World Magnetic Model

Calculate Earth's magnetic field at specific location and time using World Magnetic Model

Since R2019b

• 

×

Libraries:
Aerospace Blockset / Environment / Gravity

Description

The World Magnetic Model block implements the mathematical representation of the National Geospatial Intelligence Agency (NGA) World Magnetic Model. The World Magnetic Model block calculates the Earth magnetic field vector, horizontal intensity, declination, inclination, and total intensity at a specified location and time. The reference frame is north-east-down (NED).

Note

Use this block to model the Earth magnetic field between altitudes of -1,000 m to 850,000 m meters.

Limitations

All specifications have these limitations:

• The internal calculation of decimal year does not take into account local time or leap seconds.

• The specifications describe only the long-wavelength spatial magnetic fluctuations in the Earth's core. Intermediate and short-wavelength fluctuations, contributed from the crustal field (the mantle and crust), are not included. Also, the substantial fluctuations of the geomagnetic field, which occur constantly during magnetic storms and almost constantly in the disturbance field (auroral zones), are not included.

• This block has the limitations of the World Magnetic Model (WMM). WMM2020 is valid between -1km and 850km, as outlined in the World Magnetic Model 2020 Technical Report.

In addition, each specification has these limitations:

• WMM2015v2 supersedes WMM2015(v1). Consider replacing WMM2015(v1) with WMM2015v2 when used for navigation and other systems. WMM2015v2 was released by National Oceanic and Atmospheric Administration (NOAA) in February 2019 to correct performance degradation issues in the Arctic region for January 1, 2015, to December 31, 2019. Therefore, it is still acceptable to use WMM2015(v1) in systems below 55 degrees latitude in the Northern hemisphere.

• The WMM2020 specification produces data that is reliable five years after the epoch of the model, which is January 1, 2020.

• The WMM2015 specification produces data that is reliable five years after the epoch of the model, which is January 1, 2015.

• The WMM2010 specification produces data that is reliable five years after the epoch of the model, which is January 1, 2010.

• The WMM2005 specification produces data that is reliable five years after the epoch of the model, which is January 1, 2005.

• The WMM2000 specification produces data that is reliable five years after the epoch of the model, which is January 1, 2000.

Ports

Input

h — Height

scalar

Height, specified as a scalar, in selected units.

Data Types: double

μ (deg) — Latitude

scalar

Latitude, specified as a scalar, in degrees. If latitude is out of range, the block wraps it to be within the range when Action for out-of-range input is set to None or Warning. It does not wrap when Action for out-of-range is set to Error.

Data Types: double

l (deg) — Longitude

scalar

Longitude, specified as a scalar, in degrees. If longitude is out of range, the block wraps it to be within the range when Action for out-of-range input is set to None or Warning. It does not wrap when Action for out-of-range is set to Error.

Data Types: double

Decimal Year — Desired year

scalar

Desired year in a decimal format to include any fraction of the year that has already passed. The value is the current year plus the number of days that have passed in this year divided by 365.

For example, to calculate the decimal year, dyear, for March 21, 2015:

dyear=decyear('21-March-2015','dd-mmm-yyyy')

dyear =
   2.0152e+03

Data Types: double

Output

Magnetic Field (nT) — Magnetic field

vector

Magnetic field, returned as a vector, in selected units.

Data Types: double

Horizontal Intensity (nT) — Horizontal intensity

scalar

Horizontal intensity, returned as a scalar, in specified units.

Data Types: double

Declination (deg) — Declination

scalar

Declination, returned as a scalar, in degrees.

Data Types: double

Inclination (deg) — Inclination

scalar

Inclination, returned as a scalar, in degrees.

Data Types: double

Total Intensity (nT) — Total intensity

scalar

Total intensity, returned as a scalar, in selected units.

Data Types: double

Parameters

WMM coefficients — World Magnetic Model coefficient file

WMM2020 (2020-2025) (default) | WMM2015 V2 (2015-2020) | WMM2000 (2000-2005) | WMM2005 (2005-2010) | WMM2010 (2010-2015) | WMM2015 V1 (2015-2020) | Custom

World Magnetic Model coefficient file, selected from the list.

• WMM2000 (2000-2005) — World Magnetic Model 2000 coefficient file

• WMM2005 (2005-2010) — World Magnetic Model 2005 coefficient file

• WMM2010 (2010-2015) — World Magnetic Model 2010 coefficient file

• WMM2015 V1 (2015-2020) — World Magnetic Model 2015 (v1) coefficient file

• WMM2015 V2 (2015-2020) — World Magnetic Model 2015 (v2) coefficient file

• WMM2020 (2020-2025) — World Magnetic Model 2020 coefficient file

• Custom — Specify your own World Magnetic Model coefficient file. You can download a World Magnetic Model coefficient file from The World Magnetic Model.

