CRS JSON: export GeographicCRS and Projected CRS

7 files changed, 541 insertions, 16 deletions

diff --git a/src/iso19111/common.cpp b/src/iso19111/common.cpp
index f2a51032..fb7a63c0 100644
--- a/src/iso19111/common.cpp
+++ b/src/iso19111/common.cpp
@@ -243,7 +243,9 @@ void UnitOfMeasure::_exportToJSON(
     JSONFormatter *formatter) const // throw(FormattingException)
 {
     auto &writer = formatter->writer();
-    PROJ::CPLJSonStreamingWriter::ObjectContext objContext(writer);
+    const auto &l_codeSpace = codeSpace();
+    auto objContext(
+        formatter->MakeObjectContext(nullptr, !l_codeSpace.empty()));
     writer.AddObjKey("type");
     const auto l_type = type();
     if (l_type == Type::LINEAR) {
@@ -268,10 +270,9 @@ void UnitOfMeasure::_exportToJSON(
     writer.AddObjKey("conversion_factor");
     writer.Add(factor, 15);
 
-    const auto &l_codeSpace = codeSpace();
     if (!l_codeSpace.empty() && formatter->outputId()) {
         writer.AddObjKey("id");
-        PROJ::CPLJSonStreamingWriter::ObjectContext idContext(writer);
+        auto idContext(formatter->MakeObjectContext(nullptr, false));
         writer.AddObjKey("authority");
         writer.Add(l_codeSpace);
         writer.AddObjKey("code");
@@ -871,7 +872,7 @@ void IdentifiedObject::formatID(JSONFormatter *formatter) const {
         ids.front()->_exportToJSON(formatter);
     } else if (!ids.empty()) {
         writer.AddObjKey("ids");
-        PROJ::CPLJSonStreamingWriter::ArrayContext arrayContext(writer);
+        auto arrayContext(writer.MakeArrayContext());
         for (const auto &id : ids) {
             id->_exportToJSON(formatter);
         }
@@ -880,6 +881,16 @@ void IdentifiedObject::formatID(JSONFormatter *formatter) const {
 
 // ---------------------------------------------------------------------------
 
+void IdentifiedObject::formatRemarks(JSONFormatter *formatter) const {
+    if (!remarks().empty()) {
+        auto &writer = formatter->writer();
+        writer.AddObjKey("remarks");
+        writer.Add(remarks());
+    }
+}
+
+// ---------------------------------------------------------------------------
+
 bool IdentifiedObject::_isEquivalentTo(
     const util::IComparable *other,
     util::IComparable::Criterion criterion) const {
@@ -1031,6 +1042,46 @@ void ObjectDomain::_exportToWKT(WKTFormatter *formatter) const {
 // ---------------------------------------------------------------------------
 
 //! @cond Doxygen_Suppress
+void ObjectDomain::_exportToJSON(JSONFormatter *formatter) const {
+    auto &writer = formatter->writer();
+    if (d->scope_.has_value()) {
+        writer.AddObjKey("scope");
+        writer.Add(*(d->scope_));
+    }
+    if (d->domainOfValidity_) {
+        if (d->domainOfValidity_->description().has_value()) {
+            writer.AddObjKey("area");
+            writer.Add(*(d->domainOfValidity_->description()));
+        }
+        if (d->domainOfValidity_->geographicElements().size() == 1) {
+            const auto bbox = dynamic_cast<const GeographicBoundingBox *>(
+                d->domainOfValidity_->geographicElements()[0].get());
+            if (bbox) {
+                writer.AddObjKey("bbox");
+                auto bboxContext(writer.MakeObjectContext());
+                writer.AddObjKey("south_latitude");
+                writer.Add(bbox->southBoundLatitude(), 15);
+                writer.AddObjKey("west_longitude");
+                writer.Add(bbox->westBoundLongitude(), 15);
+                writer.AddObjKey("north_latitude");
+                writer.Add(bbox->northBoundLatitude(), 15);
+                writer.AddObjKey("east_longitude");
+                writer.Add(bbox->eastBoundLongitude(), 15);
+            }
+        }
+        if (d->domainOfValidity_->verticalElements().size() == 1) {
+            // TODO
+        }
+        if (d->domainOfValidity_->temporalElements().size() == 1) {
+            // TODO
+        }
+    }
+}
+//! @endcond
+
+// ---------------------------------------------------------------------------
+
+//! @cond Doxygen_Suppress
 bool ObjectDomain::_isEquivalentTo(
     const util::IComparable *other,
     util::IComparable::Criterion criterion) const {
@@ -1162,6 +1213,31 @@ void ObjectUsage::baseExportToWKT(WKTFormatter *formatter) const {
 
