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<title>MGD77MAGREF</title>
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<h1 align="center">MGD77MAGREF</h1>
<a href="#NAME">NAME</a><br>
<a href="#SYNOPSIS">SYNOPSIS</a><br>
<a href="#DESCRIPTION">DESCRIPTION</a><br>
<a href="#OPTIONS">OPTIONS</a><br>
<a href="#TIME SETTINGS">TIME SETTINGS</a><br>
<a href="#EXAMPLES">EXAMPLES</a><br>
<a href="#SEE ALSO">SEE ALSO</a><br>
<a href="#REFERENCES">REFERENCES</a><br>
<hr>
<h2>NAME
<a name="NAME"></a>
</h2>
<p style="margin-left:11%; margin-top: 1em">mgd77magref
− Evaluate the IGRF or CM4 magnetic field models</p>
<h2>SYNOPSIS
<a name="SYNOPSIS"></a>
</h2>
<p style="margin-left:11%; margin-top: 1em"><b>mgd77magref</b>
[ <i>inputfile</i> ] [
<b>−A</b>[<b>+a</b><i>alt</i><b>+t</b><i>date</i><b>+y</b>]
] [ <b>−C</b><i>cm4file</i> ] [
<b>−D</b><i>Dstfile</i> ] [
<b>−E</b><i>f107file</i> ] [
<b>−F</b><i>flags</i> ] [ <b>−G</b> ] [
<b>−H</b>[<b>i</b>][<i>nrec</i>] ] [
<b>−Sc</b>|<b>l</b><i>low/high</i> ] [ <b>−V</b>
] [ <b>−:</b>[<b>i</b>|<b>o</b>] ] [
<b>−b</b>[<b>i</b>|<b>o</b>][<b>s</b>|<b>S</b>|<b>d</b>|<b>D</b>[<i>ncol</i>]|<b>c</b>[<i>var1</i><b>/</b><i>...</i>]]
] [ <b>−f</b>[<b>i</b>|<b>o</b>]<i>colinfo</i> ] [
<b>−m</b>[<b>i</b>|<b>o</b>][<i>flag</i>] ]</p>
<h2>DESCRIPTION
<a name="DESCRIPTION"></a>
</h2>
<p style="margin-left:11%; margin-top: 1em"><b>mgd77magref</b>
will evaluate the IGRF or the CM4 geomagnetic models at the
specified locations and times.</p>
<h2>OPTIONS
<a name="OPTIONS"></a>
</h2>
<p style="margin-left:11%; margin-top: 1em">No space
between the option flag and the associated arguments.
<i><br>
inputfile</i></p>
<p style="margin-left:22%;">Contains the moments in
space-time where we want to evaluate the magnetic reference
field. The first two columns must contain longitude and
latitude (however, see <b>−:</b> for latitude and
longitude instead). Normally, the third and fourth columns
must contain altitude (in km) and time, respectively, but if
one or both of these are constant for all records they can
be supplied via the <b>−A</b> option instead and are
thus not expected in the input file. If no input file is
given we read <i>stdin</i>. A note about the CM4 validity
domain. The core field of CM4 is valid from 1960-2002.5 but
the ionospheric and magnetospheric fields are computed after
the <i>Dst</i> and <i>F10.7</i> coefficient files. We
extended here those coefficient files up to 2007, which
means that one can compute external contributions up until
2007 but the Secular Variation will be biased (non
reliable). New indices files may be retrieved
from:ftp://ftp.ngdc.noaa.gov/STP/GEOMAGNETIC_DATA/INDICES/DST/
(the <i>Dst</i> coefficients) and
ftp://ftp.ngdc.noaa.gov/STP/SOLAR_DATA/SOLAR_RADIO/FLUX/
(The <i>F10.7</i> index file is a MONTHPLT.ABS). NOTE: since
the <i>Dst</i> files in the .../DST/ directory are still
only up to 2007, for GMT4.5.3 we extended the <i>Dst</i>
until April 2010 by reformatting the data in the preliminary
file Est_Ist_index_0_mean.pli, which is at
ftp://ftp.ngdc.noaa.gov/STP/GEOMAGNETIC_DATA/INDICES/EST_IST/</p>
<table width="100%" border="0" rules="none" frame="void"
cellspacing="0" cellpadding="0">
<tr valign="top" align="left">
<td width="11%"></td>
<td width="3%">
<p><b>−A</b></p></td>
<td width="8%"></td>
<td width="78%">
<p>Adjusts how the input record is interpreted. Append
<b>+a</b> to set a fixed <i>altitude</i> (in km) that should
apply to all data records [Default expects <i>altitude</i>
to be in the 3rd column of all records]. Append <b>+t</b> to
set a fixed <i>time</i> that should apply to all data
records [Default expects <i>time</i> to be in the 4th column
of all records]. Finally, append <b>+y</b> to indicate that
all times are specified as decimal years [Default is ISO
<i>date</i>T<i>colck</i> format].</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="3%">
<p><b>−C</b></p></td>
<td width="8%"></td>
<td width="78%">
<p>Specify an alternate CM4 coefficient file
[umdl.CM4].</p> </td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="3%">
<p><b>−D</b></p></td>
<td width="8%"></td>
<td width="78%">
<p>Specify an alternate file with hourly means of the Dst
index for CM4 [Dst_all.wdc]. Alternatively, simply specify a
single index to apply for all records.</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="3%">
<p><b>−E</b></p></td>
<td width="8%"></td>
<td width="78%">
<p>Specify an alternate file with monthly means of absolute
F10.7 solar radio flux for CM4 [F107_mon.plt].
