Add webmerc projection

OSGeo · Apr 7, 2018 · 51df307 · 51df307
1 parent 3355c67
commit 51df307
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Showing 5 changed files with 38 additions and 1 deletion.
diff --git a/docs/source/operations/projections/index.rst b/docs/source/operations/projections/index.rst
@@ -141,6 +141,7 @@ Projections map the spherical 3D space to a flat 2D space.
    wag5
    wag6
    wag7
+   webmerc
    weren
    wink1
    wink2

diff --git a/docs/source/operations/projections/merc.rst b/docs/source/operations/projections/merc.rst
@@ -29,9 +29,11 @@ The projection is conformal which makes it suitable for navigational purposes.
 |                     | datum is ellipsoidal.                                    |
 |                     |                                                          |
 |                     | * aux_sphere_type=0 will use the semi-major radius.      |
-|                     |   This is the value to use for Google Web Mercator::     |
+|                     |   This is the value to use for Web Mercator::            |
 |                     |                                                          |
 |                     |     proj=merc +datum=WGS84 +aux_sphere_type=0            |
+|                     |                                                          |
+|                     |   You can also use the :ref:`webmerc` projection.        |
 |                     | * aux_sphere_type=1 will use the semi-minor radius.      |
 |                     | * aux_sphere_type=2 will calculate the authalic radius   |
 |                     |   and use it.                                            |

diff --git a/src/PJ_merc.c b/src/PJ_merc.c
@@ -4,6 +4,7 @@
 #include "projects.h"
 
 PROJ_HEAD(merc, "Mercator") "\n\tCyl, Sph&Ell\n\tlat_ts= aux_sphere_type=";
+PROJ_HEAD(webmerc, "Web Mercator / Pseudo Mercator") "\n\tCyl, Sph\n\t";
 
 #define EPS10 1.e-10
 
@@ -118,3 +119,22 @@ PJ *PROJECTION(merc) {
     return P;
 }
 
+PJ *PROJECTION(webmerc) {
+
+    if( pj_param(P->ctx, P->params, "tk_0").i ) {
+        return pj_default_destructor(P, PJD_ERR_INVALID_ARG);
+    }
+
+    if( pj_param(P->ctx, P->params, "tlat_s").i ) {
+        return pj_default_destructor(P, PJD_ERR_INVALID_ARG);
+    }
+
+    if( pj_param(P->ctx, P->params, "tlat_0").i ) {
+        return pj_default_destructor(P, PJD_ERR_INVALID_ARG);
+    }
+
+    pj_calc_ellipsoid_params (P, P->a, 0);
+    P->inv = s_inverse;
+    P->fwd = s_forward;
+    return P;
+}
diff --git a/src/pj_list.h b/src/pj_list.h
@@ -156,6 +156,7 @@ PROJ_HEAD(wag4, "Wagner IV")
 PROJ_HEAD(wag5, "Wagner V")
 PROJ_HEAD(wag6, "Wagner VI")
 PROJ_HEAD(wag7, "Wagner VII")
+PROJ_HEAD(webmerc, "Web Mercator / Pseudo Mercator")
 PROJ_HEAD(weren, "Werenskiold I")
 PROJ_HEAD(wink1, "Winkel I")
 PROJ_HEAD(wink2, "Winkel II")

diff --git a/test/gie/4D-API_cs2cs-style.gie b/test/gie/4D-API_cs2cs-style.gie
@@ -228,6 +228,19 @@ accept      487147.594520173    4934316.46263998    0
 expect      -10370728.80        5552839.74          0
 -------------------------------------------------------------------------------
 
+-------------------------------------------------------------------------------
+Test that Google's Web Mercator with +proj=webmerc
+-------------------------------------------------------------------------------
+operation   proj=pipeline step init=epsg:26915 inv step proj=webmerc datum=WGS84
+-------------------------------------------------------------------------------
+tolerance   20 cm
+accept      487147.594520173    4934316.46263998
+expect      -10370728.80        5552839.74
+
+accept      487147.594520173    4934316.46263998    0
+expect      -10370728.80        5552839.74          0
+-------------------------------------------------------------------------------
+
 -------------------------------------------------------------------------------
 Test that +datum parameters are handled correctly in pipelines.
 See #872 for details.