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int usage(int retval, bool brief) {
if (brief)
( retval ? std::cerr : std::cout ) << "Usage:\n"
" MagneticField [ -n name ] [ -d dir ] [ -t time | -c time lat h ] [ -r ]\n"
" [ -T tguard ] [ -H hguard ] [ -p prec ] [ -v ] [ --comment-delimiter\n"
" commentdelim ] [ --version | -h | --help ] [ --input-file infile |\n"
" --input-string instring ] [ --line-separator linesep ] [ --output-file\n"
" outfile ]\n"
"\n"
"For full documentation type:\n"
" MagneticField --help\n"
"or visit:\n"
" http://geographiclib.sf.net/1.37/MagneticField.1.html\n";
else
( retval ? std::cerr : std::cout ) << "Man page:\n"
"NAME\n"
" MagneticField -- compute the earth's magnetic field\n"
"\n"
"SYNOPSIS\n"
" MagneticField [ -n name ] [ -d dir ] [ -t time | -c time lat h ] [ -r ]\n"
" [ -T tguard ] [ -H hguard ] [ -p prec ] [ -v ] [ --comment-delimiter\n"
" commentdelim ] [ --version | -h | --help ] [ --input-file infile |\n"
" --input-string instring ] [ --line-separator linesep ] [ --output-file\n"
" outfile ]\n"
"\n"
"DESCRIPTION\n"
" MagneticField reads in times and positions on standard input and prints\n"
" out the geomagnetic field on standard output and, optionally, its rate\n"
" of change.\n"
"\n"
" The input line is of the form time lat lon h. time is a date of the\n"
" form 2012-07-03 or a fractional year such as 2012.5. lat and lon are\n"
" the latitude and longitude expressed as decimal degrees or degrees,\n"
" minutes, and seconds; see GeoConvert(1) for details. h is the height\n"
" above the ellipsoid in meters; this is optional and defaults to zero.\n"
" Alternatively, time can be given on the command line as the argument to\n"
" the -t option, in which case it should not be included on the input\n"
" lines. Finally, the magnetic field can be computed at various points\n"
" on a circle of latitude (constant time, lat, and h) via the -c option;\n"
" in this case only the longitude should be given on the input lines.\n"
"\n"
" The output consists of the following 7 items:\n"
"\n"
" the declination (the direction of the horizontal component of\n"
" the magnetic field measured clockwise from north) in degrees,\n"
" the inclination (the direction of the magnetic field measured\n"
" down from the horizontal) in degrees,\n"
" the horizontal field in nanotesla (nT),\n"
" the north component of the field in nT,\n"
" the east component of the field in nT,\n"
" the vertical component of the field in nT (down is positive),\n"
" the total field in nT.\n"
"\n"
" If the -r option is given, a second line is printed giving the rates of\n"
" change of these quantities in degrees/yr and nT/yr.\n"
"\n"
" The WGS84 ellipsoid is used, a = 6378137 m, f = 1/298.257223563.\n"
"\n"
"OPTIONS\n"
" -n use magnetic field model name instead of the default \"wmm2010\".\n"
" See \"MODELS\".\n"
"\n"
" -d read magnetic models from dir instead of the default. See\n"
" \"MODELS\".\n"
"\n"
" -t evaluate the field at time instead of reading the time from the\n"
" input lines.\n"
"\n"
" -c evaluate the field on a circle of latitude given by time, lat, h\n"
" instead of reading these quantities from the input lines. In this\n"
" case, MagneticField can calculate the field considerably more\n"
" quickly.\n"
"\n"
" -r toggle whether to report the rates of change of the field.\n"
"\n"
" -T signal an error if time lies tguard years (default 50 yr) beyond\n"
" the range for the model.\n"
"\n"
" -H signal an error if h lies hguard meters (default 500000 m) beyond\n"
" the range for the model.\n"
"\n"
" -p set the output precision to prec (default 1). Fields are printed\n"
" with precision with prec decimal places; angles use prec + 1\n"
" places.\n"
"\n"
" -v print information about the magnetic model on standard error before\n"
" processing the input.\n"
"\n"
" --comment-delimiter\n"
" set the comment delimiter to commentdelim (e.g., \"#\" or \"//\"). If\n"
" set, the input lines will be scanned for this delimiter and, if\n"
" found, the delimiter and the rest of the line will be removed prior\n"
" to processing and subsequently appended to the output line\n"
" (separated by a space).\n"
"\n"
" --version\n"
" print version and exit.\n"
"\n"
" -h print usage, the default magnetic path and name, and exit.\n"
"\n"
" --help\n"
" print full documentation and exit.\n"
"\n"
" --input-file\n"
" read input from the file infile instead of from standard input; a\n"
