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Detailed Data Description

Each Comma Separated Value (CSV) file contains data from a single flight. The data have not been broken into flight lines and include the flight target transects at the nominal draped flight altitude of 1,500 feet Above Ground Level (AGL) as well as the transit sections flown at high-altitude, nominally 16,000 ft. Above Sea Level (ASL). The ascent from takeoff to a level flying altitude and final descent from each flight have been removed.

Format

The data are in ASCII CSV file format.

Note: Currently IMCS31B data for 2011 through 2012 are in Geosoft XYZ ASCII format stored separately as IMCS31B Version 1. Beginning with the 2013 Antarctica campaign, all data are provided in CSV format. In the near future, data from all campaigns prior to Fall 2013 will be replaced with CSV data and added to Version 2. For details on the Version 1 data, see the Version 1 documentation.

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File Naming Convention

Example file names:

IMCS31B_V02_18112013_A.csv
IMCS31B_V02_18112013_A.csv.xml

Files are named according to the following convention, which is described in more detail in Table 1.

IMCS31B_Vnn_DDMMYYYY_A.xxx

Table 1. File Naming Convention
Variable Description
IMCS31B Short name for IceBridge Scintrex CS-3 Cesium Magnetometer L1B Geolocated Magnetic Anomalies
Vnn Data product version number. V02 = Version 2
DD Two-digit day
MM Two-digit month
YYYY Four-digit year
A Placeholder for multiple files generated from a single flight.
.xxx Indicates CSV ASCII text data file (.csv) or XML metadata file (.xml)
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File Size

The total data file volume is approximately 1.2 GB.

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Spatial Coverage

The spatial coverage includes Antarctica:

Southernmost Latitude: 90° S
Northernmost Latitude: 53° S
Westernmost Longitude: 180° W
Easternmost Longitude: 180° E

Spatial Resolution

Spatial resolution of the data is variable, chiefly from the variable line spacing of flight tracks. At an average flight speed of 240 knots (~120 m/s) the 20 Hz data rate gives a measurement approximately every 6 m along the ground. However, the flight elevation of ~500 m AGL places the plane at least 500 m from the source of the magnetic anomaly, and commonly much greater, as ice thicknesses can be greater than 3000 m. Therefore the along-track spatial resolution of the data is limited primarily by the spreading of the field with distance from source and tends to be ~1000 m.

Projection and Grid Description

Ellipsoid height WGS-84 (height above GRS 80 ellipsoid).

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Temporal Coverage

18 November 2013 to 25 November 2017

Temporal Resolution

IceBridge campaigns are conducted on an annually repeating basis. Arctic and Greenland campaigns are typically conducted during March, April, and May; Antarctic campaigns are typically conducted during October and November.

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Parameter or Variable

The data files contain data parameters as described in Table 2, plus header information including column headings, flight number, date, and line number.

Table 2. Parameter Description and Units
Column Description Units
FLIGHT Flight number Number
TIME UTC time HH:MM:SS.ss
TIME_SEC UTC seconds past midnight (continuous) Seconds
DATE UTC date YYYY/MM/DD
LAT Latitude WGS-84 Decimal degrees
LONG Longitude WGS-84 Decimal degrees
ELLHT Ellipsoid height WGS-84; height above Geodetic Reference System 1980 (GRS80) ellipsoid Meters
TFDSPK Despiked total magnetic field reading from cesium sensor nanoTesla (nT)
TFCOMP Despiked and compensated total magnetic field nT
DCOR# Diurnal correction value calculated from # base station(s). The number indicated in the DCOR# column heading, e.g. DCOR2, indicates the number of XXX_30MIN data columns that will appear at the end of the file. nT
IGRF International Geomagnetic Reference Field model IGRF2010 value based on flight date nT
MAGANOM Magnetic anomaly data (despiked, compensated, diurnally corrected, & IGRF removed) nT
MAGBW5K MAGANOM with Butterworth filter (8th degree filter with 5000 m central wavelength cutoff) nT
MCM_30MIN MAGANOM with Butterworth filter (8th degree filter with 5000 m central wavelength cutoff) nT
XXX_30MIN Magnetic base station data with 30-minute low-pass filter applied. XXX is the code for the base station used. More than one base station may be applied to a single flight. nT

The coordinates are the location of the center arm of the gravimeter during flight.

The in-line GPS-magnetic sensor offset is -22.6 m.

