Merge pull request #1369 from rouault/grid_fixes

Grid related fixes

2 files changed, 15 insertions, 3 deletions

diff --git a/src/iso19111/coordinateoperation.cpp b/src/iso19111/coordinateoperation.cpp
index d7f138a4..50a6a003 100644
--- a/src/iso19111/coordinateoperation.cpp
+++ b/src/iso19111/coordinateoperation.cpp
@@ -8778,13 +8778,25 @@ void Transformation::_exportToPROJString(
         if (fileParameter &&
             fileParameter->type() == ParameterValue::Type::FILENAME) {
             auto filename = fileParameter->valueFile();
-            if (isMethodInverseOf) {
+            bool doInversion = isMethodInverseOf;
+            if (!identifiers().empty() &&
+                *identifiers().front()->codeSpace() ==
+                    metadata::Identifier::EPSG &&
+                method()->nameStr() ==
+                    "Geographic3D to GravityRelatedHeight (US .gtx)" &&
+                ends_with(filename, ".gtx")) {
+                // gtx files, from straight EPSG definition, must be applied in
+                // reverse order for "Geographic3D to GravityRelatedHeight"
+                // method
+                doInversion = !doInversion;
+            }
+            if (doInversion) {
                 formatter->startInversion();
             }
             formatter->addStep("vgridshift");
             formatter->addParam("grids", filename);
             formatter->addParam("multiplier", 1.0);
-            if (isMethodInverseOf) {
+            if (doInversion) {
                 formatter->stopInversion();
             }
             return;
diff --git a/src/iso19111/factory.cpp b/src/iso19111/factory.cpp
index b893faff..14421022 100644
--- a/src/iso19111/factory.cpp
+++ b/src/iso19111/factory.cpp
@@ -1024,8 +1024,8 @@ bool DatabaseContext::lookForGridInfo(const std::string &projFilename,
         info.url = url;
         info.directDownload = directDownload;
         info.openLicense = openLicense;
-        info.gridAvailable = gridAvailable;
     }
+    info.gridAvailable = gridAvailable;
     info.found = ret;
     d->cache(projFilename, info);
     return ret;