1 files changed, 22 insertions, 11 deletions
diff --git a/src/iso19111/c_api.cpp b/src/iso19111/c_api.cpp
index 4fedbe05..f5f7ba55 100644
--- a/src/iso19111/c_api.cpp
+++ b/src/iso19111/c_api.cpp
@@ -1810,7 +1810,8 @@ PJ *proj_crs_create_bound_crs_to_WGS84(PJ_CONTEXT *ctx, const PJ *crs,
 
 // ---------------------------------------------------------------------------
 
-/** \brief Returns a BoundCRS, with a transformation to EPSG:4979 using a grid.
+/** \brief Returns a BoundCRS, with a transformation to a hub geographic 3D crs
+ * (use EPSG:4979 for WGS84 for example), using a grid.
  *
  * The returned object must be unreferenced with proj_destroy() after
  * use.
@@ -1818,33 +1819,43 @@ PJ *proj_crs_create_bound_crs_to_WGS84(PJ_CONTEXT *ctx, const PJ *crs,
  *
  * @param ctx PROJ context, or NULL for default context
  * @param vert_crs Object of type VerticalCRS (must not be NULL)
+ * @param hub_geographic_3D_crs Object of type Geographic 3D CRS (must not be
+ * NULL)
  * @param grid_name Grid name (typically a .gtx file)
  * @return Object that must be unreferenced with proj_destroy(), or NULL
  * in case of error.
  * @since 7.0
  */
-PJ *proj_crs_create_bound_vertical_crs_to_WGS84(PJ_CONTEXT *ctx,
-                                                const PJ *vert_crs,
-                                                const char *grid_name) {
+PJ *proj_crs_create_bound_vertical_crs(PJ_CONTEXT *ctx, const PJ *vert_crs,
+                                       const PJ *hub_geographic_3D_crs,
+                                       const char *grid_name) {
     SANITIZE_CTX(ctx);
     assert(vert_crs);
+    assert(hub_geographic_3D_crs);
     assert(grid_name);
     auto l_crs = std::dynamic_pointer_cast<VerticalCRS>(vert_crs->iso_obj);
     if (!l_crs) {
-        proj_log_error(ctx, __FUNCTION__, "Object is not a VerticalCRS");
+        proj_log_error(ctx, __FUNCTION__, "vert_crs is not a VerticalCRS");
+        return nullptr;
+    }
+    auto hub_crs =
+        std::dynamic_pointer_cast<CRS>(hub_geographic_3D_crs->iso_obj);
+    if (!hub_crs) {
+        proj_log_error(ctx, __FUNCTION__, "hub_geographic_3D_crs is not a CRS");
         return nullptr;
     }
     try {
         auto nnCRS = NN_NO_CHECK(l_crs);
+        auto nnHubCRS = NN_NO_CHECK(hub_crs);
         auto transformation =
             Transformation::createGravityRelatedHeightToGeographic3D(
                 PropertyMap().set(IdentifiedObject::NAME_KEY,
-                                  "unknown to WGS84 ellipsoidal height"),
-                nnCRS, GeographicCRS::EPSG_4979, nullptr,
-                std::string(grid_name), std::vector<PositionalAccuracyNNPtr>());
-        return pj_obj_create(
-            ctx,
-            BoundCRS::create(nnCRS, GeographicCRS::EPSG_4979, transformation));
+                                  "unknown to " + hub_crs->nameStr() +
+                                      " ellipsoidal height"),
+                nnCRS, nnHubCRS, nullptr, std::string(grid_name),
+                std::vector<PositionalAccuracyNNPtr>());
+        return pj_obj_create(ctx,
+                             BoundCRS::create(nnCRS, nnHubCRS, transformation));
     } catch (const std::exception &e) {
         proj_log_error(ctx, __FUNCTION__, e.what());
         if (ctx->cpp_context) {