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geomag70_linux/README.txt

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