Use nm units in builtins.gie. Remove backward looking comments in code.

2 files changed, 8 insertions, 5 deletions

diff --git a/src/phi2.cpp b/src/phi2.cpp
index b9b37765..0fdca47c 100644
--- a/src/phi2.cpp
+++ b/src/phi2.cpp
@@ -116,6 +116,7 @@ double pj_phi2(projCtx ctx, const double ts0, const double e) {
    * Determine latitude angle phi-2.
    * Inputs:
    *   ts = exp(-psi) where psi is the isometric latitude (dimensionless)
+   *        this variable is defined in Snyder (1987), Eq. (7-10)
    *   e = eccentricity of the ellipsoid (dimensionless)
    * Output:
    *   phi = geographic latitude (radians)
@@ -123,13 +124,12 @@ double pj_phi2(projCtx ctx, const double ts0, const double e) {
    *   psi = log( tan(pi/4 + phi/2) *
    *              ( (1 - e*sin(phi)) / (1 + e*sin(phi)) )^(e/2) )
    *       = asinh(tan(phi)) - e * atanh(e * sin(phi))
+   *       = asinh(tan(chi))
+   *   chi = conformal latitude
    *
-   * OLD: This routine inverts this relation using the iterative scheme given
-   * by Snyder (1987), Eqs. (7-9) - (7-11).
+   * This routine converts t = exp(-psi) to
    *
-   * NEW: This routine converts t = exp(-psi) to
-   *
-   *   tau' = sinh(psi) = (1/t - t)/2
+   *   tau' = tan(chi) = sinh(psi) = (1/t - t)/2
    *
    * returns atan(sinpsi2tanphi(tau'))
    ***************************************************************************/
diff --git a/src/tsfn.cpp b/src/tsfn.cpp
index a0960a66..8ed258d6 100644
--- a/src/tsfn.cpp
+++ b/src/tsfn.cpp
@@ -11,10 +11,13 @@ double pj_tsfn(double phi, double sinphi, double e) {
    *   e = eccentricity of the ellipsoid (dimensionless)
    * Output:
    *   ts = exp(-psi) where psi is the isometric latitude (dimensionless)
+   *      = 1 / (tan(chi) + sec(chi))
    * Here isometric latitude is defined by
    *   psi = log( tan(pi/4 + phi/2) *
    *              ( (1 - e*sin(phi)) / (1 + e*sin(phi)) )^(e/2) )
    *       = asinh(tan(phi)) - e * atanh(e * sin(phi))
+   *       = asinh(tan(chi))
+   *   chi = conformal latitude
    ***************************************************************************/
 
     double cosphi = cos(phi);