2 files changed, 77 insertions, 1 deletions
diff --git a/src/projections/col_urban.cpp b/src/projections/col_urban.cpp
new file mode 100644
index 00000000..5bc8407f
--- /dev/null
+++ b/src/projections/col_urban.cpp
@@ -0,0 +1,76 @@
+#define PJ_LIB__
+
+#include <errno.h>
+#include <math.h>
+
+#include "proj.h"
+#include "proj_internal.h"
+
+PROJ_HEAD(col_urban, "Colombia Urban")
+    "\n\tMisc\n\th_0=";
+
+// Notations and formulas taken from IOGP Publication 373-7-2 -
+// Geomatics Guidance Note number 7, part 2 - March 2020
+
+namespace { // anonymous namespace
+
+struct pj_opaque {
+    double h0; // height of projection origin, divided by semi-major axis (a)
+    double rho0; // adimensional value, contrary to Guidance note 7.2
+    double A;
+    double B; // adimensional value, contrary to Guidance note 7.2
+    double C;
+    double D; // adimensional value, contrary to Guidance note 7.2
+};
+} // anonymous namespace
+
+static PJ_XY col_urban_forward (PJ_LP lp, PJ *P) {
+    PJ_XY xy;
+    struct pj_opaque *Q = static_cast<struct pj_opaque*>(P->opaque);
+
+    const double cosphi = cos(lp.phi);
+    const double sinphi = sin(lp.phi);
+    const double nu = 1. / sqrt(1 - P->es * sinphi * sinphi);
+    const double lam_nu_cosphi = lp.lam * nu * cosphi;
+    xy.x = Q->A * lam_nu_cosphi;
+    const double sinphi_m = sin(0.5 * (lp.phi + P->phi0));
+    const double rho_m = (1 - P->es) / pow(1 - P->es * sinphi_m * sinphi_m, 1.5);
+    const double G = 1 + Q->h0 / rho_m;
+    xy.y = G * Q->rho0 * ((lp.phi - P->phi0) + Q->B * lam_nu_cosphi * lam_nu_cosphi);
+
+    return xy;
+}
+
+static PJ_LP col_urban_inverse (PJ_XY xy, PJ *P) {
+    PJ_LP lp;
+    struct pj_opaque *Q = static_cast<struct pj_opaque*>(P->opaque);
+
+    lp.phi = P->phi0 + xy.y / Q->D - Q->B * (xy.x / Q->C) * (xy.x / Q->C);
+    const double sinphi = sin(lp.phi);
+    const double nu = 1. / sqrt(1 - P->es * sinphi * sinphi);
+    lp.lam = xy.x / (Q->C * nu * cos(lp.phi));
+
+    return lp;
+}
+
+PJ *PROJECTION(col_urban) {
+    struct pj_opaque *Q = static_cast<struct pj_opaque*>(pj_calloc (1, sizeof (struct pj_opaque)));
+    if (nullptr==Q)
+        return pj_default_destructor (P, ENOMEM);
+    P->opaque = Q;
+
+    const double h0_unscaled = pj_param(P->ctx, P->params, "dh_0").f;
+    Q->h0 = h0_unscaled / P->a;
+    const double sinphi0 = sin(P->phi0);
+    const double nu0 = 1. / sqrt(1 - P->es * sinphi0 * sinphi0);
+    Q->A = 1 + Q->h0 / nu0;
+    Q->rho0 = (1 - P->es) / pow(1 - P->es * sinphi0 * sinphi0, 1.5);
+    Q->B = tan(P->phi0) / (2 * Q->rho0 * nu0);
+    Q->C = 1 + Q->h0;
+    Q->D = Q->rho0 * (1 + Q->h0 / (1 - P->es));
+
+    P->fwd = col_urban_forward;
+    P->inv = col_urban_inverse;
+
+    return P;
+}
diff --git a/src/projections/ortho.cpp b/src/projections/ortho.cpp
index 75b8199d..8dcfb53c 100644
--- a/src/projections/ortho.cpp
+++ b/src/projections/ortho.cpp
@@ -223,7 +223,7 @@ static PJ_LP ortho_e_inverse (PJ_XY xy, PJ *P) {           /* Ellipsoidal, inver
 
     // Using Q->sinph0 * sinphi + Q->cosph0 * cosphi * coslam == 0 (visibity
     // condition of the forward case) in the forward equations, and a lot of
-    // substition games...
+    // substitution games...
     PJ_XY xy_recentered;
     xy_recentered.x = xy.x;
     xy_recentered.y = (xy.y - Q->y_shift) / Q->y_scale;