 // ---------------------------------------------------------------------------
 
+void ObjectUsage::baseExportToJSON(JSONFormatter *formatter) const {
+
+    auto &writer = formatter->writer();
+    if (formatter->outputUsage()) {
+        const auto &l_domains = domains();
+        if (l_domains.size() == 1) {
+            l_domains[0]->_exportToJSON(formatter);
+        } else if (!l_domains.empty()) {
+            writer.AddObjKey("usages");
+            auto arrayContext(writer.MakeArrayContext(false));
+            for (const auto &domain : l_domains) {
+                auto objContext(writer.MakeObjectContext());
+                domain->_exportToJSON(formatter);
+            }
+        }
+    }
+
+    if (formatter->outputId()) {
+        formatID(formatter);
+    }
+    formatRemarks(formatter);
+}
+
+// ---------------------------------------------------------------------------
+
 //! @cond Doxygen_Suppress
 bool ObjectUsage::_isEquivalentTo(
     const util::IComparable *other,
diff --git a/src/iso19111/coordinateoperation.cpp b/src/iso19111/coordinateoperation.cpp
index 7f3a2137..a2a31edd 100644
--- a/src/iso19111/coordinateoperation.cpp
+++ b/src/iso19111/coordinateoperation.cpp
@@ -991,6 +991,24 @@ void OperationMethod::_exportToWKT(io::WKTFormatter *formatter) const {
 // ---------------------------------------------------------------------------
 
 //! @cond Doxygen_Suppress
+void OperationMethod::_exportToJSON(
+    io::JSONFormatter *formatter) const // throw(FormattingException)
+{
+    auto &writer = formatter->writer();
+    auto objectContext(formatter->MakeObjectContext("OperationMethod",
+                                                    !identifiers().empty()));
+
+    writer.AddObjKey("name");
+    writer.Add(nameStr());
+
+    if (formatter->outputId()) {
+        formatID(formatter);
+    }
+}
+
+// ---------------------------------------------------------------------------
+
+//! @cond Doxygen_Suppress
 bool OperationMethod::_isEquivalentTo(
     const util::IComparable *other,
     util::IComparable::Criterion criterion) const {
@@ -1168,6 +1186,35 @@ void OperationParameterValue::_exportToWKT(io::WKTFormatter *formatter,
 // ---------------------------------------------------------------------------
 
 //! @cond Doxygen_Suppress
+void OperationParameterValue::_exportToJSON(
+    io::JSONFormatter *formatter) const {
+    auto &writer = formatter->writer();
+    auto objectContext(formatter->MakeObjectContext(
+        "ParameterValue", !parameter()->identifiers().empty()));
+
+    writer.AddObjKey("name");
+    writer.Add(parameter()->nameStr());
+
+    const auto &l_value(parameterValue());
+    if (l_value->type() == ParameterValue::Type::MEASURE) {
+        writer.AddObjKey("value");
+        writer.Add(l_value->value().value(), 15);
+        writer.AddObjKey("unit");
+        l_value->value().unit()._exportToJSON(formatter);
+    } else if (l_value->type() == ParameterValue::Type::FILENAME) {
+        writer.AddObjKey("value");
+        writer.Add(l_value->valueFile());
+    }
+
+    if (formatter->outputId()) {
+        parameter()->formatID(formatter);
+    }
+}
+//! @endcond
+
+// ---------------------------------------------------------------------------
+
+//! @cond Doxygen_Suppress
 
 /** Utility method used on WKT2 import to convert from abridged transformation
  * to "normal" transformation parameters.
@@ -5410,6 +5457,44 @@ void Conversion::_exportToWKT(io::WKTFormatter *formatter) const {
 // ---------------------------------------------------------------------------
 
