diff --git a/Modules/ImageStatistics/mitkPointSetStatisticsCalculator.cpp b/Modules/ImageStatistics/mitkPointSetStatisticsCalculator.cpp
index 9756a6977a..a0c90d7dc9 100644
--- a/Modules/ImageStatistics/mitkPointSetStatisticsCalculator.cpp
+++ b/Modules/ImageStatistics/mitkPointSetStatisticsCalculator.cpp
@@ -1,247 +1,259 @@
 /*=========================================================================
 
 Program:   Medical Imaging & Interaction Toolkit
 Language:  C++
 Date:      $Date: 2009-05-12 19:56:03 +0200 (Di, 12 Mai 2009) $
 Version:   $Revision: 17179 $
 
 Copyright (c) German Cancer Research Center, Division of Medical and
 Biological Informatics. All rights reserved.
 See MITKCopyright.txt or http://www.mitk.org/copyright.html for details.
 
 This software is distributed WITHOUT ANY WARRANTY; without even
 the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
 PURPOSE.  See the above copyright notices for more information.
 
 =========================================================================*/
 
 
 #include "mitkPointSetStatisticsCalculator.h"
 
 mitk::PointSetStatisticsCalculator::PointSetStatisticsCalculator()
 {
   m_PointSet = mitk::PointSet::New();
 }
 
 mitk::PointSetStatisticsCalculator::PointSetStatisticsCalculator(mitk::PointSet::Pointer pSet)
 {
   m_PointSet = pSet;
 }
 
 mitk::PointSetStatisticsCalculator::~PointSetStatisticsCalculator()
 {
 }
 
 void mitk::PointSetStatisticsCalculator::SetPointSet(mitk::PointSet::Pointer pSet)
 {
   if (pSet.IsNull()) return;
   m_PointSet = pSet;
 }
 
 std::vector<mitk::Point3D> mitk::PointSetStatisticsCalculator::PointSetToVector(mitk::PointSet::Pointer pSet)
 {
   std::vector<mitk::Point3D> returnValue = std::vector<mitk::Point3D>();
   for (int i=0; i<pSet->GetSize(); i++) returnValue.push_back(pSet->GetPoint(i));
   return returnValue;
 }
 
 double mitk::PointSetStatisticsCalculator::GetMax(std::vector<double> list)
 {
+if (list.empty()) return 0;
 std::sort(list.begin(), list.end());
 return list.at(list.size()-1);
 }
 
 double mitk::PointSetStatisticsCalculator::GetMin(std::vector<double> list)
 {
+if (list.empty()) return 0;
 std::sort(list.begin(), list.end());
 return list.at(0);
 }
 
 double mitk::PointSetStatisticsCalculator::GetStabw(std::vector<double> list)
 {
+if (list.empty()) return 0;
 double returnValue = 0;
 double mean = GetMean(list);
 for(int i=0; i<list.size(); i++)
   {
   returnValue += pow((list.at(i)-mean),2);
   }
 
 returnValue /= list.size();
 returnValue = sqrt(returnValue);
 return returnValue;
 }
 
 double mitk::PointSetStatisticsCalculator::GetSampleStabw(std::vector<double> list)
 {
+if (list.empty()) return 0;
 double returnValue = 0;
 double mean = GetMean(list);
 for(int i=0; i<list.size(); i++)
   {
   returnValue += pow((list.at(i)-mean),2);
   }
 
 returnValue /= (list.size()-1);
 returnValue = sqrt(returnValue);
 return returnValue;
 }
 
 double mitk::PointSetStatisticsCalculator::GetMean(std::vector<double> list)
 {
+if (list.empty()) return 0;
 double mean = 0;
 for(int i=0; i<list.size(); i++)
   {
   mean += list.at(i);
   }
 mean /= list.size();
 return mean;
 }
 
