Add QgsCoordinateReferenceSystem::isDynamic()

Returns TRUE if the given proj coordinate system is a dynamic CRS. A dynamic CRS relies on a dynamic datum, that is a datum that is no plate-fixed.
qgis · May 10, 2021 · 9e7e0d4 · 9e7e0d4
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diff --git a/python/core/auto_generated/proj/qgscoordinatereferencesystem.sip.in b/python/core/auto_generated/proj/qgscoordinatereferencesystem.sip.in
@@ -791,6 +791,16 @@ overridden with these.
 Returns whether the CRS is a geographic CRS (using lat/lon coordinates)
 
 :return: ``True`` if CRS is geographic, or ``False`` if it is a projected CRS
+%End
+
+    bool isDynamic() const;
+%Docstring
+Returns ``True`` if the CRS is a dynamic CRS.
+
+A dynamic CRS relies on a dynamic datum, that is a datum that is not
+plate-fixed.
+
+.. versionadded:: 3.20
 %End
 
     QgsDatumEnsemble datumEnsemble() const throw( QgsNotSupportedException );

diff --git a/src/core/proj/qgscoordinatereferencesystem.cpp b/src/core/proj/qgscoordinatereferencesystem.cpp
@@ -1197,6 +1197,15 @@ bool QgsCoordinateReferenceSystem::isGeographic() const
   return d->mIsGeographic;
 }
 
+bool QgsCoordinateReferenceSystem::isDynamic() const
+{
+  const PJ *pj = projObject();
+  if ( !pj )
+    return false;
+
+  return QgsProjUtils::isDynamic( pj );
+}
+
 QgsDatumEnsemble QgsCoordinateReferenceSystem::datumEnsemble() const
 {
   QgsDatumEnsemble res;

diff --git a/src/core/proj/qgscoordinatereferencesystem.h b/src/core/proj/qgscoordinatereferencesystem.h
@@ -732,6 +732,16 @@ class CORE_EXPORT QgsCoordinateReferenceSystem
      */
     bool isGeographic() const;
 
+    /**
+     * Returns TRUE if the CRS is a dynamic CRS.
+     *
+     * A dynamic CRS relies on a dynamic datum, that is a datum that is not
+     * plate-fixed.
+     *
+     * \since QGIS 3.20
+     */
+    bool isDynamic() const;
+
     /**
      * Attempts to retrieve datum ensemble details from the CRS.
      *

diff --git a/src/core/proj/qgsprojutils.cpp b/src/core/proj/qgsprojutils.cpp
@@ -139,6 +139,48 @@ bool QgsProjUtils::axisOrderIsSwapped( const PJ *crs )
   return false;
 }
 
+bool QgsProjUtils::isDynamic( const PJ *crs )
+{
+  // ported from GDAL OGRSpatialReference::IsDynamic()
+  bool isDynamic = false;
+  PJ_CONTEXT *context = QgsProjContext::get();
+
+  proj_pj_unique_ptr horiz = crsToSingleCrs( crs );
+
+  proj_pj_unique_ptr datum( horiz ? proj_crs_get_datum( context, horiz.get() ) : nullptr );
+  if ( datum )
+  {
+    const PJ_TYPE type = proj_get_type( datum.get() );
+    isDynamic = type == PJ_TYPE_DYNAMIC_GEODETIC_REFERENCE_FRAME ||
+                type == PJ_TYPE_DYNAMIC_VERTICAL_REFERENCE_FRAME;
+    if ( !isDynamic )
+    {
+      const QString authName( proj_get_id_auth_name( datum.get(), 0 ) );
+      const QString code( proj_get_id_code( datum.get(), 0 ) );
+      if ( authName == QLatin1String( "EPSG" ) && code == QLatin1String( "6326" ) )
+      {
+        isDynamic = true;
+      }
+    }
+  }
+#if PROJ_VERSION_MAJOR > 7 || (PROJ_VERSION_MAJOR == 7 && PROJ_VERSION_MINOR >= 2)
+  else
+  {
+    proj_pj_unique_ptr ensemble( horiz ? proj_crs_get_datum_ensemble( context, horiz.get() ) : nullptr );
+    if ( ensemble )
+    {
+      proj_pj_unique_ptr member( proj_datum_ensemble_get_member( context, ensemble.get(), 0 ) );
+      if ( member )
+      {
+        const PJ_TYPE type = proj_get_type( member.get() );
+        isDynamic = type == PJ_TYPE_DYNAMIC_GEODETIC_REFERENCE_FRAME ||
+                    type == PJ_TYPE_DYNAMIC_VERTICAL_REFERENCE_FRAME;
+      }
+    }
+  }
+#endif
+  return isDynamic;
+}
 