Null or unavailable data are denoted by '-999999'.

Sample Data Record

The sample shows the first six records of the IMCS31B_27112013_A.csv data file. Each record is wrapped to two lines to display on the page.

sample data record

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Software and Tools

The data files may be opened by any ASCII text reader.

Quality Assessment

Data quality was assessed during the 2011 Operation IceBridge campaign by comparing the magnetic anomaly calculated from measurements made during six repeats of a survey line between Thule and Camp Century. Individual profiles were differenced from the mean of all six repeats and the standard deviation of the differences was 7 nT.

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Data Acquisition and Processing

Theory of Measurements

The CS3 magnetometer is a passive sensor that records the variation in total field strength of the magnetic field across the survey area during flight. Data are corrected for temporal (diurnal) variation of Earth's field using fixed base stations, either those established specifically for each survey campaign or from the global INTERMAGNET network of permanent magnetic observatories. The magnetic field of the moving airframe is accounted for with a compensation correction, that accounts for variation in both heading and aircraft maneuvers.

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Data Acquisition Methods

2013 Antarctica Data

The total field airborne magnetic data were acquired with a Scintrex CS-3 cesium vapor magnetometer and the fluxgate magnetic data were acquired with a Billingsley TFM100G2 magnetometer. Level 1B processed magnetic data are provided at a 20Hz sample rate.

Table 3. 2013 Base Stations
Location Site ID Lat Long Elevation Median Value Sample Rate INTERMAGNET/USGS
McMurdo station, Antarctica MCM 77.85°S 166.68°E 91 m 62123 nT 3 sec USGS
Eyrewell, New Zealand EYR 43.42°S 172.35°E 120 m 57570 nT 1 min INTERMAGNET
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Derivation Techniques and Algorithms

Raw data from the magnetometer (from the IceBridge Scintrex CS-3 Cesium Magnetometer L0 Raw Magnetic Field data set) report the total magnetic field recorded by the magnetometer. The processing steps for reducing these data to Level-1B magnetic anomalies are described in the Processing Steps section below. Step TFCOMPF accounts for the variation in the magnetic field caused by the airframe maneuvering through Earth's field. The compensation coefficients used are established from the results of a compensation flight, flown at the start of each campaign. The compensation pattern is a square, flown at high elevation (10,000 ft. AGL) in an area of low magnetic gradient. A series of manoeuvres are flown on each of the four headings of the square.

  1. rolls: 10 degrees right bank followed by 10 degrees left bank for 3 oscillations
  2. pitches: 5 degrees nose up followed by 5 degrees nose down for 3 oscillations
  3. yaws: 5 degrees nose left followed by 5 degrees nose right for 3 oscillations

The period of each complete oscillation (+,-, back to level) is ~5 seconds. The maneuvers are smooth, and the flight altitude is held as constant as possible.

These maneuvers record the variation of the measured field due to the movement of the airframe through Earth's magnetic field. The total magnetic field is measured by the Cesium magnetometer, and the x, y and z components of the field are measured by the Billingsley fluxgate magnetometer. Compensation coefficients are established from the compensation pattern and applied to the total measured field in the raw data using proprietary PicoEnvirotec PEIComp software. Raw data from the compensation flights are available in the IceBridge Scintrex CS-3 Cesium Magnetometer L0 Raw Magnetic Field data set. Compensation values in these data sets are small, and typically less than 10 nT.

Trajectory and Attitude Data

The provided coordinates are the location of the center arm of the gravimeter during flight. The required in-line GPS-magnetic sensor offset is -22.6 meters.

Processing Steps

The magnetic data were processed by the U. S. Geological Survey (USGS), Crustal Geophysics and Geochemistry Science Center, Denver, Colorado.

DCOR#: Multiple base stations were used where applicable and when data were available using the usgs_mbase.gx available in Geosoft Oasis montaj (Phillips, 2007). A median value was calculated for each base station by averaging quiet-time readings, typically around local midnight, for each day data were available throughout the survey.

TFDSPK: The total field and fluxgate data were despiked initially based on selected threshold fourth difference values and then manually despiked further to remove interference from intermittent high-frequency (HF) radio communications during the flights.