 //! @cond Doxygen_Suppress
+void Conversion::_exportToJSON(
+    io::JSONFormatter *formatter) const // throw(FormattingException)
+{
+    auto &writer = formatter->writer();
+    auto objectContext(
+        formatter->MakeObjectContext("Conversion", !identifiers().empty()));
+
+    writer.AddObjKey("name");
+    auto l_name = nameStr();
+    if (l_name.empty()) {
+        writer.Add("unnamed");
+    } else {
+        writer.Add(l_name);
+    }
+
+    writer.AddObjKey("method");
+    formatter->setAllowIDInImmediateChild();
+    method()->_exportToJSON(formatter);
+
+    writer.AddObjKey("parameters");
+    {
+        auto parametersContext(writer.MakeArrayContext(false));
+        for (const auto &genOpParamvalue : parameterValues()) {
+            formatter->setAllowIDInImmediateChild();
+            genOpParamvalue->_exportToJSON(formatter);
+        }
+    }
+
+    if (formatter->outputId()) {
+        formatID(formatter);
+    }
+}
+
+//! @endcond
+
+// ---------------------------------------------------------------------------
+
+//! @cond Doxygen_Suppress
 static bool createPROJ4WebMercator(const Conversion *conv,
                                    io::PROJStringFormatter *formatter) {
     const double centralMeridian = conv->parameterValueNumeric(
diff --git a/src/iso19111/coordinatesystem.cpp b/src/iso19111/coordinatesystem.cpp
index ef9cac93..f96a962f 100644
--- a/src/iso19111/coordinatesystem.cpp
+++ b/src/iso19111/coordinatesystem.cpp
@@ -311,8 +311,8 @@ void CoordinateSystemAxis::_exportToWKT(io::WKTFormatter *formatter, int order,
                                         bool disableAbbrev) const {
     const bool isWKT2 = formatter->version() == io::WKTFormatter::Version::WKT2;
     formatter->startNode(io::WKTConstants::AXIS, !identifiers().empty());
-    std::string axisName = *(name()->description());
-    std::string abbrev = abbreviation();
+    const std::string &axisName = nameStr();
+    const std::string &abbrev = abbreviation();
     std::string parenthesizedAbbrev = "(" + abbrev + ")";
     std::string dir = direction().toString();
     std::string axisDesignation;
@@ -393,6 +393,34 @@ void CoordinateSystemAxis::_exportToWKT(io::WKTFormatter *formatter, int order,
 // ---------------------------------------------------------------------------
 
 //! @cond Doxygen_Suppress
+void CoordinateSystemAxis::_exportToJSON(
+    io::JSONFormatter *formatter) const // throw(FormattingException)
+{
+    auto &writer = formatter->writer();
+    auto objectContext(
+        formatter->MakeObjectContext("Axis", !identifiers().empty()));
+
+    writer.AddObjKey("name");
+    writer.Add(nameStr());
+
+    writer.AddObjKey("abbreviation");
+    writer.Add(abbreviation());
+
+    writer.AddObjKey("direction");
+    writer.Add(direction().toString());
+
+    writer.AddObjKey("unit");
+    unit()._exportToJSON(formatter);
+
+    if (formatter->outputId()) {
+        formatID(formatter);
+    }
+}
+//! @endcond
+
+// ---------------------------------------------------------------------------
+
+//! @cond Doxygen_Suppress
 bool CoordinateSystemAxis::_isEquivalentTo(
     const util::IComparable *other,
     util::IComparable::Criterion criterion) const {
@@ -535,6 +563,33 @@ void CoordinateSystem::_exportToWKT(
 // ---------------------------------------------------------------------------
 
 //! @cond Doxygen_Suppress
+void CoordinateSystem::_exportToJSON(
+    io::JSONFormatter *formatter) const // throw(FormattingException)
+{
+    auto &writer = formatter->writer();
+    auto objectContext(formatter->MakeObjectContext("CoordinateSystem",
+                                                    !identifiers().empty()));
+
+    writer.AddObjKey("subtype");
+    writer.Add(getWKT2Type(true));
+
+    writer.AddObjKey("axis");
+    auto axisContext(writer.MakeArrayContext(false));
+    const auto &l_axisList = axisList();
+    for (auto &axis : l_axisList) {
+        axis->_exportToJSON(formatter);
+    }
+
+    if (formatter->outputId()) {
+        formatID(formatter);
+    }
+}
+
+//! @endcond
+
+// ---------------------------------------------------------------------------
+
+//! @cond Doxygen_Suppress
 bool CoordinateSystem::_isEquivalentTo(
     const util::IComparable *other,
     util::IComparable::Criterion criterion) const {
diff --git a/src/iso19111/crs.cpp b/src/iso19111/crs.cpp
index 476bc72b..2ca2786d 100644
--- a/src/iso19111/crs.cpp
+++ b/src/iso19111/crs.cpp
@@ -1342,6 +1342,39 @@ void GeodeticCRS::addDatumInfoToPROJString(
 // ---------------------------------------------------------------------------
 
