Earth’s magnetic declination was experimentally measured at 15 sites in western USA from Alaska to Texas;each site exhibited a large linear feature identifiable in virtual globe imagery(NASA’s World Wind or Google E...Earth’s magnetic declination was experimentally measured at 15 sites in western USA from Alaska to Texas;each site exhibited a large linear feature identifiable in virtual globe imagery(NASA’s World Wind or Google Earth).The difference between the geographic bearing of the linear feature measured directly on a virtual globe image and the magnetic bearing of the same linear feature measured on the ground with a compass defines the magnetic declination d for that site.For all 15 sites,d values,determined by this differencing procedure,ranged from about 208 to 58 E and fell within 18(over half within 0.58)of expected values.Global positioning system(GPS)data recorded at most sites and plotted on virtual globe images aided in the identification of relevant features.This straightforward method for determining magnetic declination using virtual globe software and a compass provides a contemporary geospatial field/laboratory activity that dramatically elucidates and contrasts features of magnetic and geographic coordinate systems for students in various disciplines involving geomagnetism,navigation,geography or spherical polar geometry.展开更多
The Earth’s magnetic declination,a key parameter of the geomagnetic field,has long provided a fundamental reference for navigation,orientation,and geospatial positioning.Owing to temporal and spatial variations in th...The Earth’s magnetic declination,a key parameter of the geomagnetic field,has long provided a fundamental reference for navigation,orientation,and geospatial positioning.Owing to temporal and spatial variations in the geomagnetic field,periodic model updates are essential for maintaining positional accuracy and geophysical consistency.This study modelled the spatiotemporal variability of magnetic declination across Nigeria over 15 years(2010-2025)to enhance geomagnetic referencing for sustainable navigation and mapping systems.The study employed a quantitative geoscientific methodology.The study integrated International Geomagnetic Reference Field(IGRF-14)Gauss coefficients using MATLAB programming to compute magnetic field elements and generate declination models at a 1:50,000 scale.Analytical outputs revealed significant regional variations,with the North-West,South-South,and South-East zones recording the highest declination changes of 2.40˚,2.10˚,and 2.00˚,respectively.Conversely,the North-Central,North-East,and South-West zones exhibited relatively lower variations of 0.70˚,1.20˚,and 1.70˚,respectively.A comparative assessment between declination values from the developed model and those derived from the global geomagnetic calculator revealed minimal discrepancies(−0.009480 to−0.001340),with root mean square errors ranging from 0.00470 to 0.00670.These findings underscore the importance of the magnitude of secular variations of magnetic declination across Nigeria.The variability of these values provides a veritable basis to support geospatial infrastructure development,accurate navigation,and calibration of inertial systems.Regular updates of isogonic maps and geomagnetic parameters are therefore recommended to strengthen national geospatial frameworks,enhance disaster preparedness,and promote SDG-aligned geoscience innovations that underpin resilient infrastructure and sustainable urban development.展开更多
It is possible to conclude that typical course of graph which analyse course of germinability during the year at every cultivar is observable. Germination usually shows a minimum in December, but mainly in January and...It is possible to conclude that typical course of graph which analyse course of germinability during the year at every cultivar is observable. Germination usually shows a minimum in December, but mainly in January and in February. Maximum of germinability is observed in the spring and summer time. This phenomenon isn’t result of the dormancy or secondary dormancy because during of long term seed storage, germinability has similar curve every year, only number of germinative seeds stepwise decrease every year at every month of storage. Every species or cultivar of crops has a typical course of the germinability during the year. There are also species (crops), that have germination process during the year almost constant i.e., without variation during the year, but it is a minority of genotypes, rather exceptions. The annual course of germination is nearly identical to the annual course of the magnetic declination. From the theoretical practical view, there is possibility (but not certainty!) that in case of testing the seed germination at begin or end of year at genotypes with large variability of germinability during the year, that this phenomenon have negative impact on seed certification by companies producing seeds for cultivation practice in some species.展开更多
Howarth provides a deep view of the history of those geophysical sciences of the 19th and 20th centuries bordering most closely on geology,a task for which he is well qualified.He studied geology in the 1960s,he taugh...Howarth provides a deep view of the history of those geophysical sciences of the 19th and 20th centuries bordering most closely on geology,a task for which he is well qualified.He studied geology in the 1960s,he taught the application of statistics to geology for thirty years,and he has published broadly on mathematical geology.In a series of journal articles he has also used this expertise to examine the often unexplained quantitative methods used to map Earth’s magnetic declination in the 18^(th)century.He also applied his extensive background in graphical methods in the geosciences to the history of mineralogy and petrology.In short,Dr.Howarth is a geologist with historical sensibilities and an eye for the roles of mathematics and physics in geological development.This important book culminates decades of historical research.展开更多
The Mesoproterozoic mafic dyke swarms are extensively distributedin the central North China Craton(NCC) including North Shanxi, Wutai and Lüliang areas, which are not deformed and metamorphic but high magnetic, s...The Mesoproterozoic mafic dyke swarms are extensively distributedin the central North China Craton(NCC) including North Shanxi, Wutai and Lüliang areas, which are not deformed and metamorphic but high magnetic, so the dyke swarms become the mark to compare the high meta-morphic rock areas in magnetism. Based on the analysis of paleomagnetism of mafic dyke swarms in North Shanxi, Wutai and Lüliang areas, NCC inclined southward about 18° so that North Shanxi lifted up and rotated 10° left to Wutai area. The dyke swarms in Lüliang developed later than in North Shanxi and Wutai area. The NNW-trending and WNW-trending dyke swarms developed in Lüliang while the North China Plate moved northward consistently so that the paleomagnetism of dyke swarms in Lüliang is greatly different from North Shanxi and Wutai area.展开更多
文摘Earth’s magnetic declination was experimentally measured at 15 sites in western USA from Alaska to Texas;each site exhibited a large linear feature identifiable in virtual globe imagery(NASA’s World Wind or Google Earth).The difference between the geographic bearing of the linear feature measured directly on a virtual globe image and the magnetic bearing of the same linear feature measured on the ground with a compass defines the magnetic declination d for that site.For all 15 sites,d values,determined by this differencing procedure,ranged from about 208 to 58 E and fell within 18(over half within 0.58)of expected values.Global positioning system(GPS)data recorded at most sites and plotted on virtual globe images aided in the identification of relevant features.This straightforward method for determining magnetic declination using virtual globe software and a compass provides a contemporary geospatial field/laboratory activity that dramatically elucidates and contrasts features of magnetic and geographic coordinate systems for students in various disciplines involving geomagnetism,navigation,geography or spherical polar geometry.
