createOperations(): follow-up of previous commit for +datum=NAD83 case

2 files changed, 60 insertions, 7 deletions

diff --git a/src/iso19111/crs.cpp b/src/iso19111/crs.cpp
index ad4acaff..60b316f1 100644
--- a/src/iso19111/crs.cpp
+++ b/src/iso19111/crs.cpp
@@ -1323,7 +1323,12 @@ void GeodeticCRS::addDatumInfoToPROJString(
                        datum::GeodeticReferenceFrame::EPSG_6269.get(),
                        util::IComparable::Criterion::EQUIVALENT)) {
             datumWritten = true;
-            formatter->addParam("datum", "NAD83");
+            if (formatter->getLegacyCRSToCRSContext()) {
+                // We do not want datum=NAD83 to cause a useless towgs84=0,0,0
+                formatter->addParam("ellps", "GRS80");
+            } else {
+                formatter->addParam("datum", "NAD83");
+            }
         }
     }
     if (!datumWritten) {
@@ -2084,28 +2089,28 @@ void GeographicCRS::_exportToPROJString(
         !formatter->getTOWGS84Parameters().empty() ||
         !formatter->getHDatumExtension().empty()) {
 
+        formatter->addStep("longlat");
         bool done = false;
         if (formatter->getLegacyCRSToCRSContext() &&
             formatter->getHDatumExtension().empty() &&
             formatter->getTOWGS84Parameters().empty()) {
-            done = true;
             const auto &l_datum = datum();
             if (l_datum &&
                 l_datum->_isEquivalentTo(
                     datum::GeodeticReferenceFrame::EPSG_6326.get(),
                     util::IComparable::Criterion::EQUIVALENT)) {
-                formatter->addStep("longlat");
+                done = true;
                 formatter->addParam("ellps", "WGS84");
             } else if (l_datum &&
                        l_datum->_isEquivalentTo(
-                           datum::GeodeticReferenceFrame::EPSG_6267.get(),
+                           datum::GeodeticReferenceFrame::EPSG_6269.get(),
                            util::IComparable::Criterion::EQUIVALENT)) {
-                formatter->addStep("longlat");
-                formatter->addParam("datum", "NAD27");
+                done = true;
+                // We do not want datum=NAD83 to cause a useless towgs84=0,0,0
+                formatter->addParam("ellps", "GRS80");
             }
         }
         if (!done) {
-            formatter->addStep("longlat");
             addDatumInfoToPROJString(formatter);
         }
     }
diff --git a/test/unit/test_operation.cpp b/test/unit/test_operation.cpp
index f95f94bd..89edfca4 100644
--- a/test/unit/test_operation.cpp
+++ b/test/unit/test_operation.cpp
@@ -7090,6 +7090,54 @@ TEST(
 
 // ---------------------------------------------------------------------------
 
+TEST(operation,
+     createOperation_fallback_to_proj4_strings_proj_NAD83_to_projliteral) {
+    auto objSrc = PROJStringParser().createFromPROJString(
+        "+proj=utm +zone=11 +datum=NAD83 +type=crs");
+    auto src = nn_dynamic_pointer_cast<CRS>(objSrc);
+    ASSERT_TRUE(src != nullptr);
+
+    auto objDst = PROJStringParser().createFromPROJString(
+        "+proj=longlat +datum=WGS84 +over +type=crs");
+    auto dst = nn_dynamic_pointer_cast<CRS>(objDst);
+    ASSERT_TRUE(dst != nullptr);
+
+    auto op = CoordinateOperationFactory::create()->createOperation(
+        NN_CHECK_ASSERT(src), NN_CHECK_ASSERT(dst));
+    ASSERT_TRUE(op != nullptr);
+    EXPECT_EQ(op->exportToPROJString(PROJStringFormatter::create().get()),
+              "+proj=pipeline "
+              "+step +inv +proj=utm +zone=11 +ellps=GRS80 "
+              "+step +proj=longlat +datum=WGS84 +over "
+              "+step +proj=unitconvert +xy_in=rad +xy_out=deg");
+}
+
+// ---------------------------------------------------------------------------
+
+TEST(operation,
+     createOperation_fallback_to_proj4_strings_geog_NAD83_to_projliteral) {
+    auto objSrc = PROJStringParser().createFromPROJString(
+        "+proj=longlat +datum=NAD83 +type=crs");
+    auto src = nn_dynamic_pointer_cast<CRS>(objSrc);
+    ASSERT_TRUE(src != nullptr);
+
+    auto objDst = PROJStringParser().createFromPROJString(
+        "+proj=longlat +datum=WGS84 +over +type=crs");
+    auto dst = nn_dynamic_pointer_cast<CRS>(objDst);
+    ASSERT_TRUE(dst != nullptr);
+
+    auto op = CoordinateOperationFactory::create()->createOperation(
+        NN_CHECK_ASSERT(src), NN_CHECK_ASSERT(dst));
+    ASSERT_TRUE(op != nullptr);
+    EXPECT_EQ(op->exportToPROJString(PROJStringFormatter::create().get()),
+              "+proj=pipeline "
+              "+step +proj=unitconvert +xy_in=deg +xy_out=rad "
+              "+step +proj=longlat +datum=WGS84 +over "
+              "+step +proj=unitconvert +xy_in=rad +xy_out=deg");
+}
+
+// ---------------------------------------------------------------------------
+
 TEST(
     operation,
     createOperation_fallback_to_proj4_strings_regular_with_nadgrids_to_projliteral) {