Alternatively, simply specify a single flux to apply for all
records.</p> </td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="3%">
<p><b>−F</b></p></td>
<td width="8%"></td>
<td width="78%">
<p>Selects output items; <i>flags</i> is a string made up
of one or more of these characters:</p></td></tr>
</table>
<p style="margin-left:22%;"><b>r</b> means output all input
columns before adding the items below <b><br>
t</b> means list total field (nT). <b><br>
h</b> means list horizontal field (nT). <b><br>
x</b> means list X component (nT, positive north). <b><br>
y</b> means list Y component (nT, positive east). <b><br>
z</b> means list Z component (nT, positive down). <b><br>
d</b> means list declination (deg, clockwise from north).
<b><br>
i</b> means list inclination (deg, positive down). <br>
Append one or more number to indicate the requested field
contribution(s): <b><br>
0</b> means IGRF field (no combinations allowed) <b><br>
1</b> means CM4 Core field <b><br>
2</b> means CM4 Lithospheric field <b><br>
3</b> means CM4 Primary Magnetospheric field <b><br>
4</b> means CM4 Induced Magnetospheric field <b><br>
5</b> means CM4 Primary ionospheric field <b><br>
6</b> means CM4 Induced ionospheric field <b><br>
7</b> means CM4 Toroidal field <b><br>
9</b> means Core field from IGRF and other contributions
from CM4. DO NOT USE BOTH 1 AND 9. <br>
Appending several numbers (1-7) will add up the different
contributions. For example <b>−Ft</b>/<b>12</b>
computes the total field due to Core and Lithospheric
sources. Two special cases are allowed, which mix which Core
field from IGRF and other sources from CM4.
<b>−Ft</b>/<b>934</b> computes Core field due to IGRF
plus terms 3 and 4 from CM4 (but you can add others).
<b>−Ft</b>/<b>934</b> the same as above but output the
field components. The data is written out in the order they
appear in <i>flags</i> [Default is
<b>−Frthxyzdi</b>/<b>1</b>].</p>
<table width="100%" border="0" rules="none" frame="void"
cellspacing="0" cellpadding="0">
<tr valign="top" align="left">
<td width="11%"></td>
<td width="3%">
<p style="margin-top: 1em"><b>−G</b></p></td>
<td width="8%"></td>
<td width="78%">
<p style="margin-top: 1em">Specifies that coordinates are
geocentric [geodetic].</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="3%">
<p><b>−H</b></p></td>
<td width="8%"></td>
<td width="78%">
<p>Input file(s) has header record(s). If used, the default
number of header records is <b><A HREF="gmtdefaults.html#N_HEADER_RECS">N_HEADER_RECS</A></b>. Use
<b>−Hi</b> if only input data should have header
records [Default will write out header records if the input
data have them]. Blank lines and lines starting with # are
always skipped.</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="3%">
<p><b>−L</b></p></td>
<td width="8%"></td>
<td width="78%">
<p>Computes J field vectors from certain external
sources.</p> </td></tr>
</table>
<p style="margin-left:22%;"><b>r</b> means output all input
columns before adding the items below (all in Ampers/m).