" file name of \"-\" stands for standard input.\n"
"\n"
" --input-string\n"
" read input from the string instring instead of from standard input.\n"
" All occurrences of the line separator character (default is a\n"
" semicolon) in instring are converted to newlines before the reading\n"
" begins.\n"
"\n"
" --line-separator\n"
" set the line separator character to linesep. By default this is a\n"
" semicolon.\n"
"\n"
" --output-file\n"
" write output to the file outfile instead of to standard output; a\n"
" file name of \"-\" stands for standard output.\n"
"\n"
"MODELS\n"
" MagneticField computes the geomagnetic field using one of the following\n"
" models\n"
"\n"
" wmm2010, the World Magnetic Model 2010, which approximates the\n"
" main magnetic field for the period 2010-2015. See\n"
" http://ngdc.noaa.gov/geomag/WMM/DoDWMM.shtml\n"
" igrf11, the International Geomagnetic Reference Field (11th\n"
" generation) which approximates the main magnetic field for\n"
" the period 1900-2015. See\n"
" http://ngdc.noaa.gov/IAGA/vmod/igrf.html\n"
" emm2010, the Enhanced Magnetic Model 2010, which approximates the\n"
" main and crustal magnetic fields for the period 2010-2015. See\n"
" http://ngdc.noaa.gov/geomag/EMM/index.html\n"
"\n"
" These models approximate the magnetic field due to the earth's core and\n"
" (in the case of emm2010) its crust. They neglect magnetic fields due\n"
" to the ionosphere, the magnetosphere, nearby magnetized materials,\n"
" electrical machinery, etc.\n"
"\n"
" By default, the \"wmm2010\" magnetic model is used. This may changed by\n"
" setting the environment variable \"GEOGRAPHICLIB_MAGNETIC_NAME\" or with\n"
" the -n option.\n"
"\n"
" The magnetic models will be loaded from a directory specified at\n"
" compile time. This may changed by setting the environment variables\n"
" \"GEOGRAPHICLIB_MAGNETIC_PATH\" or \"GEOGRAPHICLIB_DATA\", or with the -d\n"
" option. The -h option prints the default magnetic path and name. Use\n"
" the -v option to ascertain the full path name of the data file.\n"
"\n"
" Instructions for downloading and installing magnetic models are\n"
" available at\n"
" <http://geographiclib.sf.net/html/magnetic.html#magneticinst>.\n"
"\n"
"ENVIRONMENT\n"
" GEOGRAPHICLIB_MAGNETIC_NAME\n"
" Override the compile-time default magnetic name of \"wmm2010\". The\n"
" -h option reports the value of GEOGRAPHICLIB_MAGNETIC_NAME, if\n"
" defined, otherwise it reports the compile-time value. If the -n\n"
" name option is used, then name takes precedence.\n"
"\n"
" GEOGRAPHICLIB_MAGNETIC_PATH\n"
" Override the compile-time default magnetic path. This is typically\n"
" \"/usr/local/share/GeographicLib/magnetic\" on Unix-like systems and\n"
" \"C:/ProgramData/GeographicLib/magnetic\" on Windows systems. The -h\n"
" option reports the value of GEOGRAPHICLIB_MAGNETIC_PATH, if\n"
" defined, otherwise it reports the compile-time value. If the -d\n"
" dir option is used, then dir takes precedence.\n"
"\n"
" GEOGRAPHICLIB_DATA\n"
" Another way of overriding the compile-time default magnetic path.\n"
" If it is set (and if GEOGRAPHICLIB_MAGNETIC_PATH is not set), then\n"
" $GEOGRAPHICLIB_DATA/magnetic is used.\n"
"\n"
"ERRORS\n"
" An illegal line of input will print an error message to standard output\n"
" beginning with \"ERROR:\" and causes MagneticField to return an exit code\n"
" of 1. However, an error does not cause MagneticField to terminate;\n"
" following lines will be converted. If time or h are outside the\n"
" recommended ranges for the model (but inside the ranges increase by\n"
" tguard and hguard), a warning is printed on standard error and the\n"
" field (which may be inaccurate) is returned in the normal way.\n"
"\n"
"EXAMPLES\n"
" The magnetic field from WMM2010 in Timbuktu on 2012-01-01\n"
"\n"
" echo 2012-01-01 16:46:33N 3:00:34W 300 | MagneticField -r\n"
" => -2.55 12.43 33771.0 33737.6 -1500.5 7446.0 34582.1\n"
" 0.10 -0.07 34.3 36.8 54.4 -35.3 25.9\n"
"\n"
" The first two numbers returned are the declination and inclination of\n"
" the field. The second line gives the annual change.\n"
"\n"
"SEE ALSO\n"
" GeoConvert(1).\n"
"\n"
"AUTHOR\n"
" MagneticField was written by Charles Karney.\n"
"\n"
"HISTORY\n"
" MagneticField was added to GeographicLib,\n"
" <http://geographiclib.sf.net>, in version 1.15.\n"
;
return retval;
}
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