MIRAI MR18-05C Shipboard Three Component Magnetometer (STCM)

Last Modified: 2019-08-26
: MR18-05C
: Processed (DMO)-Corrected
: JAMSTEC
: X, Y and Z component of geomagnetic field anomaly, Absolute value of geomagnetic field anomaly
:
OCEANS > MARINE GEOPHYSICS > MARINE MAGNETICS
SOLID EARTH > GEOMAGNETISM

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2018-10-24 07:25 – 2018-12-06 23:23

Instrument:
Three component magnetometer
The data provided is for corrected three component geomagnetic field anomalies. Three-axes flux-gate sensors with ring-cored coils were fixed on the roof of the bridge.
They measure the following items :
h-component : along track line component, positive for the bow direction pitch.
s-component : across track line component, positive for the starboard side roll.
v-component : vertical component, positive for the downward direction.
The effect of ship motion was eliminated by roll and pitch data which was provided by a tilt sensor. The apparent magnetic influence can be detected through a "Figure of 8 turn"(a pair of clockwise and anti-clockwise turns) on each cruise. If no Figure of 8 turn on the cruise was completed, the latest Figure of 8 turn from the previous cruise was applied. As a quality control, data of low reliability was removed (see Data processing for quality control criteria). Synthetic geomagnetic field values were calculated from IGRF models.
(1) Magnetometer
Manufacturer : Tierra Technica Ltd.
Type : SFG1214
Measurement range : ±100,000 nT
Accuracy : less than 100 nT
Resolution : 1 nT
Location : Dry Laboratory

(2) Magnetic Sensor
Manufacturer : Tierra Technica Ltd.
Form : flux-gate sensors with ring-cored coils
Location : Foremast

(3) Attitude sensor and Gyro compass
Manufacturer : IXBLUE
Type : PHINS
Accuracy(Roll, Pitch) : 0.01 degree
Accuracy(Gyro) : 0.01 degree *Secant(Lat.)
Location : In the doppler radar dome
In MR18-05C cruise
Date (UTC)
2018/11/11 04:30:00 - 2018/11/11 04:55:00
2018/12/04 09:01:00 - 2018/12/04 09:26:00
The following corrections and calculations were performed.

(1) Ship magnetization correction
  Hob = ARPYF + Hp ---(i)
Hob : Observed magnetic field vector (Ship coordinates)
A : Effect of induced magnetization of the ship
R : Matrix of rotation due to the roll
P : Matrix of rotation due to the pitch
Y : Matrix of rotation due to the heading
F : Geomagnetic field vector
Hp : Ship's permanent magnetic moment

Following the equation(i), we calculate the geomagnetic field F.
  RPYF = BHob + Hbp ---(ii)
B : coefficient of Figure of 8 turn
Hbp : Permanent magnetic field vector of the ship

Reference : Isezaki,N., A new shipboard three-component magnetometer, GEOPHYSICS. VOL.51,NO10(1986);P1992-1998

(2) International Geomagnetic Reference Field (IGRF)
Synthetic geomagnetic field values are calculated from IGRF 12th Generation models by using navigation data ; latitude, longitude and date.
Reference : IAGA Division V-MOD Geomagnetic Field Modeling[http://www.ngdc.noaa.gov/IAGA/vmod/igrf.html]

(3) Calculation of the geomagnetic field anomaly
  An = F - Figrf
An : Geomagnetic field anomaly vector
F : Geomagnetic field vector
Figrf : Synthetic geomagnetic field vector from IGRF

(4) Quality control of data
Following criteria were used for removal of data of low reliability:
・Time error (inversion of time, continuation of same timestamps)
・Summation of the difference of heading by one second exceeding 20 degree per 5 minutes
・Ground speed of the ship below 3knot or exceeding 20knot
・X, Y, or Z component of geomagnetic field anomaly exceeding ±4000nT

(5) Filtering of the geomagnetic field anomaly
Due to the residual undulation of the ship, a 120 second length Gaussian filter was applied for each component of the geomagnetic field anomaly data.

(6) Output of the data
Time (UTC)
Latitude (degree)
Longitude (degree)
X : Northward (positive on the north) component of geomagnetic field anomaly (nT)
Y : Eastward (positive on the east) component of geomagnetic field anomaly (nT)
Z : Vertical (positive for downward) component of geomagnetic field anomaly (nT)
T : Absolute value of geomagnetic field anomaly (nT)
This coefficient was calculated from the above-mentioned Figure of 8 turn
  | 0.9954 0.0302 0.0407 |   | 3338.3300 |
B = | -0.0314 1.0521 -0.0102 | Hbp = | -638.1280 |
  | 0.0389 0.0016 0.9923 |   | 46.7736 |
(1) File naming rule : Cruise ID_corr.stcm
(2) Sampling rate : 10 seconds
(3) Geodetic system : WGS84
(4) If you would like the raw data set, please contact us from "Contact Us" above.
: MR18-05C
: Processed (DMO)-Corrected
: JAMSTEC
: X, Y and Z component of geomagnetic field anomaly, Absolute value of geomagnetic field anomaly
:
OCEANS > MARINE GEOPHYSICS > MARINE MAGNETICS
SOLID EARTH > GEOMAGNETISM

Observation Map

Imagery reproduced from ...

Figures

Data List

  File names
MR18-05C_corr.stcm
: MR18-05C
: Processed (DMO)-Corrected
: JAMSTEC

STCM Corrected

No. Column Content Format Unit Remarks
1 1 - 8 Date i4,i2,i2 YYYYMMDD (UTC)
2 10 -15 Time i2,i2,i2 hhmmss (UTC)
3 17 -25 Latitude f9.5 degree No sign for the northern hemisphere.
Negative for the southern hemisphere.
4 27 -36 Longitude f10.5 degree No sign for eastern hemisphere.
Negative for the western hemisphere.
5 38 -43 X component of geomagnetic field anomaly f6.0 nT Positive on the north
6 45 -50 Y component of geomagnetic field anomaly f6.0 nT Positive on the east
7 52 -57 Z component of geomagnetic field anomaly f6.0 nT Positive for downward
8 59 -64 Absolute value of geomagnetic field anomaly f6.0 nT

Related Information

Update History

2019-08-26
An observation data was registerd.
2019-06-11
An observation data was registerd.