|-n name||use magnetic field model name instead of the default wmm2015. See MODELS.|
|-d dir||read magnetic models from dir instead of the default. See MODELS.|
|-t time||evaluate the field at time instead of reading the time from the input lines.|
|-c time lat h||evaluate the field on a circle of latitude given by time, lat, h instead of reading these quantities from the input lines. In this case, MagneticField can calculate the field considerably more quickly.|
|-r||toggle whether to report the rates of change of the field.|
|-w||toggle the longitude first flag (it starts off); if the flag is on, then on input and output, longitude precedes latitude (except that, on input, this can be overridden by a hemisphere designator, N, S, E, W).|
|-T tguard||signal an error if time lies tguard years (default 50 yr) beyond the range for the model.|
|-H hguard||signal an error if h lies hguard meters (default 500000 m) beyond the range for the model.|
|-p prec||set the output precision to prec (default 1). Fields are printed with precision with prec decimal places; angles use prec + 1 places.|
|-v||print information about the magnetic model on standard error before processing the input.|
|--comment-delimiter commentdelim||set the comment delimiter to commentdelim (e.g., # or //). If set, the input lines will be scanned for this delimiter and, if found, the delimiter and the rest of the line will be removed prior to processing and subsequently appended to the output line (separated by a space).|
|--version||print version and exit.|
|-h||print usage, the default magnetic path and name, and exit.|
|--help||print full documentation and exit.|
|--input-file infile||read input from the file infile instead of from standard input; a file name of - stands for standard input.|
|--input-string instring||read input from the string instring instead of from standard input. All occurrences of the line separator character (default is a semicolon) in instring are converted to newlines before the reading begins.|
|--line-separator linesep||set the line separator character to linesep. By default this is a semicolon.|
|--output-file outfile||write output to the file outfile instead of to standard output; a file name of - stands for standard output.|
MagneticField computes the geomagnetic field using one of the following models
wmm2010, the World Magnetic Model 2010, which approximates the main magnetic field for the period 2010-2015. See http://ngdc.noaa.gov/geomag/WMM/DoDWMM.shtml wmm2015, the World Magnetic Model 2015, which approximates the main magnetic field for the period 2015-2020. See http://ngdc.noaa.gov/geomag/WMM/DoDWMM.shtml igrf11, the International Geomagnetic Reference Field (11th generation), which approximates the main magnetic field for the period 1900-2015. See http://ngdc.noaa.gov/IAGA/vmod/igrf.html igrf12, the International Geomagnetic Reference Field (12th generation), which approximates the main magnetic field for the period 1900-2020. See http://ngdc.noaa.gov/IAGA/vmod/igrf.html emm2010, the Enhanced Magnetic Model 2010, which approximates the main and crustal magnetic fields for the period 2010-2015. See http://ngdc.noaa.gov/geomag/EMM/index.html emm2015, the Enhanced Magnetic Model 2015, which approximates the main and crustal magnetic fields for the period 2000-2020. See http://ngdc.noaa.gov/geomag/EMM/index.html
These models approximate the magnetic field due to the earths core and (in the case of emm2010) its crust. They neglect magnetic fields due to the ionosphere, the magnetosphere, nearby magnetized materials, electrical machinery, etc.
By default, the wmm2015 magnetic model is used. This may changed by setting the environment variable GEOGRAPHICLIB_MAGNETIC_NAME or with the -n option.
The magnetic models will be loaded from a directory specified at compile time. This may changed by setting the environment variables GEOGRAPHICLIB_MAGNETIC_PATH or GEOGRAPHICLIB_DATA, or with the -d option. The -h option prints the default magnetic path and name. Use the -v option to ascertain the full path name of the data file.
Instructions for downloading and installing magnetic models are available at <http://geographiclib.sourceforge.net/html/magnetic.html#magneticinst>.
GEOGRAPHICLIB_MAGNETIC_NAME Override the compile-time default magnetic name of wmm2015. The -h option reports the value of GEOGRAPHICLIB_MAGNETIC_NAME, if defined, otherwise it reports the compile-time value. If the -n name option is used, then name takes precedence. GEOGRAPHICLIB_MAGNETIC_PATH Override the compile-time default magnetic path. This is typically /usr/local/share/GeographicLib/magnetic on Unix-like systems and C:/ProgramData/GeographicLib/magnetic on Windows systems. The -h option reports the value of GEOGRAPHICLIB_MAGNETIC_PATH, if defined, otherwise it reports the compile-time value. If the -d dir option is used, then dir takes precedence. GEOGRAPHICLIB_DATA Another way of overriding the compile-time default magnetic path. If it is set (and if GEOGRAPHICLIB_MAGNETIC_PATH is not set), then $GEOGRAPHICLIB_DATA/magnetic is used.
An illegal line of input will print an error message to standard output beginning with ERROR: and causes MagneticField to return an exit code of 1. However, an error does not cause MagneticField to terminate; following lines will be converted. If time or h are outside the recommended ranges for the model (but inside the ranges increase by tguard and hguard), a warning is printed on standard error and the field (which may be inaccurate) is returned in the normal way.
The magnetic field from WMM2015 in Timbuktu on 2016-01-01
echo 2016-01-01 16:46:33N 3:00:34W 300 | MagneticField -r => -2.12 12.15 33871.9 33848.7 -1251.4 7293.9 34648.3 0.09 -0.08 31.8 33.8 53.7 -41.4 22.3
The first two numbers returned are the declination and inclination of the field. The second line gives the annual change.
MagneticField was written by Charles Karney.
MagneticField was added to GeographicLib, <http://geographiclib.sourceforge.net>, in version 1.15.
|GeographicLib 1.46||MAGNETICFIELD (1)||2016-02-14|