CGM

Corrected Geomagnetic - A coordinate systemfrom a spatial point with GEO radial distance and geomagnetic latitude andlongitude, follow the epoch-appropriate IGRF/DGRF model field vector throughto the point where the field line crosses the geomagnetic dipole equatorialplane. Then trace the dipole magnetic field vector Earthward from that pointon the equatorial plane, in the same hemisphere as the original point, untilthe initial radial distance is reached. Designate the dipole latitude andlongitude at that point as the CGM latitude and longitude of the originalpoint. See http://nssdc.gsfc.nasa.gov/space/cgm/cgmm_des.html