 QgsProjUtils::proj_pj_unique_ptr QgsProjUtils::crsToSingleCrs( const PJ *crs )
 {

diff --git a/src/core/proj/qgsprojutils.h b/src/core/proj/qgsprojutils.h
@@ -147,6 +147,16 @@ class CORE_EXPORT QgsProjUtils
      */
     static bool axisOrderIsSwapped( const PJ *crs );
 
+    /**
+     * Returns TRUE if the given proj coordinate system is a dynamic CRS.
+     *
+     * A dynamic CRS relies on a dynamic datum, that is a datum that is not
+     * plate-fixed.
+     *
+     * \since QGIS 3.20
+     */
+    static bool isDynamic( const PJ *crs );
+
     /**
      * Given a PROJ crs (which may be a compound or bound crs, or some other type), extract a single crs
      * from it.

diff --git a/tests/src/core/testqgscoordinatereferencesystem.cpp b/tests/src/core/testqgscoordinatereferencesystem.cpp
@@ -77,6 +77,7 @@ class TestQgsCoordinateReferenceSystem: public QObject
     void toProj();
     void isGeographic();
     void mapUnits();
+    void isDynamic();
     void setValidationHint();
     void hasAxisInverted();
     void createFromProjInvalid();
@@ -1200,6 +1201,41 @@ void TestQgsCoordinateReferenceSystem::mapUnits()
   // an invalid crs should return unknown unit
   QCOMPARE( QgsCoordinateReferenceSystem().mapUnits(), QgsUnitTypes::DistanceUnknownUnit );
 }
+
+void TestQgsCoordinateReferenceSystem::isDynamic()
+{
+#if (PROJ_VERSION_MAJOR>7 || (PROJ_VERSION_MAJOR==7 && PROJ_VERSION_MINOR >= 2 ) )
+  QgsCoordinateReferenceSystem crs( QStringLiteral( "EPSG:7665" ) );
+  QVERIFY( crs.isDynamic() );
+
+  crs = QgsCoordinateReferenceSystem( QStringLiteral( "EPSG:4171" ) );
+  QVERIFY( !crs.isDynamic() );
+
+  // WGS84 (generic), using datum ensemble
+  crs = QgsCoordinateReferenceSystem( QStringLiteral( "EPSG:4326" ) );
+  QVERIFY( crs.isDynamic() );
+
+  // ETRS89 (generic), using datum ensemble
+  crs = QgsCoordinateReferenceSystem( QStringLiteral( "EPSG:4258" ) );
+  QVERIFY( !crs.isDynamic() );
+
+  QVERIFY( crs.createFromWkt( QStringLiteral( R"""(GEOGCS["WGS 84",
+      DATUM["WGS_1984",
+          SPHEROID["WGS 84",6378137,298.257223563,
+              AUTHORITY["EPSG","7030"]],
+          AUTHORITY["EPSG","6326"]],
+      PRIMEM["Greenwich",0,
+          AUTHORITY["EPSG","8901"]],
+      UNIT["degree",0.0174532925199433,
+          AUTHORITY["EPSG","9122"]],
+      AXIS["Latitude",NORTH],
+      AXIS["Longitude",EAST],
+      AUTHORITY["EPSG","4326"]])""" ) ) );
+  QVERIFY( crs.isValid() );
+  QVERIFY( crs.isDynamic() );
+#endif
+}
+
 void TestQgsCoordinateReferenceSystem::setValidationHint()
 {
   QgsCoordinateReferenceSystem myCrs;