文摘The Earth’s magnetic declination,a key parameter of the geomagnetic field,has long provided a fundamental reference for navigation,orientation,and geospatial positioning.Owing to temporal and spatial variations in the geomagnetic field,periodic model updates are essential for maintaining positional accuracy and geophysical consistency.This study modelled the spatiotemporal variability of magnetic declination across Nigeria over 15 years(2010-2025)to enhance geomagnetic referencing for sustainable navigation and mapping systems.The study employed a quantitative geoscientific methodology.The study integrated International Geomagnetic Reference Field(IGRF-14)Gauss coefficients using MATLAB programming to compute magnetic field elements and generate declination models at a 1:50,000 scale.Analytical outputs revealed significant regional variations,with the North-West,South-South,and South-East zones recording the highest declination changes of 2.40˚,2.10˚,and 2.00˚,respectively.Conversely,the North-Central,North-East,and South-West zones exhibited relatively lower variations of 0.70˚,1.20˚,and 1.70˚,respectively.A comparative assessment between declination values from the developed model and those derived from the global geomagnetic calculator revealed minimal discrepancies(−0.009480 to−0.001340),with root mean square errors ranging from 0.00470 to 0.00670.These findings underscore the importance of the magnitude of secular variations of magnetic declination across Nigeria.The variability of these values provides a veritable basis to support geospatial infrastructure development,accurate navigation,and calibration of inertial systems.Regular updates of isogonic maps and geomagnetic parameters are therefore recommended to strengthen national geospatial frameworks,enhance disaster preparedness,and promote SDG-aligned geoscience innovations that underpin resilient infrastructure and sustainable urban development.
文摘It is possible to conclude that typical course of graph which analyse course of germinability during the year at every cultivar is observable. Germination usually shows a minimum in December, but mainly in January and in February. Maximum of germinability is observed in the spring and summer time. This phenomenon isn’t result of the dormancy or secondary dormancy because during of long term seed storage, germinability has similar curve every year, only number of germinative seeds stepwise decrease every year at every month of storage. Every species or cultivar of crops has a typical course of the germinability during the year. There are also species (crops), that have germination process during the year almost constant i.e., without variation during the year, but it is a minority of genotypes, rather exceptions. The annual course of germination is nearly identical to the annual course of the magnetic declination. From the theoretical practical view, there is possibility (but not certainty!) that in case of testing the seed germination at begin or end of year at genotypes with large variability of germinability during the year, that this phenomenon have negative impact on seed certification by companies producing seeds for cultivation practice in some species.
文摘Howarth provides a deep view of the history of those geophysical sciences of the 19th and 20th centuries bordering most closely on geology,a task for which he is well qualified.He studied geology in the 1960s,he taught the application of statistics to geology for thirty years,and he has published broadly on mathematical geology.In a series of journal articles he has also used this expertise to examine the often unexplained quantitative methods used to map Earth’s magnetic declination in the 18^(th)century.He also applied his extensive background in graphical methods in the geosciences to the history of mineralogy and petrology.In short,Dr.Howarth is a geologist with historical sensibilities and an eye for the roles of mathematics and physics in geological development.This important book culminates decades of historical research.
基金the National Natural Science Foundation of China (Grant No. 49832030).
文摘The Mesoproterozoic mafic dyke swarms are extensively distributedin the central North China Craton(NCC) including North Shanxi, Wutai and Lüliang areas, which are not deformed and metamorphic but high magnetic, so the dyke swarms become the mark to compare the high meta-morphic rock areas in magnetism. Based on the analysis of paleomagnetism of mafic dyke swarms in North Shanxi, Wutai and Lüliang areas, NCC inclined southward about 18° so that North Shanxi lifted up and rotated 10° left to Wutai area. The dyke swarms in Lüliang developed later than in North Shanxi and Wutai area. The NNW-trending and WNW-trending dyke swarms developed in Lüliang while the North China Plate moved northward consistently so that the paleomagnetism of dyke swarms in Lüliang is greatly different from North Shanxi and Wutai area.
