96 lines
3.7 KiB
Plaintext
96 lines
3.7 KiB
Plaintext
This zip file contains the C source code for the NGDC software "Geomag"
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version 7.0 that computes the estimated main magnetic field values for
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given locations and dates (or ranges of dates). Geomag requires a
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magnetic field model file for input. One model is included in this
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zip: IGRF13.COF. Note that the text file formats differ
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slightly in format between Unix and Windows platforms. Two different
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archives are therefore provided for Unix and Windows. The zip and tar
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files also include compiled versions (executables) of Geomag for
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Windows and Linux. This readme file contains instructions for both
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the Windows and Linux versions.
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Important notice on change of file format
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-----------------------------------------
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The file format of IGRF11.COF and forward had to be changed from the previous
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versions (IGRF10.cof and IGRF10.unx) because the previous format did not
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allow for the new 0.01 nT precision of the DGRF2005 coefficients. In this
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file format revision, we also swapped the previously confusing m,n ordering
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to the standard n,m where n is the degree and m is the order. The format
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was further adjusted to have blanks between all fields, so that values no
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longer run into each other. This makes the files easier to read using
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unformatted read statments.
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Background
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----------
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IGRF13 is the thirteenth generation standard main field model adopted
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by the International Association of Geomagnetism and Aeronomy (IAGA).
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This is a degree and order 10 model from 1900 to 1995 and a degree and
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order 13 model from 2000 to 2025, providing estimates of the main field
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for dates between January 1, 1900 and January 1, 2025. For more information
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on the IGRF and IAGA, visit the IAGA Working Group V-MOD Web site at:
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http://www.ngdc.noaa.gov/IAGA/vmod/
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The computed magnetic elements are:
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-----------------------------------
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D: Declination
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I: Inclination
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H: Horizontal field strength
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X: North component
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Y: East component
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Z: Down component
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F: Total field strength
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dD,dI,dH,dX,dY,dZ,dF: Change per year of the above quantities.
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To compile this code:
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------------------------------------
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Gnu C compiler on Unix:
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gcc geomag70.c -o geomag70.exe
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Intel C on Unix:
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icc geomag70.c -o geomag70.exe
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The Windows .exe file was generated using
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Code Gear C++ 2009 Builder
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Command line option:
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--------------------
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Note that the geomag program can receive parameters on
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the command line. For example:
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geomag70.exe IGRF13.COF 2010.32 D M133.4 10.5 10.5
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The command line syntax is listed by providing the h option as
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geomag70.exe h
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Spread-sheet option:
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--------------------
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Revision 6.1 introduced the option to read a file of
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dates and locations and create a new file with a set of extra
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columns giving the magnetic components. These can then be
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read as columns into a spread sheet program. The dates and
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coordinates have to be given in the same format as for the
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command line option. See also the sample files discussed below.
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For example:
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geomag70.exe IGRF13.COF f in-coords.txt output.txt
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will append the magnetic components and their secular
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variation to the dates and locations given in 'in-coords.txt'
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and write the result to a file 'output.txt'.
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This distribution contains example files which were produced
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on a Linux system using the commands:
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geomag70.exe IGRF13.COF f sample_coords.txt sample_out_IGRF13.txt
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To run the program with command line arguments under Windows:
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-------------------------------------------------------------
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1) Click on <Start> <Programs> <Accessories> <Command Prompt>
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2) Change directory ('cd') to the folder containg geomag70.exe
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3) Run the program, e.g. 'geomag70.exe IGRF13.COF f in.txt out.txt'
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Contact:
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--------
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For further infos, or bug reports, please contact:
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geomag.models@noaa.gov
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