xenial (1) MagneticField.1.gz

Provided by: geographiclib-tools_1.45-2_amd64 bug

NAME

       MagneticField -- compute the earth's magnetic field

SYNOPSIS

       MagneticField [ -n name ] [ -d dir ] [ -t time | -c time lat h ] [ -r ] [ -w ] [ -T tguard ] [ -H hguard
       ] [ -p prec ] [ -v ] [ --comment-delimiter commentdelim ] [ --version | -h | --help ] [ --input-file
       infile | --input-string instring ] [ --line-separator linesep ] [ --output-file outfile ]

DESCRIPTION

       MagneticField reads in times and positions on standard input and prints out the geomagnetic field on
       standard output and, optionally, its rate of change.

       The input line is of the form time lat lon h. time is a date of the form 2012-07-03, a fractional year
       such as 2012.5, or the string "now".  lat and lon are the latitude and longitude expressed as decimal
       degrees or degrees, minutes, and seconds; for details on the allowed formats for latitude and longitude,
       see the "GEOGRAPHIC COORDINATES" section of GeoConvert(1).  h is the height above the ellipsoid in
       meters; this is optional and defaults to zero.  Alternatively, time can be given on the command line as
       the argument to the -t option, in which case it should not be included on the input lines.  Finally, the
       magnetic field can be computed at various points on a circle of latitude (constant time, lat, and h) via
       the -c option; in this case only the longitude should be given on the input lines.

       The output consists of the following 7 items:

         the declination (the direction of the horizontal component of
           the magnetic field measured clockwise from north) in degrees,
         the inclination (the direction of the magnetic field measured
           down from the horizontal) in degrees,
         the horizontal field in nanotesla (nT),
         the north component of the field in nT,
         the east component of the field in nT,
         the vertical component of the field in nT (down is positive),
         the total field in nT.

       If the -r option is given, a second line is printed giving the rates of change of these quantities in
       degrees/yr and nT/yr.

       The WGS84 ellipsoid is used, a = 6378137 m, f = 1/298.257223563.

OPTIONS

       -n  use magnetic field model name instead of the default "wmm2015".  See "MODELS".

       -d  read magnetic models from dir instead of the default.  See "MODELS".

       -t  evaluate the field at time instead of reading the time from the input lines.

       -c  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  on input and output, longitude precedes latitude (except that on input this can be overridden by a
           hemisphere designator, N, S, E, W).

       -T  signal an error if time lies tguard years (default 50 yr) beyond the range for the model.

       -H  signal an error if h lies hguard meters (default 500000 m) beyond the range for the model.

       -p  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
           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
           read input from the file infile instead of from standard input; a file name of "-" stands for
           standard input.

       --input-string
           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
           set the line separator character to linesep.  By default this is a semicolon.

       --output-file
           write output to the file outfile instead of to standard output; a file name of "-" stands for
           standard output.

MODELS

       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 earth's 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.sf.net/html/magnetic.html#magneticinst>.

ENVIRONMENT

       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.

ERRORS

       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.

EXAMPLES

       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.

SEE ALSO

       GeoConvert(1), geographiclib-get-magnetic(8).

AUTHOR

       MagneticField was written by Charles Karney.

HISTORY

       MagneticField was added to GeographicLib, <http://geographiclib.sf.net>, in version 1.15.