This zip file contains the C source code for the NGDC software "Geomag" 
version 6.0 (October 2005).  Geomag computes the estimated magnetic field 
values due to the main (internal) field for a given location and data 
(or range of dates).  Geomag requires a magnetic field model file for input.  
Two models are included in this zip: 
       IGRF10 and WMM2005.  

The zip file also includes the compiled version of Geomag, which should 
run on DOS and Linux machines.  

The IGRF10 is the tenth generation standard main field model adopted 
by the International Association of Geomagnetism and Aeronomy (IAGA).  
This is a degree and order 13 model for 2005-2010 with models for 1900 
forward enabling estimation of the main field for dates between 
January 1, 1900 and January 1, 2010. 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 WMM is the standard model for the U.S. and U.K. Departments of Defense  
and for NATO.  This is a degree and order 12 main field model for 2005.0 
and degree and order 12 (computed to 8) secular variation model for 2005 - 
2010. For more information on the WMM or to download the Technical Report, 
visit the WMM Web site at:
        http://www.ngdc.noaa.gov/seg/WMM/

     

Note that the geomag program can receive parameters on 
the command line. For example:

geomag60 igrf10.cof 2005.5 D K1.6 40.0 -105.0
would use the igrf10 model to compute the magnetic field for 2005.5 at 1.6km 
geodetic altitude for 40 degrees north and 105 degrees west.  The command line
format is:
program model_file coordinate_system altitudeunit_value lat_decdeg lon_decdeg
  where D = geodetic C = geocentric and 
    K(kilometers) M(meters) F(feet) followed by altitude with no space

