diff --git a/ugbase/bridge/disc_bridges/algebra_bridge.cpp b/ugbase/bridge/disc_bridges/algebra_bridge.cpp
index c13faa218..87c9a32a7 100644
--- a/ugbase/bridge/disc_bridges/algebra_bridge.cpp
+++ b/ugbase/bridge/disc_bridges/algebra_bridge.cpp
@@ -549,6 +549,9 @@ static void DomainAlgebra(Registry& reg, string parentGroup)
 							.add_method("enable_adaptive_refinement", &T::enable_adaptive_refinement)
 							.add_method("disable_adaptive_refinement", &T::disable_adaptive_refinement)
 							.add_method("config_string", &T::config_string)
+
+							.add_method("set_associated_space", &T::set_associated_space)
+							.add_method("set_absolute_tolerance", &T::set_absolute_tolerance)
 							.set_construct_as_smart_pointer(true);
 		reg.add_class_to_group(name, "NestedIterationSolver", tag);
 	}
diff --git a/ugbase/lib_disc/operator/linear_operator/nested_iteration/nested_iteration.h b/ugbase/lib_disc/operator/linear_operator/nested_iteration/nested_iteration.h
index 275df9eec..244fa6e41 100644
--- a/ugbase/lib_disc/operator/linear_operator/nested_iteration/nested_iteration.h
+++ b/ugbase/lib_disc/operator/linear_operator/nested_iteration/nested_iteration.h
@@ -46,6 +46,7 @@
 #include "lib_disc/assemble_interface.h"
 
 #include "lib_disc/spatial_disc/domain_disc.h"
+#include "lib_disc/function_spaces/metric_spaces.h"
 #include "lib_disc/function_spaces/error_elem_marking_strategy.h"
 
 #include "lib_algebra/operator/debug_writer.h"
@@ -138,7 +139,13 @@ class NestedIterationSolver
 	//! set marking strategy
 		void set_refinement_marking(SmartPtr<IElementMarkingStrategy<TDomain> > m) {m_spRefinementMarking =m; }
 		void set_coarsening_marking(SmartPtr<IElementMarkingStrategy<TDomain> > m) {m_spCoarseningMarking =m; }
-		void set_tolerance(number tol) {m_TOL = tol;}
+		void set_tolerance(number tol)
+		{
+			m_TOL = tol;
+			UG_LOG("NI::set_tolerance" << m_TOL <<std::endl);
+		}
+
+
 
 	//! indicates, if grids should be refined further (if desired accuracy has not been achieved)
 		bool use_adaptive_refinement() const {return m_bUseAdaptiveRefinement;}
@@ -150,6 +157,17 @@ class NestedIterationSolver
 
 		void set_max_steps(int steps) {m_maxSteps = steps;}
 		number last_error() const {return m_lastError;}
+
+		void set_associated_space(SmartPtr<IGridFunctionSpace<grid_function_type> > spSpace)
+		{ m_spAssociatedSpace = spSpace;}
+
+		void set_absolute_tolerance(number atol)
+		{
+
+			m_absTOL = atol;
+			UG_LOG("NI::set_absolute_tolerance" << m_absTOL <<std::endl);
+		}
+
 	///@}
 
 	/// for debug output
@@ -159,7 +177,7 @@ class NestedIterationSolver
 		{m_spElemError = spErrEta;}
 
 	protected:
-		//number estimate_error(const grid_function_type& u);
+		void estimate_and_mark_domain(const grid_function_type& u, SmartPtr<IElementMarkingStrategy<TDomain> > spMarking,  bool bClearMarks = true);
 		number refine_domain(const grid_function_type& u);
 		number coarsen_domain(const grid_function_type& u);
 
@@ -191,10 +209,18 @@ class NestedIterationSolver
 		SmartPtr<IElementMarkingStrategy<TDomain> > m_spCoarseningMarking;
 		bool m_bUseAdaptiveRefinement;
 
-		number m_TOL;
 		int m_maxSteps;
 		number m_lastError;
 