TFCOMP: Two magnetic compensation flights were flown in 2011; one from Kangerlussuaq (flight 115) and one from Thule (flight 131). A single magnetic compensation flight was flown in 2012 from Kangerlussuaq (flight 232). Due to time constraints, a second compensation flight from Thule was not flown in 2012, so the compensation coefficients from the 2011 Thule compensation flight were used. In 2013, a compensation flight was flown during the check flight, prior to the first survey flight (flight 901 on UTC date Nov. 17). A single set of compensation coefficients was applied to each flight based on the flight's path and its proximity to the compensation boxes. Because the flight data have not been separated into flight lines, artifacts from the compensation coefficient corrections are present in the turns where heading variations are greatest.

TFPROC = TFCOMP - DCOR# - IGRF

MAGANOM = TFCOMP - DCOR# - IGRF

TFBW5K: An eighth-order, low-pass Butterworth filter with a 5000 m central wavelength cutoff was applied to the TFPROC channel to remove high-frequency signal and to minimize the compensation artifacts. This channel is only in the 2011 Level-1B data set (see the IceBridge Scintrex CS-3 Cesium Magnetometer L1B Geolocated Magnetic Anomalies, Version 1, data set).

MAGBW5K: An eighth-order, low-pass Butterworth filter with a 5000 m central wavelength cutoff was applied to the MAGANOM channel to remove high-frequency signal and to minimize the compensation artifacts. The MAGBW5K channel is the same as the TFBW5K channel in the 2011 Level-1B data set.

Tables 4, 5, and 6 summarize 2011, 2012, and 2013 flight processing and base stations.

Table 4. 2011 Flight Processing Summary
Flight Number Flight Name Date Compensation Base Station(s)
101 Sea Ice Connor Corridor 16 March Thule BRW,RES,THL
102 Sea Ice CryoSat-2 Underflight 17 March Thule BRW,HRN,RES,THL
103 Sea Ice ZigZag West 18 March Thule HRN,RES,THL
104 North Basin Transect/Thule-Fairbanks 22 March Thule BRW,CMO,RES,THL
105 Sea Ice - ICEX Camp Survey/Fairbanks 23 March Thule BRW,CMO
106 South Basin Transect/Fairbanks-Thule 25 March Thule BRW,CMO,RES,THL
107 Sea Ice ZigZag East