 double mitk::PointSetStatisticsCalculator::GetMedian(std::vector<double> list)
 {
+if (list.empty()) return 0;
 std::sort(list.begin(), list.end());
 if (list.size() % 2 == 0.) //even
   {
   double element1 = list.at(list.size()/2);
   double element2 = list.at(list.size()/2);
   return ((element1+element2)/2.0);
   }
 else //odd
   {
   return list.at((list.size())/2);
   }
 }
 
 mitk::Point3D mitk::PointSetStatisticsCalculator::GetMean(std::vector<mitk::Point3D> list)
 {
+if (list.empty()) return 0;
+
 //calculate mean
 mitk::Point3D mean;
 mean.Fill(0);
 
 for (int i=0; i<list.size(); i++)
   {
   mean[0] += list.at(i)[0];
   mean[1] += list.at(i)[1];
   mean[2] += list.at(i)[2];
   }
 
 mean[0] /= list.size();
 mean[1] /= list.size();
 mean[2] /= list.size();
 
 return mean;
 }
 
 double mitk::PointSetStatisticsCalculator::GetPositionErrorMean()
 {
 double returnValue = 0.0;
 
 std::vector<mitk::Point3D> pSet = PointSetToVector(m_PointSet);
 
+if (pSet.empty()) return 0;
+
 mitk::Point3D mean = GetMean(pSet);
 
 for(int i=0; i<pSet.size(); i++)
   {
   returnValue += mean.EuclideanDistanceTo(pSet.at(i));
   }
 returnValue /= pSet.size();
 
 return returnValue;
 }
 
 double mitk::PointSetStatisticsCalculator::GetPositionErrorStandardDeviation()
 {
 return GetStabw(GetErrorList(PointSetToVector(m_PointSet)));
 }
 
 double mitk::PointSetStatisticsCalculator::GetPositionErrorSampleStandardDeviation()
 {
 return GetSampleStabw(GetErrorList(PointSetToVector(m_PointSet)));
 }
 
 
 double mitk::PointSetStatisticsCalculator::GetPositionErrorRMS()
 {
 double returnValue = 0.0;
 
 std::vector<mitk::Point3D> pSet = PointSetToVector(m_PointSet);
 
+if(pSet.empty()) return 0;
+
 mitk::Point3D mean = GetMean(pSet);
 
 for(int i=0; i<pSet.size(); i++)
   {
   returnValue += pow(mean.EuclideanDistanceTo(pSet.at(i)),2);
   }
 returnValue /= pSet.size();
 returnValue = sqrt(returnValue);
 
 return returnValue;
 }
 
 double mitk::PointSetStatisticsCalculator::GetPositionErrorMedian()
 {
 return GetMedian(GetErrorList(PointSetToVector(m_PointSet)));
 }
 
 double mitk::PointSetStatisticsCalculator::GetPositionErrorMax()
 {
 return GetMax(GetErrorList(PointSetToVector(m_PointSet)));
 }
   
 double mitk::PointSetStatisticsCalculator::GetPositionErrorMin()
 {
 return GetMin(GetErrorList(PointSetToVector(m_PointSet)));
 }
 
 std::vector<double> mitk::PointSetStatisticsCalculator::GetErrorList(std::vector<mitk::Point3D> list)
 {
 std::vector<double> errorList = std::vector<double>();
 mitk::Point3D mean = GetMean(list);
 for(int i=0; i<list.size(); i++)
   {
   errorList.push_back(mean.EuclideanDistanceTo(list.at(i)));
   }
 return errorList;
 }
 
 mitk::Vector3D mitk::PointSetStatisticsCalculator::GetPositionStandardDeviation()
 {
 mitk::Vector3D returnValue;
 std::vector<mitk::Point3D> pSet = PointSetToVector(m_PointSet);
 std::vector<double> listX = std::vector<double>();
 std::vector<double> listY = std::vector<double>();
 std::vector<double> listZ = std::vector<double>();
 for (int i=0; i<pSet.size(); i++)
   {
   listX.push_back(pSet.at(i)[0]);
   listY.push_back(pSet.at(i)[1]);
   listZ.push_back(pSet.at(i)[2]);
   }
 returnValue[0] = GetStabw(listX);
 returnValue[1] = GetStabw(listY);
 returnValue[2] = GetStabw(listZ);
 return returnValue;
 }
 