 //! @cond Doxygen_Suppress
+void GeodeticCRS::_exportToJSON(
+    io::JSONFormatter *formatter) const // throw(io::FormattingException)
+{
+    auto &writer = formatter->writer();
+    auto objectContext(
+        formatter->MakeObjectContext("GeodeticCRS", !identifiers().empty()));
+
+    writer.AddObjKey("name");
+    auto l_name = nameStr();
+    if (l_name.empty()) {
+        writer.Add("unnamed");
+    } else {
+        writer.Add(l_name);
+    }
+
+    const auto &l_datum(datum());
+    if (l_datum) {
+        writer.AddObjKey("datum");
+        l_datum->_exportToJSON(formatter);
+    } else {
+        // TODO DatumEnsemble
+    }
+
+    writer.AddObjKey("coordinate_system");
+    coordinateSystem()->_exportToJSON(formatter);
+
+    ObjectUsage::baseExportToJSON(formatter);
+}
+//! @endcond
+
+// ---------------------------------------------------------------------------
+
+//! @cond Doxygen_Suppress
 static util::IComparable::Criterion
 getStandardCriterion(util::IComparable::Criterion criterion) {
     return criterion == util::IComparable::Criterion::
@@ -2059,6 +2092,39 @@ void GeographicCRS::_exportToPROJString(
 // ---------------------------------------------------------------------------
 
 //! @cond Doxygen_Suppress
+void GeographicCRS::_exportToJSON(
+    io::JSONFormatter *formatter) const // throw(io::FormattingException)
+{
+    auto &writer = formatter->writer();
+    auto objectContext(
+        formatter->MakeObjectContext("GeographicCRS", !identifiers().empty()));
+
+    writer.AddObjKey("name");
+    auto l_name = nameStr();
+    if (l_name.empty()) {
+        writer.Add("unnamed");
+    } else {
+        writer.Add(l_name);
+    }
+
+    const auto &l_datum(datum());
+    if (l_datum) {
+        writer.AddObjKey("datum");
+        l_datum->_exportToJSON(formatter);
+    } else {
+        // TODO DatumEnsemble
+    }
+
+    writer.AddObjKey("coordinate_system");
+    coordinateSystem()->_exportToJSON(formatter);
+
+    ObjectUsage::baseExportToJSON(formatter);
+}
+//! @endcond
+
+// ---------------------------------------------------------------------------
+
+//! @cond Doxygen_Suppress
 struct VerticalCRS::Private {
     std::vector<operation::TransformationNNPtr> geoidModel{};
     std::vector<operation::PointMotionOperationNNPtr> velocityModel{};
@@ -2856,6 +2922,38 @@ void ProjectedCRS::_exportToWKT(io::WKTFormatter *formatter) const {
 
 // ---------------------------------------------------------------------------
 
+//! @cond Doxygen_Suppress
+void ProjectedCRS::_exportToJSON(
+    io::JSONFormatter *formatter) const // throw(io::FormattingException)
+{
+    auto &writer = formatter->writer();
+    auto objectContext(
+        formatter->MakeObjectContext("ProjectedCRS", !identifiers().empty()));
+
+    writer.AddObjKey("name");
+    auto l_name = nameStr();
+    if (l_name.empty()) {
+        writer.Add("unnamed");
+    } else {
+        writer.Add(l_name);
+    }
+
+    writer.AddObjKey("base_crs");
+    formatter->setAllowIDInImmediateChild();
+    baseCRS()->_exportToJSON(formatter);
+
+    writer.AddObjKey("conversion");
+    derivingConversionRef()->_exportToJSON(formatter);
+
+    writer.AddObjKey("coordinate_system");
+    coordinateSystem()->_exportToJSON(formatter);
+
+    ObjectUsage::baseExportToJSON(formatter);
+}
+//! @endcond
+
+// ---------------------------------------------------------------------------
+
 void ProjectedCRS::_exportToPROJString(
     io::PROJStringFormatter *formatter) const // throw(io::FormattingException)
 {
@@ -4195,6 +4293,37 @@ void DerivedGeodeticCRS::_exportToWKT(io::WKTFormatter *formatter) const {
 