26 March

 Thule HRN,THL
108 Sea Ice Fram Gateway 28 Marcy Thule HRN,THL
109 CryoSat Land ice 29 Marcy Thule GDH,THL
110 Jakobshavn 02/Thule-Kangerlussuaq 31 March Thule GDH,THL
111 No flight data, flight was aborted before takeoff 5 April
112 Jakobshavn 01 6 April Kangerlussuaq GDH,KNG
113 Umanaq 01 7 April Kangerlussuaq GDH,KNG
114 SW Mopup 01 8 April Kangerlussuaq KNG
115 Magnetic compensation and radar calibration 9 April Kangerlussuaq KNG
116 SE Glaciers Mopup 01 9 April Kangerlussuaq KNG,NAQ
117 SE Coastal 02 12 April Kangerlussuaq KNG,NAQ
118 Russell 02 Mopup 13 April Kangerlussuaq KNG
119 SE Flank 01 14 April Kangerlussuaq KNG,NAQ
120 Sea Ice CryoVEx 15 April Kangerlussuaq THL
121 SW Mopup 02 16 April Kangerlussuaq KNG
122 SE Fjords 01 18 April Kangerlussuaq KNG,NAQ
123 Helheim-Kangerdlugssuaq 19 April Kangerlussuaq KNG
124 Jakobshavn/Lakes 22 April Kangerlussuaq GDH,KNG
125 Umanaq 02 23 April Kangerlussuaq GDH,KNG
126 Duck-Clusters 25 April Kangerlussuaq KNG
127 Geikie 01 26 April Kangerlussuaq GDH,KNG
128 Baffin Bay Sea Ice 28 April Thule GDH,THL
129 Petermann 03 29 April Thule TGS
130 NEIS 04 2 May Thule HRN,THL
131 Magnetic compensation 4 May Thule THL
132 Devon Ice Cap - CryoVEx 5 May Thule RES,THL
133 Layers NEEM-NGRIP 6 May Thule THL
134 Petermann 02 7 May Thule THL
135 North Glaciers 9 May Thule HRN,THL
136 Ellesmere Island 01 10 May Thule RES,TGS
137 NW Coastal 04 11 May Thule GDH,THL
138 Barnes Ice Cap/Bylot Island 12 May Thule THL
139 NW Glaciers 13 May Thule GDH,THL
140 NW Coastal 05 16 May Thule GDH,THL
Table 5. 2012 Flight Processing Summary
Flight Number Flight Name Date Compensation Base Station(s)
201 Sea Ice - North Basin Transect 2012/03/14 Thule THL,CMO
202 Sea Ice - Beaufort-Chukchi Zigzag 2012/03/15 Thule CMO
203 Sea Ice - Beaufort-Chukchi Diamond 2012/03/16 Thule BRW,CMO
204 Sea Ice - Alaskan Coastal Zigzag A 2012/03/17 Thule CMO
205 Sea Ice - South Basin Transect 2012/03/19 Thule TGS,CMO
206 Sea Ice - North Pole Transect 2012/03/21 Thule TGS
2071 Sea Ice - Connor Corridor 2012/03/22 Thule TGS,RES
208a,b2 Sea Ice - Canada Basin 2012/03/23 Thule THL,RES
209 Sea Ice - Wingham Box 2012/03/26 Thule TGS,RES
210 Sea Ice - Zigzag East 2012/03/27 Thule TGS
211 Sea Ice - Cryosat 2012/03/28 Thule THL
212 Sea Ice - Zigzag West Cryovex 2012/03/29 Thule TGS
213 CryoSat Land 2012/03/30 Thule TGS,GDH
214 Sea Ice - Fram Gateway 2012/04/02 Thule TGS,HRN
2153 Gap-Summit 2012/04/04 Thule THL,GDH
216 Sea Ice - MABEL Underflight 2012/04/10 Kangerlussuaq KNG,HRN
217 East Glaciers 01 2012/04/11 Kangerlussuaq KNG
218 Geikie 02 2012/04/12 Kangerlussuaq KNG
219 East Central Grid 01 2012/04/13 Kangerlussuaq KNG
220 Helheim Kangerdlugssuaq Gap 01 2012/04/14 Kangerlussuaq KNG
221 Geikie 03 2012/04/16 Kangerlussuaq KNG
222 No flight data; flight aborted shortly after takeoff 2012/04/17
223 Helheim Kangerd 2012/04/17 Kangerlussuaq KNG
224 Southeast Mopup 01 2012/04/18 Kangerlussuaq KNG
225 East Central Grid 03 2012/04/19 Kangerlussuaq KNG,HRN
226 Southwest Coastal 01 2012/04/20 Kangerlussuaq KNG,NAQ
227 Disko Bay 01 2012/04/21 Kangerlussuaq KNG,GDH
228 Helheim Kangerdlugssuaq Gap 02 2012/04/23 Kangerlussuaq KNG
229 Southwest Glaciers 01 2012/04/25 Kangerlussuaq KNG,NAQ
230 Southeast Glaciers 01 2012/04/28 Kangerlussuaq KNG,NAQ
231 Jakobshavn Basin 01 2012/04/29 Kangerlussuaq KNG,GDH
232 Umanaq-Sarqardliupsermia (mag comp) 2012/04/30 Kangerlussuaq GDH
233 Jakobshavn 02 2012/05/02 Kangerlussuaq GDH,THL
234 North Glaciers 02 2012/05/03 Thule TGS,HRN
235 Devon 01 2012/05/04 Thule TGS,RES
236 Northeast Grid 02 2012/05/07 Thule HRN
237 Northeast Grid 03 2012/05/08 Thule HRN
238 Northwest Fjords 01 2012/05/09 Thule TGS,GDH
239 Cape Alexander 01 2012/05/10 Thule THL,TGS
240 Humboldt 01 2012/05/11 Thule THL
241 NEIS ICESat 2012/05/14 Thule TGS,HRN
242 Northwest Glaciers 2012/05/15 Thule THL,GDH
243 North Flux 01 2012/05/16 Thule TGS
244 Ellesmere 01 2012/05/17 Thule TGS,RES
Table 6. 2013 Flight Processing Summary
Flight Number Flight Name Date Compensation Base Station(s)
401 Land Ice - TAM West 2013/11/18 - 2013/11/19 MCM 401
402 Land Ice - Victoria 01 2013/11/19 - 2013/11/20 MCM 402
403 Sea Ice - Ross Sea Fluxgate 2013/11/20 - 2013/11/21 MCM 403
404 Land Ice - Siple Coast 03 2013/11/25 - 2013/11/26 MCM 404
405 Land Ice - Dome C – Vostok 2013/11/26 - 2013/11/27 MCM 402
406 Sea Ice - CryoSat /Christchurch Transit 2013/11/27 - 2013/11/28 MCM, EYR 406

1 The cesium sensor and pre-amplifier assembly were replaced between flights 207 and 208 to troubleshoot the data spikes in the total field data. It was later determined to be caused by the lack of a low-pass hardware filter being applied to the incoming data on the first logger (100 Hz sample rate).

