Geofisica pura e applicata

, Volume 20, Issue 1, pp 31–45 | Cite as

Calculation of magnetic declination and horizontal intensity on the basis of the vertical intensity

  • Asger Lundbak


If the magnetic vertical intensityZ is known over a certain area, it is possible, under more precisely defined conditions which are often complied with, at arbitrary points of the same area—though with the exception of the marginal area—to calculate the deviations of the horizontal intensityH and the magnetic declinationD, ΔH and ΔD, from constant values. Below some details of the calculation in practice are given, i. a. by means of an example, the mathematic basis for the calculations being outlined in the introduction (the succeeding text may, however, be read independently thereof). A graticule, as seen in Fig. 1, was used in the calculations, and the method itself is described under «2. Procedure». In Figs. 2 and 3, the figures at the crosses denote the values ofH andD computed in this way, indicated in gammas and arc-minutes, respectively; (the isomagneticH-lines in Fig. 2 are drawn on the basis ofobserved H-values; in Fig. 3 the observedD0values themselves are given in figures in small type). The accuracy of and the possibilities for application of the method are discussed in the later sections.


Magnetic Declination Marginal Area Mathematic Basis Small Type Vertical Intensity 
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Wenn man die magnetische Vertikalintensität in einem Gebiet kennt, ist es unter gewissen Bedingungen, die oft erfüllt sind, möglich in willkürlich gewählten Punkten des Gebietes — mit Ausnahme des Randgebietes — die Abweichungen ΔH und ΔD der HorizontalintensitätH und der DeklinationD von konstanten Werten zu berechnen. Weiter unten sind Einzelheiten der praktischen Ausführung anhand eines Beispiels mitgeteilt. Die mathematische Grundlage der Berechnungen ist in der Einleitung skizziert; doch können die folgenden Abschnitte auch unabhängig von ihn verstanden werden. Für die Berechnungen wurde ein, Integrationsgitter (Abb. 1) verwendet, und die Methode selber ist unter «2. Procedure» beschrieben. In Abb. 2 und 3 zeigen die Zahlen bei den Kreuze die in dieser Weise berechneten Werte vonH undD, angegeben in Gammawerten und Bogenminuten; (die isomagnetischen Linien in Abb. 2 sind auf Grund vonbeobachteten H-Werten gezeichnet worden; in Abb. 3 sind die beobachtetenD-Werte in kleiner Typen gedruckt). In den Abschnitten 3 und 4 werden die Genauigkeit und die Anwendungsmöglichkeiten der Methode diskutiert.


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  1. Chapman, S.,Earth-Air Electric Currents and the Mutual Consistency of the Hand DIsomagnetic Charts. Terr. Mag., 47, 1–13 (1942).Google Scholar
  2. La Cour, D.,Le Quartz-Magnétomètre QHM. Publikationer fra det Danske Meteorologiske Institut, Communications Magnétiques, etc., N. 15 (1936).Google Scholar
  3. La Cour, D.,The Magnetometric Zero Balance, the BMZ. Publikationer fra Det Danske Metcorologiske Institut, Communications Magnétiques, etc., No. 19 (1942).Google Scholar
  4. Davids, N.,Calculation of Vertical Component Zfor Potential Fields from Observed Values of Declination Dand Horizontal Intensity H. Terr. Mag., 49, 239–242 (1944.,. se alsoVestine & Davids).Google Scholar
  5. Davids, N. &Bernstein, A.,On the Mutual Consistency of Magnetic Charts. Terr. Mag., 50, 199–214 (1945).Google Scholar
  6. Henderson, R. G. &Zietz, I.,The upward continuation of anomalies in total magnetic intensity fields. Geophysics, 14, 517–534 (1949, se alsoZietz & Henderson).CrossRefGoogle Scholar
  7. Hughes, D. S. &Pondrom, W. L.,Computation of Vertical Magnetic Anomalies from Total Magnetic Field Measurements. Trans. Amer. Geophys. Union, 28, 193–197 (1947).Google Scholar
  8. Logachev, A. A.,Magnetic surveys in airplane by the U.S.S.R., June 1936 [Abstract from «Information Book on Terrestrial Magnetism and Electricity, No. 3, Leningrad-Moscow, 1937», in Terr. Mag., 49, 214 (1944)].Google Scholar
  9. Lundbak, A.,Aeromagnetic Survey of Vertical Intensity over the Sound with Apparatus of the BMZ Type. Tellus, 3, 69–74 (1951).Google Scholar
  10. Malkin, N.,On the application of Neumann's problem to the investigation of magnetic fields at altitudes lying above the regions of anomalies [1935, abstracted in Geophysical Abstracts, 82, 1740 (1936)].Google Scholar
  11. Molin, K.,A general Earth magnetic investigation of Sweden. Part. 4: Vertical intensity and horizontal disturbing force. Sveriges geologiska Undersökning. Ser Ca. No. 34 (1942).Google Scholar
  12. Peters, L. J.,The Direct Approach to Magnetic Interpretation and Its Practical Application. Geophysics, 14, 290–320 (1949).CrossRefGoogle Scholar
  13. Rumbaugh, L. H. &Alldredge, L. R.,Airborne equipment for geomagnetic measurements. Trans. Amer. Geophys. Union, 30, 836–848 (1949).Google Scholar
  14. Schonstedt, E. O. & Irons, H. R.,Airborne Magnetometer for determining all Magnetic Components (Manuscript presented at the General Assembly of the International Union of Geodesy and Geophysics, Brussels, Belgium, August 21–September 1, 1951).Google Scholar
  15. Skeels, D. C. &Watson, R. J.,Derivation of Magnetic and Gravitational Quantities by Surface Integration. Geophysics, 14, 133–150 (1949).CrossRefGoogle Scholar
  16. Taylor, J. H.,On the Determination of Magnetic Vertical Intensity Z by Means of Surface Integrals. Terr. Mag., 49, 223–237 (1944).Google Scholar
  17. Vestine, E. H.,On the Analysis of Surface Magnetic Fields by Integrals, Part I. Terr. Mag., 46, 27–41 (1941).Google Scholar
  18. Vestine, E. H. &Davids, N.,Analysis and Interpretation of Geomagnetic Anomalies. Terr. Mag., 50, 1–36 (1945., see alsoDavids, N.).Google Scholar
  19. Zietz, I. &Henderson, R. G.,Magnetic Anomalies at High Altitudes. Trans. Amer. Geophys. Union, 32, 397–404 (1951, se alsoHenderson & Zietz).Google Scholar

Copyright information

© Istituto Geofisico Italiano 1951

Authors and Affiliations

  • Asger Lundbak
    • 1
  1. 1.Geophysicist at the Danish Meteorological InstituteCopenhagenDenmark

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