 // ---------------------------------------------------------------------------
 
+//! @cond Doxygen_Suppress
+void DerivedGeodeticCRS::_exportToJSON(
+    io::JSONFormatter *formatter) const // throw(io::FormattingException)
+{
+    auto &writer = formatter->writer();
+    auto objectContext(formatter->MakeObjectContext("DerivedGeodeticCRS",
+                                                    !identifiers().empty()));
+
+    writer.AddObjKey("name");
+    auto l_name = nameStr();
+    if (l_name.empty()) {
+        writer.Add("unnamed");
+    } else {
+        writer.Add(l_name);
+    }
+
+    writer.AddObjKey("base_crs");
+    baseCRS()->_exportToJSON(formatter);
+
+    writer.AddObjKey("conversion");
+    derivingConversionRef()->_exportToJSON(formatter);
+
+    writer.AddObjKey("coordinate_system");
+    coordinateSystem()->_exportToJSON(formatter);
+
+    ObjectUsage::baseExportToJSON(formatter);
+}
+//! @endcond
+
+// ---------------------------------------------------------------------------
+
 void DerivedGeodeticCRS::_exportToPROJString(
     io::PROJStringFormatter *) const // throw(io::FormattingException)
 {
@@ -4333,6 +4462,37 @@ void DerivedGeographicCRS::_exportToWKT(io::WKTFormatter *formatter) const {
 
 // ---------------------------------------------------------------------------
 
+//! @cond Doxygen_Suppress
+void DerivedGeographicCRS::_exportToJSON(
+    io::JSONFormatter *formatter) const // throw(io::FormattingException)
+{
+    auto &writer = formatter->writer();
+    auto objectContext(formatter->MakeObjectContext("DerivedGeographicCRS",
+                                                    !identifiers().empty()));
+
+    writer.AddObjKey("name");
+    auto l_name = nameStr();
+    if (l_name.empty()) {
+        writer.Add("unnamed");
+    } else {
+        writer.Add(l_name);
+    }
+
+    writer.AddObjKey("base_crs");
+    baseCRS()->_exportToJSON(formatter);
+
+    writer.AddObjKey("conversion");
+    derivingConversionRef()->_exportToJSON(formatter);
+
+    writer.AddObjKey("coordinate_system");
+    coordinateSystem()->_exportToJSON(formatter);
+
+    ObjectUsage::baseExportToJSON(formatter);
+}
+//! @endcond
+
+// ---------------------------------------------------------------------------
+
 void DerivedGeographicCRS::_exportToPROJString(
     io::PROJStringFormatter *) const // throw(io::FormattingException)
 {
diff --git a/src/iso19111/datum.cpp b/src/iso19111/datum.cpp
index 6ba219d4..89ecc755 100644
--- a/src/iso19111/datum.cpp
+++ b/src/iso19111/datum.cpp
@@ -93,6 +93,9 @@ struct Datum::Private {
 
     // cppcheck-suppress functionStatic
     void exportAnchorDefinition(io::WKTFormatter *formatter) const;
+
+    // cppcheck-suppress functionStatic
+    void exportAnchorDefinition(io::JSONFormatter *formatter) const;
 };
 
 // ---------------------------------------------------------------------------
@@ -105,6 +108,17 @@ void Datum::Private::exportAnchorDefinition(io::WKTFormatter *formatter) const {
     }
 }
 
+// ---------------------------------------------------------------------------
+
+void Datum::Private::exportAnchorDefinition(
+    io::JSONFormatter *formatter) const {
+    if (anchorDefinition) {
+        auto &writer = formatter->writer();
+        writer.AddObjKey("anchor");
+        writer.Add(*anchorDefinition);
+    }
+}
+
 //! @endcond
 
