The model consists of a degree and order 12 spherical harmonic expansion of the magnetic scalar potential of the geomagnetic main field generated in the Earth's core.[2] Apart from the 168 spherical-harmonic "Gauss" coefficients, the model also has an equal number of spherical-harmonic secular variation coefficients predicting the temporal evolution of the field over the upcoming five-year epoch.
Updated model coefficients are released at 5-year intervals, with WMM2015 (released Dec 15, 2014) supposed to last until December 31, 2019. However, due to extraordinarily large and erratic movements of the north magnetic pole, an out-of-cycle update (WMM2015v2) was released in February 2019[4] (delayed by a few weeks due to the U.S. federal government shutdown)[5] to accurately model the magnetic field above 55° north latitude until the end of 2019. The next regular update (WMM2020) occurred in December 2019.[6]
The Enhanced Magnetic Model (EMM) is a sister product of the NGDC featuring a much higher amount of data to degree and order 790, giving a wavelength of 51 km as opposed to the 3000 km of WMM. At this resolution, it is not only able to model the Earth's magnetic field at the core-mantle boundary ("main field"), but also take into account magnetic anomalies caused by the minerals in the Earth's crust.[7]
^Witze, Alexandra (January 9, 2019). "Earth's magnetic field is acting up and geologists don't know why". Nature. 565 (7738): 143–144. Bibcode:2019Natur.565..143W. doi:10.1038/d41586-019-00007-1. PMID 30626958.
world, magnetic, model, large, spatial, scale, representation, earth, magnetic, field, developed, jointly, national, geophysical, data, center, british, geological, survey, data, updates, issued, national, geospatial, intelligence, agency, defence, geographic,. The World Magnetic Model WMM is a large spatial scale representation of the Earth s magnetic field It was developed jointly by the US National Geophysical Data Center and the British Geological Survey The data and updates are issued by the US National Geospatial Intelligence Agency and the UK Defence Geographic Centre 1 Magnetic declination map at sea level for the year 2010 derived from WMM2010 The model consists of a degree and order 12 spherical harmonic expansion of the magnetic scalar potential of the geomagnetic main field generated in the Earth s core 2 Apart from the 168 spherical harmonic Gauss coefficients the model also has an equal number of spherical harmonic secular variation coefficients predicting the temporal evolution of the field over the upcoming five year epoch WMM is the standard geomagnetic model of the United States Department of Defense DoD the Ministry of Defence United Kingdom the North Atlantic Treaty Organization NATO the World Hydrographic Office WHO navigation and attitude heading reference and the Federal Aviation Administration FAA It is also used widely in civilian navigation systems as the magnetic model of the World Geodetic System For example WMM is pre installed in Android and iOS devices to correct for the magnetic declination The WMM is produced by the U S National Geophysical Data Center NGDC in collaboration with the British Geological Survey BGS The model associated software and documentation are distributed by the NGDC on behalf of National Geospatial Intelligence Agency NGA 3 Updated model coefficients are released at 5 year intervals with WMM2015 released Dec 15 2014 supposed to last until December 31 2019 However due to extraordinarily large and erratic movements of the north magnetic pole an out of cycle update WMM2015v2 was released in February 2019 4 delayed by a few weeks due to the U S federal government shutdown 5 to accurately model the magnetic field above 55 north latitude until the end of 2019 The next regular update WMM2020 occurred in December 2019 6 Contents 1 Enhanced Magnetic Model EMM 2 See also 3 References 4 External linksEnhanced Magnetic Model EMM editThe Enhanced Magnetic Model EMM is a sister product of the NGDC featuring a much higher amount of data to degree and order 790 giving a wavelength of 51 km as opposed to the 3000 km of WMM At this resolution it is not only able to model the Earth s magnetic field at the core mantle boundary main field but also take into account magnetic anomalies caused by the minerals in the Earth s crust 7 See also editInternational Geomagnetic Reference Field another model of similar quality which models past years as well Runway numberingReferences edit David Bartlett Essentials of Positioning and Location Technology p 110 Cambridge University Press 2013 ISBN 1107354803 Chulliat Arnaud et al The US UK World Magnetic Model for 2015 2020 PDF ngdc noaa gov NOAA Airport Runway Names Shift with Magnetic Field National Centers for Environmental Information NCEI 16 November 2017 The World Magnetic Model and Associated Software National Centers for Environmental Information 4 February 2019 Retrieved 6 February 2019 Witze Alexandra January 9 2019 Earth s magnetic field is acting up and geologists don t know why Nature 565 7738 143 144 Bibcode 2019Natur 565 143W doi 10 1038 d41586 019 00007 1 PMID 30626958 World Magnetic Model NCEI National Centers for Environmental Information NCEI Enhanced Magnetic Model EMM www ngdc noaa gov External links editWMM model and software can be downloaded from the National Geophysical Data Center s WMM page World Magnetic Model method in the Android operating system World Magnetic Model 2015 NOAA press release nbsp This geophysics related article is a stub You can help Wikipedia by expanding it vte Retrieved from https en wikipedia org w index php title World Magnetic Model amp oldid 1182501497, wikipedia, wiki, book, books, library,