+	/// tolerance
+		number m_TOL;
+
+	/// associated norm (for relative error)
+		SmartPtr<IGridFunctionSpace<grid_function_type> > m_spAssociatedSpace;
+
+	/// absolute tolerance (for relative error)
+		number m_absTOL;
+
 	/// (optional) debug info for adaptive refinement
 		SmartPtr<grid_function_type> m_spElemError;
 
diff --git a/ugbase/lib_disc/operator/linear_operator/nested_iteration/nested_iteration_impl.h b/ugbase/lib_disc/operator/linear_operator/nested_iteration/nested_iteration_impl.h
index 1ae4ce08d..875fea665 100644
--- a/ugbase/lib_disc/operator/linear_operator/nested_iteration/nested_iteration_impl.h
+++ b/ugbase/lib_disc/operator/linear_operator/nested_iteration/nested_iteration_impl.h
@@ -62,7 +62,7 @@ NestedIterationSolver(SmartPtr<ILinearOperatorInverse<vector_type> > LinearSolve
 			m_spAss(NULL),
 			m_dgbCall(0),
 			m_lastNumSteps(0),
-			m_bUseAdaptiveRefinement(true)
+			m_bUseAdaptiveRefinement(true), m_TOL(1e-3), m_absTOL(1e-12), m_maxSteps(100)
 {};
 
 template <typename TDomain, typename TAlgebra>
@@ -74,7 +74,8 @@ NestedIterationSolver() :
 	m_spAss(NULL),
 	m_dgbCall(0),
 	m_lastNumSteps(0),
-	m_bUseAdaptiveRefinement(true)
+	m_bUseAdaptiveRefinement(true),
+	m_TOL(1e-3), m_absTOL(1e-12), m_maxSteps(100)
 {};
 
 template <typename TDomain, typename TAlgebra>
@@ -86,7 +87,7 @@ NestedIterationSolver(SmartPtr<IOperator<vector_type> > N) :
 	m_spAss(NULL),
 	m_dgbCall(0),
 	m_lastNumSteps(0),
-	m_bUseAdaptiveRefinement(true)
+	m_bUseAdaptiveRefinement(true),	m_TOL(1e-3), m_absTOL(1e-12), m_maxSteps(100)
 {
 	init(N);
 };
@@ -102,7 +103,7 @@ NestedIterationSolver(SmartPtr<IAssemble<TAlgebra> > spAss) :
 	m_dgbCall(0),
 	m_lastNumSteps(0),
 	m_baseLevel(0),
-	m_bUseAdaptiveRefinement(true)
+	m_bUseAdaptiveRefinement(true),	m_TOL(1e-3), m_absTOL(1e-12), m_maxSteps(100)
 {
 	m_N = SmartPtr<AssembledOperator<TAlgebra> >(new AssembledOperator<TAlgebra>(m_spAss));
 };
@@ -150,12 +151,12 @@ bool NestedIterationSolver<TDomain,TAlgebra>::prepare(vector_type& u)
 //! Refines domain and provides error estimate.
 /*! Values depend on m_spDomErr */
 template <typename TDomain, typename TAlgebra>
-number NestedIterationSolver<TDomain,TAlgebra>::refine_domain(const grid_function_type& u)
+void NestedIterationSolver<TDomain,TAlgebra>::estimate_and_mark_domain(const grid_function_type& u, SmartPtr<IElementMarkingStrategy<TDomain> > spMarking, bool bClearMarks)
 {
 	  UG_LOG("Computing error... "<< std::endl);
 
 	  typedef DomainDiscretization<TDomain, TAlgebra> domain_disc_type;
-	//  typedef IDomainErrorIndicator<TAlgebra> domain_indicator_type;
+	 //  typedef IDomainErrorIndicator<TAlgebra> domain_indicator_type;
 
 	  SmartPtr<domain_disc_type> spDomainEstimator = m_spDomErr.template cast_dynamic<domain_disc_type>();
 
@@ -165,19 +166,21 @@ number NestedIterationSolver<TDomain,TAlgebra>::refine_domain(const grid_functio
 