Dependencies

Selecting Custom enables the Custom .COF file parameter.

Programmatic Use

Block Parameter: model

Type: character vector

Values: 'WMM2020 (2020-2025)' | 'WMM2015 V2 (2015-2020)' | 'WMM2000 (2000-2005)' | 'WMM2005 (2005-2010)' | 'WMM2010 (2010-2015)' | 'WMM2015 V1 (2015-2020)' | 'Custom'

Default: 'WMM2020 (2020-2025)'

Custom .COF file — Custom World Magnetic Model coefficient file

'WMM2020COF' (default) | any coefficient file name

World Magnetic Model coefficient file, downloaded from The World Magnetic Model. For example, if you want to download a coefficient file not yet listed in the WMM coefficients list.

Dependencies

To enable this parameter, select Custom for the WMM coefficients parameter.

Programmatic Use

Block Parameter: customFile

Type: character vector

Values: 'WMM2020.COF' | any coefficient file name

Default: 'WMM2020.COF'

Units — Input and output units

Metric (MKS) (default) | English

Input and output units:

Units	Height	Magnetic Field	Horizontal Intensity	Total Intensity
Metric (MKS)	Meters	Nanotesla	Nanotesla	Nanotesla
English	Feet	Nanogauss	Nanogauss	Nanogauss

Programmatic Use

Block Parameter: units

Type: character vector

Values: 'Metric (MKS)' | 'English'

Default: 'Metric (MKS)'

Input decimal year — Input decimal year

on (default) | off

• To specify the decimal year with an input port for the World Magnetic Model 2015 block, select this check box

• To specify the decimal year using the values of Month, Day, and Year, clear this check box.

Programmatic Use

Block Parameter: time_in

Type: character vector

Values: 'on' | 'off'

Default: 'on'

Month — Input month

January (default) | February | March | April | May | June | July | August | September | October | November | December

Month to calculate decimal year.

Dependencies

To enable this parameter, select Input decimal year.

Programmatic Use

Block Parameter: month

Type: character vector

Values: 'January' | 'February' | 'March' | 'April' | 'May' | 'June' | 'July' | 'August' | 'September' | 'October' | 'November' | 'December'

Default: 'January'

Day — Input day

1 (default) | 1 to 31

Day to calculate decimal year.

Dependencies

To enable this parameter, select Input decimal year.

Programmatic Use

Block Parameter: day

Type: character vector

Values: '1' to '31'

Default: '1'

Year — Input year

2020 (default) | any year

Year to calculate decimal year.

Dependencies

To enable this parameter, select Input decimal year.

Programmatic Use

Block Parameter: year

Type: character vector

Values: any year

Default: '2020'

Action for out-of-range input — Out-of-range action

Error (default) | Warning | None

Out-of-range block behavior, specified as follows.

Action	Description
None	No action.
Warning	Warning in the Diagnostic Viewer, model simulation continues.
Error (default)	Error in the Diagnostic Viewer, model simulation stops.

If longitude or latitude is out of range, the block wraps it to be within the range when Action for out-of-range input is set to None or Warning. It does not wrap when Action for out-of-range is set to Error.

The World Magnetic Model block accepts out-of-range height inputs (less than -1000 m or greater than 850000 m) when Action for out-of-range is set to None or Warning. However, the block output might not be accurate or reliable for these values. The World Magnetic Model is valid only between -1000 m and 850000 m.

Programmatic Use

Block Parameter: action

Type: character vector

Values: 'Error' | 'Warning' | 'None'

Default: 'Error'

Output horizontal intensity — Output horizontal intensity

on (default) | off

To output the horizontal intensity value, select this check box. Otherwise, clear this check box.

Dependencies

To enable the Horizontal Intensity output port, select this check box.

Programmatic Use

Block Parameter: h_out

Type: character vector

Values: 'on' | 'off'

Default: 'on'

Output declination — Output declination

on (default) | off

To output the declination, the angle between true north and the magnetic field vector (positive eastwards), select this check box. Otherwise, clear this check box.

Dependencies

To enable the Declination output port, select this check box.

Programmatic Use

Block Parameter: dec_out

Type: character vector

Values: 'on' | 'off'

Default: 'on'

Output inclination — Output inclination

on (default) | off

To output the inclination, the angle between the horizontal plane and the magnetic field vector (positive downwards), select this check box. Otherwise, clear this check box.

Dependencies

To enable the Inclination output port, select this check box.

Programmatic Use

Block Parameter: inc_out

Type: character vector

Values: 'on' | 'off'

Default: 'on'

Output total intensity — Output total intensity

on (default) | off

To output the total intensity, select this check box. Otherwise, clear this check box.

Dependencies

To enable the Total Intensity output port, select this check box.

Programmatic Use

Block Parameter: ti_out

Type: character vector

Values: 'on' | 'off'

Default: 'on'

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Version History

Introduced in R2019b