<b><br>
t</b> means list magnitude field. <b><br>
x</b> means list X component. <b><br>
y</b> means list Y component. <b><br>
z</b> means list Z or current function Psi. <br>
Append a number to indicate the requested J contribution:
<b><br>
1</b> means Induced Magnetospheric field. <b><br>
2</b> means Primary ionospheric field. <b><br>
3</b> means Induced ionospheric field. <b><br>
4</b> means Poloidal field.</p>
<table width="100%" border="0" rules="none" frame="void"
cellspacing="0" cellpadding="0">
<tr valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p style="margin-top: 1em"><b>−Sc</b></p></td>
<td width="7%"></td>
<td width="78%">
<p style="margin-top: 1em">Limits the wavelengths of the
core field contribution to the band indicated by the low and
high spherical harmonic order [1/13].</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p><b>−Sl</b></p></td>
<td width="7%"></td>
<td width="78%">
<p>Limits the wavelengths of the lithosphere field
contribution to the band indicated by the low and high
spherical harmonic order [14/65].</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p><b>−V</b></p></td>
<td width="7%"></td>
<td width="78%">
<p>Selects verbose mode, which will send progress reports
to stderr [Default runs "silently"].</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p><b>−:</b></p></td>
<td width="7%"></td>
<td width="78%">
<p>Toggles between (longitude,latitude) and
(latitude,longitude) input and/or output. [Default is
(longitude,latitude)]. Append <b>i</b> to select input only
or <b>o</b> to select output only. [Default affects
both].</p> </td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p><b>−bi</b></p></td>
<td width="7%"></td>
<td width="78%">
<p>Selects binary input. Append <b>s</b> for single
precision [Default is <b>d</b> (double)]. Uppercase <b>S</b>
or <b>D</b> will force byte-swapping. Optionally, append
<i>ncol</i>, the number of columns in your binary input file
if it exceeds the columns needed by the program. Or append
<b>c</b> if the input file is netCDF. Optionally, append
<i>var1</i><b>/</b><i>var2</i><b>/</b><i>...</i> to specify
the variables to be read. [Default is 4 input columns unless
<b>−A</b> is used].</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p><b>−bo</b></p></td>
<td width="7%"></td>
<td width="78%">
<p>Selects binary output. Append <b>s</b> for single
precision [Default is <b>d</b> (double)]. Uppercase <b>S</b>
or <b>D</b> will force byte-swapping. Optionally, append
<i>ncol</i>, the number of desired columns in your binary
output file. [Default is reflected by <b>−F</b>].</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p><b>−m</b></p></td>
<td width="7%"></td>
<td width="78%">
<p>Multiple segment file(s). Segments are separated by a
special record. For ASCII files the first character must be
<i>flag</i> [Default is ’>’]. For binary
files all fields must be NaN and <b>−b</b> must set
the number of output columns explicitly. By default the
<b>−m</b> setting applies to both input and output.
Use <b>−mi</b> and <b>−mo</b> to give separate
settings to input and output.</p></td></tr>
</table>
<h2>TIME SETTINGS
<a name="TIME SETTINGS"></a>
</h2>
<p style="margin-left:11%; margin-top: 1em">If binary input
files are used then absolute time are stored as time
relative to the selected epoch. However, since the epoch
used is not stored in the data files there can be problems
decoding the correct time. The mgd77 supplement uses the
Unix time system as its default; thus you should make sure
that binary data files with time uses the same system (see
the GMT default TIME_SYSTEM).</p>
<h2>EXAMPLES
<a name="EXAMPLES"></a>
</h2>
<p style="margin-left:11%; margin-top: 1em">To get the CM4
Total field, Declination and Inclination due to all but
lithospheric and toroidal field at a one point location and
decimal time 2000.0, try</p>
<p style="margin-left:11%; margin-top: 1em">echo -28 38 0
2000.0 | <b>mgd77magref −A</b>+y <b>−F</b>
tdi/13456</p>
<p style="margin-left:11%; margin-top: 1em">To do the same
as above but at noon (Universal Time) of first May 2001,
try</p>
<p style="margin-left:11%; margin-top: 1em">echo -28 38 0
2001-05-01T12:00:00 | <b>mgd77magref −F</b>
tdi/13456</p>
<h2>SEE ALSO
<a name="SEE ALSO"></a>
</h2>
<p style="margin-left:11%; margin-top: 1em"><i><A HREF="GMT.html">GMT</A></i>(1)
<i><A HREF="mgd77info.html">mgd77info</A></i>(1) <i><A HREF="mgd77list.html">mgd77list</A></i>(1)
<i><A HREF="mgd77manage.html">mgd77manage</A></i>(1) <i><A HREF="mgd77track.html">mgd77track</A></i>(1)</p>
<h2>REFERENCES
<a name="REFERENCES"></a>
</h2>
<p style="margin-left:11%; margin-top: 1em">Wessel, P., and
W. H. F. Smith, 2014, The Generic Mapping Tools (GMT)
version 4.5.12 Technical Reference & Cookbook,
SOEST/NOAA. <br>
Wessel, P., and W. H. F. Smith, 1998, New, Improved Version
of Generic Mapping Tools Released, EOS Trans., AGU, 79 (47),
p. 579. <br>
Wessel, P., and W. H. F. Smith, 1995, New Version of the
Generic Mapping Tools Released, EOS Trans., AGU, 76 (33), p.
329. <br>
Wessel, P., and W. H. F. Smith, 1995, New Version of the
Generic Mapping Tools Released,
http://www.agu.org/eos_elec/95154e.html, Copyright 1995 by
the American Geophysical Union. <br>
Wessel, P., and W. H. F. Smith, 1991, Free Software Helps
Map and Display Data, EOS Trans., AGU, 72 (41), p. 441. <br>
"Comprehensive Modeling of the Geomagnetic Field",
see <i>http://denali.gsfc.nasa.gov/cm/</i>. <br>
"The International Geomagnetic Reference Field
(IGRF)", see
<i>http://www.iugg.org/IAGA/iaga_pages/pubs_prods/igrf.htm</i>.</p>
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