Coordinate transformation: improve transformations from/to WGS84 (Gxxxx)

Currently very few transformations from/to WGS84 (Gxxxx) are registered
in the EPSG database, and there isn't even transformations between WGS84 EPSG:4326
and those ones. Consequently transformations to those realizations often
ended up as no-operation, whereas going through WGS84 EPSG:4326 will bring
more meaningful results. So register those EPSG:4326<-->WGS 84 (Gxxx)
null transformations, and when having WGS 84 (Gxxx) as source/target,
consider EPSG:4326 as an intermediate.
This change has no effect on the existing direct transformations
from/to WGS 84 (Gxxx).

1 files changed, 23 insertions, 0 deletions

diff --git a/src/iso19111/factory.cpp b/src/iso19111/factory.cpp
index 1f40f1f0..4bf5427d 100644
--- a/src/iso19111/factory.cpp
+++ b/src/iso19111/factory.cpp
@@ -4982,6 +4982,29 @@ AuthorityFactory::createCompoundCRSFromExisting(
 // ---------------------------------------------------------------------------
 
 //! @cond Doxygen_Suppress
+std::list<datum::GeodeticReferenceFrameNNPtr>
+AuthorityFactory::getPreferredHubGeodeticReferenceFrames(
+    const std::string &geodeticReferenceFrameCode) const {
+    std::list<datum::GeodeticReferenceFrameNNPtr> res;
+
+    const std::string sql("SELECT hub_auth_name, hub_code FROM "
+                          "geodetic_datum_preferred_hub WHERE "
+                          "src_auth_name = ? AND src_code = ?");
+    auto sqlRes = d->run(sql, {d->authority(), geodeticReferenceFrameCode});
+    for (const auto &row : sqlRes) {
+        const auto &auth_name = row[0];
+        const auto &code = row[1];
+        res.emplace_back(
+            d->createFactory(auth_name)->createGeodeticDatum(code));
+    }
+
+    return res;
+}
+//! @endcond
+
+// ---------------------------------------------------------------------------
+
+//! @cond Doxygen_Suppress
 FactoryException::FactoryException(const char *message) : Exception(message) {}
 
 // ---------------------------------------------------------------------------