 // ---------------------------------------------------------------------------
@@ -352,10 +366,8 @@ void PrimeMeridian::_exportToJSON(
     io::JSONFormatter *formatter) const // throw(FormattingException)
 {
     auto &writer = formatter->writer();
-    PROJ::CPLJSonStreamingWriter::ObjectContext objectContext(writer);
-
-    writer.AddObjKey("type");
-    writer.Add("PrimeMeridian");
+    auto objectContext(
+        formatter->MakeObjectContext("PrimeMeridian", !identifiers().empty()));
 
     writer.AddObjKey("name");
     std::string l_name =
@@ -365,7 +377,7 @@ void PrimeMeridian::_exportToJSON(
     const auto &l_long = longitude();
     writer.AddObjKey("longitude");
     {
-        PROJ::CPLJSonStreamingWriter::ObjectContext longitudeContext(writer);
+        auto longitudeContext(formatter->MakeObjectContext(nullptr, false));
         writer.AddObjKey("value");
         writer.Add(l_long.value(), 15);
 
@@ -803,6 +815,60 @@ void Ellipsoid::_exportToWKT(
 
 // ---------------------------------------------------------------------------
 
+//! @cond Doxygen_Suppress
+void Ellipsoid::_exportToJSON(
+    io::JSONFormatter *formatter) const // throw(FormattingException)
+{
+    auto &writer = formatter->writer();
+    auto objectContext(
+        formatter->MakeObjectContext("Ellipsoid", !identifiers().empty()));
+
+    writer.AddObjKey("name");
+    auto l_name = nameStr();
+    if (l_name.empty()) {
+        writer.Add("unnamed");
+    } else {
+        writer.Add(l_name);
+    }
+
+    const auto &semiMajor = semiMajorAxis();
+    const auto &semiMajorUnit = semiMajor.unit();
+    writer.AddObjKey(isSphere() ? "radius" : "semi_major_axis");
+    {
+        auto objContext(formatter->MakeObjectContext(nullptr, false));
+        writer.AddObjKey("value");
+        writer.Add(semiMajor.value(), 15);
+
+        writer.AddObjKey("unit");
+        semiMajorUnit._exportToJSON(formatter);
+    }
+
+    if (!isSphere()) {
+        const auto &l_inverseFlattening = inverseFlattening();
+        if (l_inverseFlattening.has_value()) {
+            writer.AddObjKey("inverse_flattening");
+            writer.Add(l_inverseFlattening->getSIValue(), 15);
+        } else {
+            writer.AddObjKey("semi_minor_axis");
+            {
+                auto objContext(formatter->MakeObjectContext(nullptr, false));
+                writer.AddObjKey("value");
+                writer.Add(semiMinorAxis()->value(), 15);
+
+                writer.AddObjKey("unit");
+                semiMinorAxis()->unit()._exportToJSON(formatter);
+            }
+        }
+    }
+
+    if (formatter->outputId()) {
+        formatID(formatter);
+    }
+}
+//! @endcond
+
+// ---------------------------------------------------------------------------
+
 bool Ellipsoid::lookForProjWellKnownEllps(std::string &projEllpsName,
                                           std::string &ellpsName) const {
     const double a = semiMajorAxis().getSIValue();
@@ -1188,6 +1254,36 @@ void GeodeticReferenceFrame::_exportToWKT(
 // ---------------------------------------------------------------------------
 
 //! @cond Doxygen_Suppress
+void GeodeticReferenceFrame::_exportToJSON(
+    io::JSONFormatter *formatter) const // throw(FormattingException)
+{
+    auto objectContext(formatter->MakeObjectContext("GeodeticReferenceFrame",
+                                                    !identifiers().empty()));
+    auto &writer = formatter->writer();
+
+    writer.AddObjKey("name");
+    auto l_name = nameStr();
+    if (l_name.empty()) {
+        writer.Add("unnamed");
+    } else {
+        writer.Add(l_name);
+    }
+
+    Datum::getPrivate()->exportAnchorDefinition(formatter);
+
+    writer.AddObjKey("ellipsoid");
+    ellipsoid()->_exportToJSON(formatter);
+
+    writer.AddObjKey("prime_meridian");
+    primeMeridian()->_exportToJSON(formatter);
+
+    ObjectUsage::baseExportToJSON(formatter);
+}
+//! @endcond
+
+// ---------------------------------------------------------------------------
+
+//! @cond Doxygen_Suppress
 bool GeodeticReferenceFrame::_isEquivalentTo(
     const util::IComparable *other,
     util::IComparable::Criterion criterion) const {
diff --git a/src/iso19111/io.cpp b/src/iso19111/io.cpp
index 0c9f8a0c..35798d9d 100644
--- a/src/iso19111/io.cpp
+++ b/src/iso19111/io.cpp
@@ -8021,9 +8021,20 @@ PROJStringParser::createFromPROJString(const std::string &projString) {
 
