C API: add proj_dynamic_datum_get_frame_reference_epoch()

4 files changed, 42 insertions, 0 deletions

diff --git a/scripts/reference_exported_symbols.txt b/scripts/reference_exported_symbols.txt
index 6cb20c08..8f225b3b 100644
--- a/scripts/reference_exported_symbols.txt
+++ b/scripts/reference_exported_symbols.txt
@@ -989,6 +989,7 @@ proj_degree_output
 proj_destroy
 proj_dmstor
 proj_download_file
+proj_dynamic_datum_get_frame_reference_epoch
 proj_ellipsoid_get_parameters
 proj_errno
 proj_errno_reset
diff --git a/src/iso19111/c_api.cpp b/src/iso19111/c_api.cpp
index c152df88..cad76431 100644
--- a/src/iso19111/c_api.cpp
+++ b/src/iso19111/c_api.cpp
@@ -8163,6 +8163,40 @@ PJ *proj_crs_get_datum_forced(PJ_CONTEXT *ctx, const PJ *crs) {
 
 // ---------------------------------------------------------------------------
 
+/** \brief Returns the frame reference epoch of a dynamic geodetic or vertical
+ * reference frame.
+ *
+ * @param ctx PROJ context, or NULL for default context
+ * @param datum Object of type DynamicGeodeticReferenceFrame or
+ * DynamicVerticalReferenceFrame (must not be NULL)
+ * @return the frame reference epoch as decimal year, or -1 in case of error.
+ *
+ * @since 7.2
+ */
+double proj_dynamic_datum_get_frame_reference_epoch(PJ_CONTEXT *ctx,
+                                                    const PJ *datum) {
+    SANITIZE_CTX(ctx);
+    if (!datum) {
+        proj_log_error(ctx, __FUNCTION__, "missing required input");
+        return -1;
+    }
+    auto dgrf = dynamic_cast<const DynamicGeodeticReferenceFrame *>(
+        datum->iso_obj.get());
+    auto dvrf = dynamic_cast<const DynamicVerticalReferenceFrame *>(
+        datum->iso_obj.get());
+    if (!dgrf && !dvrf) {
+        proj_log_error(ctx, __FUNCTION__, "Object is not a "
+                                          "DynamicGeodeticReferenceFrame or "
+                                          "DynamicVerticalReferenceFrame");
+        return -1;
+    }
+    const auto &frameReferenceEpoch =
+        dgrf ? dgrf->frameReferenceEpoch() : dvrf->frameReferenceEpoch();
+    return frameReferenceEpoch.value();
+}
+
+// ---------------------------------------------------------------------------
+
 /** \brief Returns the coordinate system of a SingleCRS.
  *
  * The returned object must be unreferenced with proj_destroy() after
diff --git a/src/proj.h b/src/proj.h
index 92966526..b758663a 100644
--- a/src/proj.h
+++ b/src/proj.h
@@ -1263,6 +1263,9 @@ PJ PROJ_DLL *proj_datum_ensemble_get_member(PJ_CONTEXT *ctx,
                                             const PJ *datum_ensemble,
                                             int member_index);
 
+double PROJ_DLL proj_dynamic_datum_get_frame_reference_epoch(PJ_CONTEXT *ctx,
+                                                     const PJ *datum);
+
 PJ PROJ_DLL *proj_crs_get_coordinate_system(PJ_CONTEXT *ctx, const PJ *crs);
 
 PJ_COORDINATE_SYSTEM_TYPE PROJ_DLL proj_cs_get_type(PJ_CONTEXT *ctx,
diff --git a/test/unit/test_c_api.cpp b/test/unit/test_c_api.cpp
index c7053291..c0db3880 100644
--- a/test/unit/test_c_api.cpp
+++ b/test/unit/test_c_api.cpp
@@ -852,6 +852,8 @@ TEST_F(CApi, proj_create_from_database) {
         ObjectKeeper keeper(datum);
         EXPECT_EQ(proj_get_type(datum),
                   PJ_TYPE_DYNAMIC_GEODETIC_REFERENCE_FRAME);
+        EXPECT_EQ(proj_dynamic_datum_get_frame_reference_epoch(m_ctxt, datum),
+                  2005.0);
     }
     {
         // Norway Normal Null 2000
@@ -861,6 +863,8 @@ TEST_F(CApi, proj_create_from_database) {
         ObjectKeeper keeper(datum);
         EXPECT_EQ(proj_get_type(datum),
                   PJ_TYPE_DYNAMIC_VERTICAL_REFERENCE_FRAME);
+        EXPECT_EQ(proj_dynamic_datum_get_frame_reference_epoch(m_ctxt, datum),
+                  2000.0);
     }
     {
         auto op = proj_create_from_database(m_ctxt, "EPSG", "16031",