Use the tool below to compute values for the geomagnetic field and secular variation for a given set of coordinates and date. This calculator uses the World Magnetic Model as released in Dec 2024.
Choose the geodetic/geocentric latitude and longitude either by entering the coordinates into the form below
(decimal degrees may be entered into the 'degrees' field, and degrees S or W should be entered with a negative sign), or by simply clicking the location
on the map. The altitude or radius and date may be set using the appropriate form fields.
Clicking on the 'Show result on map' button will display the values for the chosen coordinates
in a pop-up window. These results may be saved by clicking on the 'Save' button allowing you to
compare values from a number of locations.
Coordinate Filters
Geocentric: Allows for input as latitude/longitude/radius, where radius is the distance from the centre of the Earth. Radius must be greater than 3471km (i.e. not inside the Earth's core).
Geodetic: Allows for input as latitude/longitude/altitude, where altitude is km above mean sea level. Altitude must be greater than -2300km (i.e. not inside the Earth's core).
Specify latitude and longitude as one of:
Examples
Description
40°44'55"N
40:44:55S
73 59 11W
Degrees, minutes and seconds suffixed with 'N'/'S' (for latitude) or 'E'/'W' (for longitude)
to indicate the hemisphere.
Degree, minute, and second values can be separated either by the
standard symbols for angles (°, ' and ") or by colon characters (:) or by spaces.
Negative numbers may not be used.
Degree, minute and second values must all be integers - no decimal values are allowed
40.7486
-40.7486
-73.9864
Signed decimal degrees without compass direction ('N'/'S' or 'E'/'W'). Negative
values indicate south latitude or west longitude.
Temporal Filter
Date: must be between 2024-01-01 and 2034-12-31
Decimal year: can be greater or equal to 2025 and less than 2035.
Inputs beyond 2030 are not recommended as accuracy will be reduced.
Model Resolution
Standard [World Magnetic Model]
The internal time-varying field to spherical harmonic degree 12, or about 3200km at the equator
High Resolution [World Magnetic Model - High Resolution]:
The internal time-varying field to degree 15, and a static crustal field from degree 16 to degree 133, or about 300km at the equator
Warning: One or more input values are invalid!
Caution:Dates beyond 2030 are not recommended! Inputs of 2035 onwards do not work.
Warning: Saved results cannot exceed 50. Please clear your saved outputs and try again.
Legend
Model result parameters are described in the table below.
MF = Main Field
SV = Secular Variation
D = Declination
degrees east
arcmin/year
I = Inclination
degrees down
arcmin/year
X = North Intensity
nT
nT/year
Y = East Intensity
nT
nT/year
H = Horizontal Intensity
nT
nT/year
Z = Vertical Intensity
nT down
nT/year
F = Total Intensity
nT
nT/year
As this is based on a web service you can also obtain results in XML/JSON format using an HTTP GET request. Fetch data in XML format
here modifying the query string parameters as appropriate.
Learn More
The Earth's magnetic field is a vector quantity; at each point in space it has a strength and a direction. To completely describe it we need three quantities. These may be:
X, Y, and Z - three orthogonal strength components
F, D, and I - the total field strength and two angles
H, Z, and D - two strength components and an angle
The relationship between these 7 elements can be viewed at: INTERMAGNET
Secular variation (SV) is typically defined as the slow annual to decadal change of the Eath's magnetic field and is caused by the flow of liquid in the outer core,
deep inside the Earth. The change of the field is not easily predictable due to the nature of the flow regime in the core and the mechanism by which the magnetic field is generated.
However, an estimate of the instantaneous flow itself can be computed, if we make some assumptions about its nature and how it affects the magnetic field we observe at the surface.
If we have a longer series of data we can compute the accelerated flow too.
