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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>
<a name="NAME"></a>
<h2>NAME</h2>
<p style="margin-left:11%; margin-top: 1em">mgd77magref
− Evaluate the IGRF or CM4 magnetic field models</p>
<a name="SYNOPSIS"></a>
<h2>SYNOPSIS</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>
<a name="DESCRIPTION"></a>
<h2>DESCRIPTION</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>
<a name="OPTIONS"></a>
<h2>OPTIONS</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 style="margin-top: 1em" valign="top"><b>−A</b></p> </td>
<td width="8%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">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 valign="top" align="left">
<td width="11%"></td>
<td width="3%">
<p style="margin-top: 1em" valign="top"><b>−C</b></p> </td>
<td width="8%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">Specify an
alternate CM4 coefficient file [umdl.CM4].</p></td>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="3%">
<p style="margin-top: 1em" valign="top"><b>−D</b></p> </td>
<td width="8%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">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 valign="top" align="left">
<td width="11%"></td>
<td width="3%">
<p style="margin-top: 1em" valign="top"><b>−E</b></p> </td>
<td width="8%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">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 valign="top" align="left">
<td width="11%"></td>
<td width="3%">
<p style="margin-top: 1em" valign="top"><b>−F</b></p> </td>
<td width="8%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">Selects output
items; <i>flags</i> is a string made up of one or more of
these characters:</p></td>
</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" valign="top"><b>−G</b></p> </td>
<td width="8%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">Specifies that
coordinates are geocentric [geodetic].</p></td>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="3%">
<p style="margin-top: 1em" valign="top"><b>−H</b></p> </td>
<td width="8%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">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 valign="top" align="left">
<td width="11%"></td>
<td width="3%">
<p style="margin-top: 1em" valign="top"><b>−L</b></p> </td>
<td width="8%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">Computes J field
vectors from certain external sources.</p></td>
</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" valign="top"><b>−Sc</b></p> </td>
<td width="7%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">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 valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p style="margin-top: 1em" valign="top"><b>−Sl</b></p> </td>
<td width="7%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">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 valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p style="margin-top: 1em" valign="top"><b>−V</b></p> </td>
<td width="7%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">Selects verbose
mode, which will send progress reports to stderr [Default
runs "silently"].</p></td>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p style="margin-top: 1em" valign="top"><b>−:</b></p> </td>
<td width="7%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">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 valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p style="margin-top: 1em" valign="top"><b>−bi</b></p> </td>
<td width="7%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">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 valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p style="margin-top: 1em" valign="top"><b>−bo</b></p> </td>
<td width="7%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">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 valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p style="margin-top: 1em" valign="top"><b>−m</b></p> </td>
<td width="7%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">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>
</table>
<a name="TIME SETTINGS"></a>
<h2>TIME SETTINGS</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>
<a name="EXAMPLES"></a>
<h2>EXAMPLES</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>
<a name="SEE ALSO"></a>
<h2>SEE ALSO</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>
<a name="REFERENCES"></a>
<h2>REFERENCES</h2>
<p style="margin-left:11%; margin-top: 1em">Wessel, P., and
W. H. F. Smith, 2013, The Generic Mapping Tools (GMT)
version 4.5.11 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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