 mitk::Vector3D mitk::PointSetStatisticsCalculator::GetPositionSampleStandardDeviation()
 {
 mitk::Vector3D returnValue;
 std::vector<mitk::Point3D> pSet = PointSetToVector(m_PointSet);
 std::vector<double> listX = std::vector<double>();
 std::vector<double> listY = std::vector<double>();
 std::vector<double> listZ = std::vector<double>();
 for (int i=0; i<pSet.size(); i++)
   {
   listX.push_back(pSet.at(i)[0]);
   listY.push_back(pSet.at(i)[1]);
   listZ.push_back(pSet.at(i)[2]);
   }
 returnValue[0] = GetSampleStabw(listX);
 returnValue[1] = GetSampleStabw(listY);
 returnValue[2] = GetSampleStabw(listZ);
 return returnValue;
 }
 
 mitk::Point3D mitk::PointSetStatisticsCalculator::GetPositionMean()
 {
 return GetMean(PointSetToVector(m_PointSet));
 }
diff --git a/Modules/ImageStatistics/mitkPointSetStatisticsCalculator.h b/Modules/ImageStatistics/mitkPointSetStatisticsCalculator.h
index 8fb8d2a61e..69fd6433ec 100644
--- a/Modules/ImageStatistics/mitkPointSetStatisticsCalculator.h
+++ b/Modules/ImageStatistics/mitkPointSetStatisticsCalculator.h
@@ -1,118 +1,118 @@
 /*=========================================================================
 
 Program:   Medical Imaging & Interaction Toolkit
 Language:  C++
 Date:      $Date: 2009-05-12 19:56:03 +0200 (Di, 12 Mai 2009) $
 Version:   $Revision: 17179 $
 
 Copyright (c) German Cancer Research Center, Division of Medical and
 Biological Informatics. All rights reserved.
 See MITKCopyright.txt or http://www.mitk.org/copyright.html for details.
 
 This software is distributed WITHOUT ANY WARRANTY; without even
 the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
 PURPOSE.  See the above copyright notices for more information.
 
 =========================================================================*/
 
 
 #ifndef _MITK_PointSetSTATISTICSCALCULATOR_H
 #define _MITK_PointSetSTATISTICSCALCULATOR_H
 
 #include <itkObject.h>
 #include "ImageStatisticsExports.h"
 #include <mitkPointSet.h>
 
 namespace mitk
 {
 
 /**
  * \brief Class for calculating statistics (like standard derivation, RMS, mean, etc.) for a PointSet.
  */
 class ImageStatistics_EXPORT PointSetStatisticsCalculator : public itk::Object
 {
 public: 
   
   mitkClassMacro( PointSetStatisticsCalculator, itk::Object );
   itkNewMacro( PointSetStatisticsCalculator );
 
   mitkNewMacro1Param(PointSetStatisticsCalculator,mitk::PointSet::Pointer)
 
   /** @brief Sets the point set which will be analysed. */
   void SetPointSet(mitk::PointSet::Pointer pSet);
 
-  /** @return Returns the mean position of the analysed point set.*/
+  /** @return Returns the mean position of the analysed point set (only valid navigation data). Returns [0;0;0] if there is no valid navigation data.*/
   mitk::Point3D GetPositionMean();
   
-  /** @return Returns the standard derivation of each component (x, y and z) of the analysed point set.*/
+  /** @return Returns the standard derivation of each component (x, y and z) of the analysed point set (only valid navigation data). Returns [0;0;0] if there is no valid navigation data.*/
   mitk::Vector3D GetPositionStandardDeviation();
   
