pe_delta_center

Adjusts (l - l0) to within ±p of the center longitude

double pe_delta_center (double lam, double center_lam);

lam	Longitude of the current point
center_lam	Longitude to center around

Ensures that the difference between the longitude of the current point and central longitude (l - l0) remains within ±p during calculations.

Returns a value between ±p of the center_lam value