import/export PROJJSON: support a interpolation_crs key to geoid_model for faithful serialization of the geoid_geog_crs parameter of proj_create_vertical_crs_ex()

1 files changed, 9 insertions, 0 deletions

diff --git a/src/iso19111/crs.cpp b/src/iso19111/crs.cpp
index a55b701a..cf533bd3 100644
--- a/src/iso19111/crs.cpp
+++ b/src/iso19111/crs.cpp
@@ -2584,6 +2584,15 @@ void VerticalCRS::_exportToJSON(
         auto objectContext2(formatter->MakeObjectContext(nullptr, false));
         writer.AddObjKey("name");
         writer.Add(model->nameStr());
+
+        if (model->identifiers().empty()) {
+            const auto &interpCRS = model->interpolationCRS();
+            if (interpCRS) {
+                writer.AddObjKey("interpolation_crs");
+                interpCRS->_exportToJSON(formatter);
+            }
+        }
+
         model->formatID(formatter);
     }