-  /** @return Returns the sample standard derivation of each component (x, y and z) of the analysed point set.*/
+  /** @return Returns the sample standard derivation of each component (x, y and z) of the analysed point set (only valid navigation data). Returns [0;0;0] if there is no valid navigation data.*/
   mitk::Vector3D GetPositionSampleStandardDeviation();
 
-  /** @return Returns the mean distance to the mean postion (=mean error) of the analysed point set. */
+  /** @return Returns the mean distance to the mean postion (=mean error) of the analysed point set (only valid navigation data). Returns 0 if there is no valid navigation data. */
   double GetPositionErrorMean();
   
-  /** @return Returns the standard derivation of the errors of all positions of the analysed point set. */
+  /** @return Returns the standard derivation of the errors of all positions of the analysed point set (only valid navigation data). Returns 0 if there is no valid navigation data. */
   double GetPositionErrorStandardDeviation();
  
-  /** @return Returns the sample standard derivation of the errors of all positions of the analysed point set. */
+  /** @return Returns the sample standard derivation of the errors of all positions of the analysed point set (only valid navigation data). Returns 0 if there is no valid navigation data. */
   double GetPositionErrorSampleStandardDeviation();
 
-  /** @return Returns the RMS of the errors of all positions of the analysed point set. */
+  /** @return Returns the RMS of the errors of all positions of the analysed point set (only valid navigation data). Returns 0 if there is no valid navigation data. */
   double GetPositionErrorRMS();
  
-  /** @return Returns the median of the errors of all positions of the analysed point set. */
+  /** @return Returns the median of the errors of all positions of the analysed point set (only valid navigation data). Returns 0 if there is no valid navigation data. */
   double GetPositionErrorMedian();
  
-  /** @return Returns the maximum of the errors of all positions of the analysed point set. */
+  /** @return Returns the maximum of the errors of all positions of the analysed point set (only valid navigation data). Returns 0 if there is no valid navigation data. */
   double GetPositionErrorMax();
  
-  /** @return Returns the minimum of the errors of all positions of the analysed point set. */
+  /** @return Returns the minimum of the errors of all positions of the analysed point set (only valid navigation data). Returns 0 if there is no valid navigation data. */
   double GetPositionErrorMin();
 
   //#####################################################################################################
 
   //this both methods are used by another class an so they are public... perhaps we want to move them
   //out of this class because they have nothing to do with point sets.
 
   /** @return returns the standard derivation of the given list (NOT of the point set).*/
   double GetStabw(std::vector<double> list);
 
   /** @return returns the sample standard derivation of the given list (NOT of the point set).*/
   double GetSampleStabw(std::vector<double> list);
 
   //#####################################################################################################
 
  
 protected:
   
   PointSetStatisticsCalculator();
   PointSetStatisticsCalculator(mitk::PointSet::Pointer);
   virtual ~PointSetStatisticsCalculator();
 
   // TODO: Remove the std::vector<mitk::Point3D> data structure and use mitk::PointSet everywhere
   
   /** @return Returns a list with the distances to the mean of the list */
   std::vector<double> GetErrorList(std::vector<mitk::Point3D> list);
 
   mitk::Point3D GetMean(std::vector<mitk::Point3D> list);
 
   /** @brief Converts a point set to a vector of Point3D. */
   std::vector<mitk::Point3D> PointSetToVector(mitk::PointSet::Pointer pSet);
 
   mitk::PointSet::Pointer m_PointSet;
 
   double GetMean(std::vector<double> list);
 
   double GetMedian(std::vector<double> list);
 
   double GetMax(std::vector<double> list);
 
   double GetMin(std::vector<double> list);
   
 };
 
 }
 
 #endif // #define _MITK_PointSetSTATISTICSCALCULATOR_H
\ No newline at end of file