Editing CHAMP dewarp equations

CHAMP Dewarp Equations 
John Monnier
written up 2010May26

based on idea that the fringe frequency is known and the opd steps in the ABCD are known but not equally spaced.

So assume we have a fringe of spatial frequency <math>k_0 = \frac{2 \pi}{\lambda_0}<\math> and true phase <math>\phi_0<\math>.  Then the true fringe intensity:

<math> 
I_i = A_0 sin (2 \pi k_0 x_i - \phi_0 ) + I_0
<\math>

The true quadrature terms X,Y are then:
<math> X_0 = -A_0 sin(\phi_0) 
Y_0 = A_0 cos(\phi_0)
<\math>