4 files changed, 54 insertions, 1 deletions
diff --git a/src/Makefile.am b/src/Makefile.am
index eaf6bd38..359f2f28 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -53,7 +53,7 @@ libproj_la_SOURCES = \
 	PJ_cass.c PJ_cc.c PJ_cea.c PJ_eqc.c PJ_gall.c PJ_geoc.c \
 	PJ_labrd.c PJ_lsat.c PJ_misrsom.c PJ_merc.c \
 	PJ_mill.c PJ_ocea.c PJ_omerc.c PJ_somerc.c \
-	PJ_tcc.c PJ_tcea.c PJ_times.c PJ_tmerc.c \
+	PJ_tcc.c PJ_tcea.c PJ_times.c PJ_tmerc.c PJ_tobmerc.c \
 	PJ_airy.c PJ_aitoff.c PJ_august.c PJ_bacon.c \
 	PJ_bertin1953.c PJ_chamb.c PJ_hammer.c PJ_lagrng.c PJ_larr.c \
 	PJ_lask.c PJ_latlong.c PJ_nocol.c PJ_ob_tran.c PJ_oea.c \
diff --git a/src/PJ_tobmerc.c b/src/PJ_tobmerc.c
new file mode 100644
index 00000000..9c939f0b
--- /dev/null
+++ b/src/PJ_tobmerc.c
@@ -0,0 +1,51 @@
+#define PJ_LIB__
+
+#include <float.h>
+#include <math.h>
+
+#include "proj_internal.h"
+#include "proj.h"
+#include "proj_math.h"
+#include "projects.h"
+
+PROJ_HEAD(tobmerc, "Tobler-Mercator") "\n\tCyl, Sph";
+
+#define EPS10 1.e-10
+static double logtanpfpim1(double x) {       /* log(tan(x/2 + M_FORTPI)) */
+    if (fabs(x) <= DBL_EPSILON) {
+        /* tan(M_FORTPI + .5 * x) can be approximated by  1.0 + x */
+        return log1p(x);
+    }
+    return log(tan(M_FORTPI + .5 * x));
+}
+
+static XY s_forward (LP lp, PJ *P) {           /* Spheroidal, forward */
+    XY xy = {0.0, 0.0};
+    double cosphi;
+
+    if (fabs(fabs(lp.phi) - M_HALFPI) <= EPS10) {
+        proj_errno_set(P, PJD_ERR_TOLERANCE_CONDITION);
+        return xy;
+    }
+
+    cosphi = cos(lp.phi);
+    xy.x = P->k0 * lp.lam * cosphi * cosphi;
+    xy.y = P->k0 * logtanpfpim1(lp.phi);
+    return xy;
+}
+
+static LP s_inverse (XY xy, PJ *P) {           /* Spheroidal, inverse */
+    LP lp = {0.0, 0.0};
+    double cosphi;
+
+    lp.phi = atan(sinh(xy.y / P->k0));
+    cosphi = cos(lp.phi);
+    lp.lam = xy.x / P->k0 / (cosphi * cosphi);
+    return lp;
+}
+
+PJ *PROJECTION(tobmerc) {
+    P->inv = s_inverse;
+    P->fwd = s_forward;
+    return P;
+}
diff --git a/src/lib_proj.cmake b/src/lib_proj.cmake
index 3e1a17ad..6a287a43 100644
--- a/src/lib_proj.cmake
+++ b/src/lib_proj.cmake
@@ -141,6 +141,7 @@ SET(SRC_LIBPROJ_PJ
         PJ_tcea.c
         PJ_times.c
         PJ_tmerc.c
+        PJ_tobmerc.c
         PJ_tpeqd.c
         PJ_unitconvert.c
         PJ_urm5.c
diff --git a/src/pj_list.h b/src/pj_list.h
index cd19d300..8c72dd1f 100644
--- a/src/pj_list.h
+++ b/src/pj_list.h
@@ -140,6 +140,7 @@ PROJ_HEAD(tcea, "Transverse Cylindrical Equal Area")
 PROJ_HEAD(times, "Times Projection")
 PROJ_HEAD(tissot, "Tissot Conic")
 PROJ_HEAD(tmerc, "Transverse Mercator")
+PROJ_HEAD(tobmerc, "Tobler-Mercator")
 PROJ_HEAD(tpeqd, "Two Point Equidistant")
 PROJ_HEAD(tpers, "Tilted perspective")
 PROJ_HEAD(unitconvert, "Unit conversion")