The magnetic equator is also called "geomagnetic equator".It refers to the line connecting the points on the earth surface where the magnetic dip angle is zero.It does not coincide with the geographical equator.The horizontal component of the geomagnetic field on this line is equal togeomagnetic fieldSelf strength.The magnetic equator is not a strict geometric circle on the surface, but is uneven.The average magnetic field on the magnetic equator is 27.06~27.85 A · m.From the magnetic equator to the two magnetic poles,Magnetic dipGradually increase from 0 ° to 90 °.[1]
processing method
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Geomagnetic pole reduction is one of the most basic methods for processing magnetic survey data. It can eliminate or reduce the effect of oblique magnetization, improve the understanding and interpretation level of magnetic survey dataMagnetic anomalyIt is of great significance.However, at low latitudes, especially at the magnetic equator, the depolarization process is very unstable and even strange, which has always been a difficulty in potential field research.In view of the difficulty of magnetic anomaly polarity reduction in the low magnetic latitude, especially in the magnetic equator area, the concept of "narrow declination" is proposed by taking advantage of the stable transition from the vertical magnetization at the magnetic north pole to the horizontal magnetization direction in the low latitude area, and it is combined with the "inversion" interpretation method of the magnetic anomaly in the low latitude to propose a method specially used for polarity reduction at the magnetic equator. This method extends the existing theory of polarity reduction,The stabilized pole at the magnetic equator is realized, which is different from any other method. It is specially used for pole reduction calculation under (near) horizontal magnetization, and has the characteristics of simple principle, convenient implementation, fast convergence speed, etc.The calculation of theoretical model and actual data shows that this method of polar reduction for magnetic anomalies in the magnetic equator region is stable and reliable.[2]
Impact and correction
The magnetic compass is one of the important instruments for ship navigation. During PSC inspection, if it has defects or the deviation meter is not within the validity period, corrective measures of 17 (correction before sailing) or 30 (detention) will be given.Correcting the compass deviation during the sea voyage can make the course stable for more than 2 minutes or longer, and the crew can cooperate well without affecting the ship's voyage period. It can measure and eliminate the deviation more accurately and realistically, especially near the magnetic equator, because
(1) The ship's sway during navigation can be used to accurately correct the ship's tilt deviation;
(2) When the calibrator uses the Aili method for correction, the ship only rotates once in the correction water area. Due to the limitation of the water area, it brings many difficulties and inconvenience to ship manipulation and avoidance. In addition, relatively speaking, the ship is affected by the magnetic field near the port, which can be avoided in the sea far away from land;
(3) At and near the magnetic equator, due to the low geographical latitude, the wind and waves are relatively small, the ship is stable, can maintain a straight and flat state, and the influence of tilt deviation is minimal;
(4) At the magnetic equator, the north pointing force of the magnetic compass is the largest and the vertical force is the smallest.The small change of direction of the ship and the magnetic compass can respond in time, and the correction effect is good;
(5) At and near the magnetic equator, the geographical range is large, the room for rotation is large, the ship density is small, and the correction time is sufficient.[3]