 //! @cond Doxygen_Suppress
 struct JSONFormatter::Private {
-    PROJ::CPLJSonStreamingWriter writer_{nullptr, nullptr};
+    CPLJSonStreamingWriter writer_{nullptr, nullptr};
     DatabaseContextPtr dbContext_{};
+
+    std::vector<bool> stackHasId_{false};
+    std::vector<bool> outputIdStack_{true};
+    bool allowIDInImmediateChild_ = false;
+
     std::string result_{};
+
+    // cppcheck-suppress functionStatic
+    void pushOutputId(bool outputIdIn) { outputIdStack_.push_back(outputIdIn); }
+
+    // cppcheck-suppress functionStatic
+    void popOutputId() { outputIdStack_.pop_back(); }
 };
 //! @endcond
 
@@ -8071,13 +8082,55 @@ JSONFormatter::~JSONFormatter() = default;
 
 // ---------------------------------------------------------------------------
 
-PROJ::CPLJSonStreamingWriter &JSONFormatter::writer() const {
-    return d->writer_;
+CPLJSonStreamingWriter &JSONFormatter::writer() const { return d->writer_; }
+
+// ---------------------------------------------------------------------------
+
+bool JSONFormatter::outputId() const { return d->outputIdStack_.back(); }
+
+// ---------------------------------------------------------------------------
+
+bool JSONFormatter::outputUsage() const {
+    return outputId() && d->outputIdStack_.size() == 2;
 }
 
 // ---------------------------------------------------------------------------
 
-bool JSONFormatter::outputId() const { return true; }
+void JSONFormatter::setAllowIDInImmediateChild() {
+    d->allowIDInImmediateChild_ = true;
+}
+
+// ---------------------------------------------------------------------------
+
+JSONFormatter::ObjectContext::ObjectContext(JSONFormatter &formatter,
+                                            const char *objectType, bool hasId)
+    : m_formatter(formatter) {
+    m_formatter.d->writer_.StartObj();
+    if (objectType) {
+        m_formatter.d->writer_.AddObjKey("type");
+        m_formatter.d->writer_.Add(objectType);
+    }
+    // All intermediate nodes shouldn't have ID if a parent has an ID
+    // unless explicitly enabled.
+    if (m_formatter.d->allowIDInImmediateChild_) {
+        m_formatter.d->pushOutputId(m_formatter.d->outputIdStack_[0]);
+        m_formatter.d->allowIDInImmediateChild_ = false;
+    } else {
+        m_formatter.d->pushOutputId(m_formatter.d->outputIdStack_[0] &&
+                                    !m_formatter.d->stackHasId_.back());
+    }
+
+    m_formatter.d->stackHasId_.push_back(hasId ||
+                                         m_formatter.d->stackHasId_.back());
+}
+
+// ---------------------------------------------------------------------------
+
+JSONFormatter::ObjectContext::~ObjectContext() {
+    m_formatter.d->writer_.EndObj();
+    m_formatter.d->stackHasId_.pop_back();
+    m_formatter.d->popOutputId();
+}
 
 //! @endcond
 
diff --git a/src/iso19111/metadata.cpp b/src/iso19111/metadata.cpp
index 761b909b..41653b32 100644
--- a/src/iso19111/metadata.cpp
+++ b/src/iso19111/metadata.cpp
@@ -1096,7 +1096,7 @@ void Identifier::_exportToJSON(JSONFormatter *formatter) const {
     const std::string &l_codeSpace = *codeSpace();
     if (!l_codeSpace.empty() && !l_code.empty()) {
         auto &writer = formatter->writer();
-        PROJ::CPLJSonStreamingWriter::ObjectContext objContext(writer);
+        auto objContext(formatter->MakeObjectContext(nullptr, false));
         writer.AddObjKey("authority");
         writer.Add(l_codeSpace);
         writer.AddObjKey("code");