MIRAI MR03-K02 Gravity

Last Modified: 2012-12-25
: MR03-K02
: Processed (DMO)-Basic
: Absolute gravity
:
OCEANS > MARINE GEOPHYSICS > MARINE GRAVITY FIELD
SOLID EARTH > GEODETICS/GRAVITY > GRAVITY

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2003-05-21 06:21 – 2003-06-06 20:24

Instrument:
Shipboard gravimeter
Instrument:
Microgravimeter ( - MR11-05 Leg2)
The data provided here are absolute gravity data. The absolute gravity data are a combination of relative gravity data measured by the shipboard gravity meter and the absolute gravity data of the ports in departure and arrival. Drift corrections were done before converting into absolute gravity. The absolute gravity values of the ports are referenced to those of the Japan Gravity Standardization Net of the Geographical Survey Institute of Japan.
  1. (1) Shipboard gravity meter
  2. The system consists of two main assemblies; the gyro-stabilized platform including the gravity sensor and the data handling & control system.
    Manufacturer: LaCoste & Romberg
    Model: S-116
    Measuring range: 12,000 mGal
    Accuracy: 1.0 mGal
    Drift rate: < 3.0mGal/month
    Installation: Gravity meter room
    Reference:「Model "S" Air-Sea Dynamic Gravity Meter SystemⅡ」 INSTRUCTION MANUAL LaCoste and Romberg Gravity Meters, Inc. 2004
  3. (2) Portable gravity meter
  4. The portable gravity meter consists of two modules; the data acquisition/control module and the gravity sensor module. The gravity sensor is enclosed in a thermostatically controlled vacuum chamber. The portable gravity meter is used to calculate the absolute gravity of the port with reference to the gravity station of the Japan Gravity Standardization Net of the Geographical Survey Institute of Japan.
    Manufacturer: SCINTREX
    Model: CG-3M
    Measurement range: 7,000 mGal
    Standard deviation: 0.05 mGal
    Drift rate: < 0.02 mGal/day
    Reference:“CG-3M AUTOGRAV AUTOMATED GRAVITY METER OPERATOR MANUAL”, SCINTREX
Date (UTC) Port Absolute gravity (mGal) Sea level (cm) Draft shipboard (cm) Absolute gravity at sensor position (mGal) Reading of shipboard gravity meter (mGal)
2003/05/18 00:52:00 SEKINEHAMA 980371.85 238 605 980372.62 12666.6
2003/06/06 23:00:00 YOKOHAMA 979741.25 321 665 979742.30 12036.7
According to the filter process of the gravity meter system, the gravity data has a time lag of 300 seconds between the measurement and its output. After adjustment of this lag time, the following corrections and calculations were performed.

  1. (1) Drift correction
  2. D = ((Vge-Vgs)-(Age-Ags))/(Te-Ts)
    D: Drift value (mGal/day)
    Vgs: The shipboard gravity at the start of the cruise (mGal)
    Vge: The shipboard gravity at the end of the cruise (mGal)
    Ags: The absolute gravity at the shipboard sensor position at the start of the cruise (mGal)
    Age: The absolute gravity at the shipboard sensor position at the end of the cruise (mGal)
    Ts: The start time of the cruise (day)
    Te: The end time of the cruise (day)
  3. (2) Calculation of the absolute gravity
  4. G = Ags+(Vg-Vgs)-D*(T-Ts)+E+H*β
    G: The absolute gravity at sea surface (mGal)
    Ags: The absolute gravity at the shipboard sensor position at the start of the cruise (mGal)
    Vgs: The shipboard gravity at the start of the cruise (mGal)
    Vg: The shipboard gravity at the measurement time (mGal)
    D: Drift value (mGal/day)
    Ts: The start time of the cruise (day)
    T: The measurement time (day)
    E: Eoetvoes correction (mGal)
    H: Height from sea surface of the shipboard sensor position (m)
    β: Free-air gradient 0.3086 (mGal/m)
  5. (3) Output of the data
  6. Time (UTC)
    Latitude (degree)
    Longitude (degree)
    Processed absolute gravity (mGal)
    Depth (m)
(1) File naming rule: Cruise ID_p.grv
(2) Sampling rate: 1 minute
(3) If you would like the raw data set, please contact us from "Contact Us" above.
: MR03-K02
: Processed (DMO)-Basic
: Absolute gravity
:
OCEANS > MARINE GEOPHYSICS > MARINE GRAVITY FIELD
SOLID EARTH > GEODETICS/GRAVITY > GRAVITY

Observation Map

Data List

  File names
MR03-K02_p.grv
: MR03-K02
: Processed (DMO)-Basic

Gravity Processed

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 Latitude (degree) ; positive in north, negative in south
4 27 -36 Longitude f10.5 degree Longitude (degree) ; positive in east, negative in west
5 39 -46 Gravity f8.1 mGal
6 48 -52 Depth i5 m

Related Information

Update History

2012-12-25
An observation data was registerd.