Link to USGS home page.
Scientific Investigations Report 2005–5045: Equation 6

The regression finds the coefficients by fitting the dot product to 1 (minimizing the angle between unit vectors), mathematically collineating the two coordinate systems, according to this equation:

 

( H1n ⁄ H1n ) · ( Bkn ⁄ Bkn) = 1

USA.gov logo