 	  // compute error
 	  if (m_spElemError.valid()) {
+		  // debug version
 		  spDomainEstimator->calc_error(u, u.dd(), &(*m_spElemError));
 	  } else {
+		  // standard version
 		  spDomainEstimator->calc_error(u, u.dd());
 	  }
+
 	  // set (new) marks
-	  m_spRefiner->clear_marks();
-	  spDomainEstimator->mark_with_strategy(*m_spRefiner, m_spRefinementMarking);
-	  UG_LOG("Estimated error: " << m_spRefinementMarking->global_estimated_error());
+	  if (bClearMarks) m_spRefiner->clear_marks();
+	  spDomainEstimator->mark_with_strategy(*m_spRefiner, spMarking);
+	  UG_LOG("Estimated error: " << spMarking->global_estimated_error());
+
+
 
-	  const number err = m_spRefinementMarking->global_estimated_error();
-	  if(err >= m_TOL) {m_spRefiner->refine();}
 
-	  return err;
 }
 
 
@@ -286,14 +289,14 @@ bool NestedIterationSolver<TDomain,TAlgebra>::apply(vector_type& u)
 
 		// Solve linearized system.
 		try{
-		NESTED_ITER_PROFILE_BEGIN(NewtonApplyLinSolver);
-		if(!m_spLinearSolver->apply(u, *spD))
-		{
-			UG_LOG("ERROR in 'NestedIterationSolver::apply': Cannot apply Inverse Linear "
-					"Operator for Jacobi-Operator.\n");
-			return false;
-		}
-		NESTED_ITER_PROFILE_END();
+			NESTED_ITER_PROFILE_BEGIN(NewtonApplyLinSolver);
+			if(!m_spLinearSolver->apply(u, *spD))
+			{
+				UG_LOG("ERROR in 'NestedIterationSolver::apply': Cannot apply Inverse Linear "
+						"Operator for Jacobi-Operator.\n");
+				return false;
+			}
+			NESTED_ITER_PROFILE_END();
 		}UG_CATCH_THROW("NestedIterationSolver::apply: Application of Linear Solver failed.");
 
 		// Adjust solution.
@@ -315,25 +318,34 @@ bool NestedIterationSolver<TDomain,TAlgebra>::apply(vector_type& u)
 			break;
 		}
 
-		// Refine domain and check error.
-		number err = this->refine_domain(usol);
+		// Estimate and mark domain.
+		this->estimate_and_mark_domain(usol, m_spRefinementMarking);
 
-		 if (m_spElemError.valid())
-		 {
-			 //	write defect for debug
-			 std::string name("NESTED_ITER_Error");
-			 name.append(ext);
-			 VTKOutput<TDomain::dim> outError;
-			 outError.print(name.c_str(), *m_spElemError);
+		//	OPTIONAL: write defect for debug
+		if (m_spElemError.valid())
+		{
+			std::string name("NESTED_ITER_Error");
+			name.append(ext);
+			VTKOutput<TDomain::dim> outError;
+			outError.print(name.c_str(), *m_spElemError);
 		}
 
+		// Check error.
+		const number err = m_spRefinementMarking->global_estimated_error();
+		double desiredTOL = (m_spAssociatedSpace.valid()) ? m_TOL*m_spAssociatedSpace->norm(usol) + m_absTOL : m_TOL;
+
+		UG_LOG("NI *** Desired tolerance: " << m_TOL << " * "<<  m_spAssociatedSpace->norm(usol) <<  " + "<< m_absTOL <<std::endl);
+
 		// Quit or continue?
-		if(err < m_TOL)
+		if(err < desiredTOL)
 		{
-			UG_LOG("SUCCESS: Error smaller than tolerance: " << err << " < "<< m_TOL << std::endl);
+			// Quit.
+			UG_LOG("SUCCESS: Error smaller than tolerance: " << err << " < "<< desiredTOL << std::endl);
 			break;
 		} else {
-			UG_LOG("FAILED: Error (still) greater than tolerance: " << err << " > "<< m_TOL << std::endl);
+			// Refine and continue.
+			UG_LOG("FAILED: Error (still) greater than tolerance: " << err << " > "<< desiredTOL << std::endl);
+			m_spRefiner->refine();
 		}
 	}