Magnetic reduction-to-the-pole at low latitudes: Observations and considerations

2008 ◽  
Vol 27 (8) ◽  
pp. 990-1002 ◽  
Author(s):  
Xiong Li
Keyword(s):  
Low Latitudes ◽  
Reduction To The Pole

Differential reduction to the pole: Revisited

Geophysics ◽  
2007 ◽  
Vol 72 (1) ◽  
pp. L13-L20 ◽  
Author(s):  
Jafar Arkani-Hamed
Keyword(s):  
Random Noise ◽  
Magnetic Anomalies ◽  
Space Domain ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Domain Reduction ◽  
Low Latitudes ◽  
Differential Reduction ◽  
Low Pass ◽  
Reduction To The Pole

Following a detailed investigation of the Fourier-domain differential reduction-to-the-pole (DRTP) algorithm I compared the results to those obtained using a space-domain reduction-to-the-pole algorithm. I demonstrate that DRTP reduces magnetic anomalies to the pole more effectively than the space-domain algorithm. The DRTP operator has singularities at the geomagnetic equator and enhances north-south trending features at low latitudes. The operator is modified by slightly increasing the inclination of the core field at low latitudes to suppress the singularity. This space-domain modification only affects the anomalies very close to the equator. The modified DRTP operator successfully reduces the magnetic anomalies at low latitudes to the pole. The effects of random noise added to the original magnetic anomalies are investigated in some detail, and an appropriate directional low-pass filter is used to remove the resulting enhanced noise in the reduced-to-the-pole magnetic anomalies. Very simple bodies (uniformly magnetized, cubic, or rectangular) are considered to clearly illustrate the effects of the DRTP, its modified version, and the directional low-pass filter.

NTRTP: A new reduction to the pole method at low latitudes via a nonlinear thresholding

2014 ◽  
Vol 111 ◽  
pp. 220-227 ◽  
Author(s):  
Henglei Zhang ◽  
Yára R. Marangoni ◽  
Xiangyun Hu ◽  
Renguang Zuo
Keyword(s):  
Low Latitudes ◽  
Reduction To The Pole

Reduction to the pole at low latitudes by Wiener filtering

Geophysics ◽  
1989 ◽  
Vol 54 (12) ◽  
pp. 1607-1613 ◽  
Author(s):  
R. O. Hansen ◽  
R. S. Pawlowski
Keyword(s):  
Frequency Domain ◽  
Synthetic Data ◽  
Wiener Filtering ◽  
Magnetic Data ◽  
Noise Power ◽  
Low Latitude ◽  
High Quality ◽  
Computational Load ◽  
Low Latitudes ◽  
Reduction To The Pole

Using simple estimates of the signal and noise power from gridded magnetic data, we design regulated frequency‐domain operators for reduction to the pole at low magnetic latitudes. These operators suppress the artifacts along the direction of the magnetic declination associated with the conventional reduction‐to‐the‐pole procedure, with negligible increase in computational load. The new procedure is applied to produce high‐quality reductions to the pole for noisy low‐latitude synthetic data and for magnetic data from the Dixon Seamount.

scholarly journals Enhancing the quality of interpretation magnetic data at low latitudes

2017 ◽  
Vol 1 (T4) ◽  
pp. 105-114
Author(s):  
Hai Hong Nguyen ◽  
Nhan Thanh Nhan ◽  
Liet Van Dang ◽  
Thu Ngoc Nguyen
Keyword(s):  
Magnetic Anomaly ◽  
Hilbert Transform ◽  
Amplitude Spectrum ◽  
Data Interpretation ◽  
Analytic Signal ◽  
Magnetic Data ◽  
Low Latitudes ◽  
Reduction To The Pole ◽  
Signal Method

Magnetic anomalies are antisymmetrical and often skewed to the location of the sources, because both of the magnetization and ambient field are not directed vertically, so it’s difficult to interpret. For reducing the magnetic anomaly to a symmetrical one – this located on the source of the anomaly – people often use the reduction to the pole (RTP) where the magnetization and ambient field are both directed vertically. However, at low latitudes (an absolute inclination less than 16o30’), the amplitude spectrum of the RTP’s operator was amplified at higher frequencies (short wavelengths) can form a narrow pie-shaped; so it produces artifacts elongated along the direction of the magnetic declination. Therefore, many methods of RTP at low latitudes are given to solve this problem, but most of them are not efficiency. In this paper, we performed enhancing the quality of interpretation of magnetic data at low latitudes by some RTP methods for magnetic data at low latitudes and the analytic signal method using gradient operator and Hilbert transform. This method is applied to a model and to a real magnetic anomaly to find out the best method. Then this method was applied to enhance the quality of magnetic data interpretation in the Southern Vietnam. The result showed that the analytic signal method using Hilbert transform allowed enhancing the quality of interpretatio of magnetic data n at low latitudes is the best.

Reduction to the pole at low latitudes by using the Taylor series iterative method

2018 ◽  
Vol 159 ◽  
pp. 127-134 ◽  
Author(s):  
Mengcheng Hao ◽  
Fengxu Zhang ◽  
Zhenhua Tai ◽  
Wei Du ◽  
Langning Ren ◽  
...  
Keyword(s):  
Iterative Method ◽  
Taylor Series ◽  
Low Latitudes ◽  
Reduction To The Pole

An improved technique for reduction to the pole at low latitudes

Geophysics ◽  
1996 ◽  
Vol 61 (1) ◽  
pp. 131-137 ◽  
Author(s):  
Pierre Keating ◽  
L. Zerbo
Keyword(s):  
Geomagnetic Latitude ◽  
Measured Data ◽  
Noise Model ◽  
Noise Power ◽  
Aeromagnetic Survey ◽  
Data Set ◽  
Low Latitudes ◽  
Reduction To The Pole ◽  
The Difference ◽  
Improved Technique

Reduction to the pole at low latitudes based on a Wiener filtering approach has been improved by introducing a deterministic noise model. It is assumed that the noise power is a fixed fraction of the signal power. This allows the method to be fully automated. Further improvement is obtained by requiring the reduced‐to‐the‐pole field to map into the observed field when projected to the geomagnetic latitude of the observed field. This is done by iteratively minimizing the difference between the measured field and the reduced‐to‐the‐pole field projected to the geomagnetic latitude of the measured data. This results in a reduced‐to‐the‐pole magnetic map that, when projected to the geomagnetic latitude of the given data, closely matches the measured data. The final reduced‐to‐the‐pole field does not show any of the artifacts typical of reduction‐to‐the‐pole at low geomagnetic latitudes. The method is demonstrated on a data set from an aeromagnetic survey flown over north‐central Burkina Faso, West Africa.

Sign in / Sign up

Export Citation Format

Share Document