1 files changed, 44 insertions, 0 deletions
diff --git a/src/PJ_glabsgm.c b/src/PJ_glabsgm.c
new file mode 100644
index 00000000..d094239c
--- /dev/null
+++ b/src/PJ_glabsgm.c
@@ -0,0 +1,44 @@
+#ifndef lint
+static const char SCCSID[]="@(#)PJ_glabsgm.c	4.5	07/09/24	???	???";
+#endif
+#define PROJ_PARMS__ \
+	double lamc;\
+	double phic;\
+	double c;\
+	double n1;\
+	double n2;
+
+#define PJ_LIB__
+# include	<projects.h>
+PROJ_HEAD(glabsgm, "Gauss Laborde (Sphere Geometric Mean)")
+	"\n\tCyl, Sph&Ell\n\tlat_0= lon_0= k_0=";
+FORWARD(s_forward); /* spheroid */
+	double L, Ls, sinLs1, Ls1;
+	L= P->n1*lp.lam;
+        Ls= P->c+P->n1*log(pj_tsfn(-1.0*lp.phi,-1.0*sin(lp.phi),P->e));
+        sinLs1= sin(L)/cosh(Ls);
+        Ls1= log(pj_tsfn(-1.0*asin(sinLs1),0.0,0.0));
+        xy.x= P->n2*P->ra*Ls1;
+        xy.y= P->n2*P->ra*atan(sinh(Ls)/cos(L));
+	return (xy);
+}
+INVERSE(s_inverse); /* spheroid */
+	double L, LC, sinC;
+	L= atan(sinh(xy.x*P->a/P->n2)/cos(xy.y*P->a/P->n2));
+        sinC= sin(xy.y*P->a/P->n2)/cosh(xy.x*P->a/P->n2);
+        LC= log(pj_tsfn(-1.0*asin(sinC),0.0,0.0));
+        lp.lam= L/P->n1;
+        lp.phi= -1.0*pj_phi2(exp((LC-P->c)/P->n1),P->e);
+	return (lp);
+}
+FREEUP; if (P) pj_dalloc(P); }
+ENTRY0(glabsgm)
+        P->n1= sqrt(1.0+P->es*pow(cos(P->phi0),4.0)/(1.0-P->es));
+        P->phic= asin(sin(P->phi0)/P->n1);
+        P->c=       log(pj_tsfn(-1.0*P->phic,0.0,0.0))
+             -P->n1*log(pj_tsfn(-1.0*P->phi0,-1.0*sin(P->phi0),P->e));
+        P->n2= P->k0*P->a*sqrt(1.0-P->es)/(1.0-P->es*sin(P->phi0)*sin(P->phi0));
+        P->y0-= P->n2*P->phic;
+	P->inv= s_inverse;
+	P->fwd= s_forward;
+ENDENTRY(P)