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IceBridge Scintrex CS-3 Cesium Magnetometer L1B Geolocated Magnetic Anomalies, Version 2
The NASA IceBridge Scintrex CS-3 Cesium Magnetometer L1B Geolocated Magnetic Anomalies (IMCS31B) 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.
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.
|Data Contributor(s):||James Cochran, Nicholas Frearson, Kirsteen Tinto, Bethany Burton|
|Metadata XML:||View Metadata Record|
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: http://dx.doi.org/10.5067/OY7C2Y61YSYW. [Date Accessed].
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.
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.
Data are available on the FTP site in the
https://n5eil01u.ecs.nsidc.org/ICEBRIDGE/IMCS31B.002/ directory. Within this directory, the folders are organized by date, for example
The Level-1B Geolocated Magnetic Anomalies data files have the naming convention shown below. File name variables are described in Table 1.
||Short name for IceBridge Scintrex CS-3 Cesium Magnetometer L1B Geolocated Magnetic Anomalies|
||Data product version number|
||Placeholder for multiple files generated from a single flight.|
||Indicates CSV ASCII text data file (.csv) or XML file (.xml)|
CSV files range from approximately 14 KB to 95 KB.
XML files range from approximately 53 MB to 73 MB.
The entire data set is approximately 405 MB.
Spatial coverage for the IceBridge Scintrex CS-3 Cesium Magnetometer L1B Geolocated Magnetic Anomalies Version 2 2013 data includes Antarctica.
Southernmost Latitude: 90° S
Northernmost Latitude: 53° S
Westernmost Longitude: 180° W
Easternmost Longitude: 180° E
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).
These data were collected from 18 November 2013 to 29 November 2013 as part of Operation IceBridge funded campaigns.
IceBridge campaigns are conducted on an annual repeating basis. Arctic and Greenland campaigns are conducted during March, April, and May, and Antarctic campaigns are conducted during October and November.
The data files contain data parameters as described in Table 2, plus header information including column headings, flight number, date, and line number.
|TIME_SEC||UTC seconds past midnight (continuous)||Seconds|
|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.
Software and Tools
The data files may be opened by any ASCII text reader.
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.
Data Acquisition and Processing
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.
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.
|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|
Raw data from the magnetometer (IceBridge Scintrex CS-3 Cesium Magnetometer L0 Raw Magnetic Field (IMCS30)) 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.
- rolls: 10 degrees right bank followed by 10 degrees left bank for 3 oscillations
- pitches: 5 degrees nose up followed by 5 degrees nose down for 3 oscillations
- 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 IceBridge Scintrex CS-3 Cesium Magnetometer L0 Raw Magnetic Field (IMCS30). 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.
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 IceBridge Scintrex CS-3 Cesium Magnetometer L1B Geolocated Magnetic Anomalies (IMCS31B) Version 1).
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.
|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||
|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|
|125||Umanaq 02||23 April||Kangerlussuaq||GDH,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|
|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|
|214||Sea Ice - Fram Gateway||2012/04/02||Thule||TGS,HRN|
|216||Sea Ice - MABEL Underflight||2012/04/10||Kangerlussuaq||KNG,HRN|
|217||East Glaciers 01||2012/04/11||Kangerlussuaq||KNG|
|219||East Central Grid 01||2012/04/13||Kangerlussuaq||KNG|
|220||Helheim Kangerdlugssuaq Gap 01||2012/04/14||Kangerlussuaq||KNG|
|222||No flight data; flight aborted shortly after takeoff||2012/04/17|
|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|
|234||North Glaciers 02||2012/05/03||Thule||TGS,HRN|
|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|
|243||North Flux 01||2012/05/16||Thule||TGS|
|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.
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 .
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.
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.
References and Related Publications
Contacts and Acknowledgments
James R. Cochran, Nicholas Frearson, Kirsteen Tinto
Lamont-Doherty Earth Observatory
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
This work was funded by NASA as part of Operation IceBridge awards NNX10AT69G and NNX13AD25A.
DOCUMENT CREATION DATE
20 August 2014