2 Flight 208 data were acquired with two different data loggers: 208a and 208b were acquired at original sample rates of 100 Hz and 160 Hz, respectively.

3 Engine #3 was shut down at approximately 15:23:00 UTC time due to a malfunction, at which time the remainder of the planned survey was aborted and headed directly to Kangerlussuaq with only three operational engines. This engine was replaced between flights 215 and 216.

4 Data from DMC and VOS INTERMAGNET observatories were not available for this flight.

Version History

IMCS31B Version 1: Currently the IceBridge Scintrex CS-3 Cesium Magnetometer L1B Geolocated Magnetic Anomalies data for 2011 through 2012 are in Geosoft XYZ ASCII format stored separately as Version 1. In the near future, data from all campaigns prior to Fall 2013 will be replaced with CSV data and added to Version 2. For details on the Version 1 data, see the .

IMCS31B Version 2: Beginning with the 2013 Antarctica campaign, all data are provided in CSV format.

Error Sources

Major sources of error in magnetic surveys are unaccounted for temporal variations in the magnetic field during surveys, including geomagnetic storms. No magnetic storms were identified during these survey periods. The processing steps applied here correct for smooth diurnal variation of Earth's field, as recorded at fixed base stations. Survey data are despiked to remove high-frequency magnetic field variations, including those associated with aircraft communications.

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Sensor or Instrument Description

The Magnetics system includes a total field cesium sensor, a pre-amplifier, a three-axis fluxgate and a data acquisition system. The sensor is mounted at the end of a non-magnetic boom attached to the tail of the P-3B Orion aircraft. As the aircraft flies, the sensor measures the total incident magnetic field. The size of the signal is proportional to the magnitude of the field through which the sensor is flown and the rate at which the field is cut. Therefore, to extract the signal of the magnetic anomalies that the aircraft is flying over it is necessary to account for accelerations in the airframe, which are derived from the fluxgate data, the Earth's background field as defined by the IGRF, and the diurnal signal recorded on a fixed base station. The non-magnetic region of the tail-boom continues for approximately 20 ft rearwards of the tail of the aircraft. The sensor is connected to the pre-amp, located about 10 ft away inside the boom. The pre-amp regulates power to the sensor and sends a signal proportional to the magnetic flux passing by the sensor back to the data acquisition system. The data acquisition system is located in the Gravity rack inside the aircraft cabin where the data are time stamped and stored in the data acquisition system. The fluxgate is located inside the tail-boom away from both the sensor and the pre-amp.

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References and Related Publications

Phillips, J.D. 2007. Geosoft eXecutables (GX's) Developed by the U.S. Geological Survey, Version 2.0, with Notes on GX Development from Fortran code. U.S. Geological Survey Open-File Report 2007-1355. http://pubs.usgs.gov/of/2007/1355/

Related Data Collections

Related Web Sites

  • IceBridge Data Web site at NSIDC (http://nsidc.org/data/icebridge/index.html).
  • IceBridge Web site at NASA (http://www.nasa.gov/mission_pages/icebridge/index.html).
  • ICESat/GLAS Web site at NASA Wallops Flight Facility (http://glas.wff.nasa.gov/).
  • ICESat/GLAS Web site at NSIDC (http://nsidc.org/daac/projects/lidar/glas.html).

Contacts and Acknowledgments

James R. Cochran, Nicholas Frearson, Kirsteen Tinto
Lamont-Doherty Earth Observatory
109C Oceanography
61 Route 9W - PO Box 1000
Palisades, New York 10964-8000 USA

Carol Finn, Bethany L. Burton
United States Geological Survey
Crustal Geophysics and Geochemistry Science Center
Denver Federal Center, Bldg. 20, MS 964
Denver, CO 80225-0046 USA

Acknowledgments: 

This work was funded by NASA as part of Operation IceBridge awards NNX10AT69G and NNX13AD25A.

Document Information

DOCUMENT CREATION DATE

August 2014

DOCUMENT REVISION DATE

May 2019

No technical references available for this data set.

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