diff --git a/src/sensor_base.cpp b/src/sensor_base.cpp
index 1ea1ed3d57c04c74b10ef6e2482fa72c545afcff..ae29d749135771d38ca051151eabde4ab14eee3b 100644
--- a/src/sensor_base.cpp
+++ b/src/sensor_base.cpp
@@ -145,12 +145,13 @@ void SensorBase::unfixIntrinsics()
     updateCalibSize();
 }
 
-void SensorBase::addParameterPrior(const StateBlockPtr& _sb, const Eigen::VectorXs& _x, const Eigen::MatrixXs& _cov, unsigned int _start_idx = 0, int _size = -1)
+void SensorBase::addParameterPrior(const StateBlockPtr& _sb, const Eigen::VectorXs& _x, const Eigen::MatrixXs& _cov, unsigned int _start_idx, int _size)
 {
     assert(std::find(state_block_vec_.begin(),state_block_vec_.end(),_sb) != state_block_vec_.end() && "adding prior to unknown state block");
     assert(_x.size() == _cov.rows() && _x.size() == _cov.cols() && "covariance and prior dimension should be the same");
     assert((_size == -1 && _start_idx == 0) || (_size+_start_idx <= _sb->getSize()));
     assert(_size == -1 || _size == _x.size());
+    assert(params_prior_map_.find(_sb) == params_prior_map_.end() && "this parameter has already a prior");
 
     // create feature
     auto ftr_prior = std::make_shared<FeatureBase>(_x,_cov);
@@ -163,6 +164,9 @@ void SensorBase::addParameterPrior(const StateBlockPtr& _sb, const Eigen::Vector
         ftr_prior->addConstraint(std::make_shared<ConstraintQuaternionAbsolute>(_sb));
     else
         ftr_prior->addConstraint(std::make_shared<ConstraintBlockAbsolute>(_sb, _start_idx, _size));
+
+    // store feature in params_prior_map_
+    params_prior_map_[_sb] = ftr_prior;
 }
 
 void SensorBase::registerNewStateBlocks()
diff --git a/src/sensor_base.h b/src/sensor_base.h
index 0fb7d8eb879f1183918fa446c22f12f6539fc33e..b97c65976c5baebc7c1e5614e504e79c26c16343 100644
--- a/src/sensor_base.h
+++ b/src/sensor_base.h
@@ -51,7 +51,7 @@ class SensorBase : public NodeBase, public std::enable_shared_from_this<SensorBa
         Eigen::VectorXs noise_std_; // std of sensor noise
         Eigen::MatrixXs noise_cov_; // cov matrix of noise
 
-        FeatureBaseList params_prior_list_; // Priors (value and covariance) of extrinsic & intrinsic parameters
+        std::map<StateBlockPtr,FeatureBasePtr> params_prior_map_; // Priors (value and covariance) of extrinsic & intrinsic state blocks (multimap
 
     public:
         /** \brief Constructor with noise size
@@ -93,7 +93,6 @@ class SensorBase : public NodeBase, public std::enable_shared_from_this<SensorBa
                    const bool _intr_dyn = false);
 
         virtual ~SensorBase();
-        void remove();
 
         unsigned int id();
 
@@ -136,7 +135,21 @@ class SensorBase : public NodeBase, public std::enable_shared_from_this<SensorBa
         void unfixExtrinsics();
         void fixIntrinsics();
         void unfixIntrinsics();
-        void addParameterPrior(const StateBlockPtr& _sb, const Eigen::VectorXs& _x, const Eigen::MatrixXs& _cov, unsigned int _start_idx = 0, int _size = -1);
+        /** \brief Add an absolute constraint to a parameter
+         *
+         * Add an absolute constraint to a parameter
+         * \param _sb state block of the parameter to be constrained
+         * \param _x prior value
+         * \param _cov covariance
+         * \param _start_idx state segment starting index (not used in quaternions)
+         * \param _size state segment size (-1: whole state) (not used in quaternions)
+         *
+         **/
+        void addParameterPrior(const StateBlockPtr& _sb,
+                               const Eigen::VectorXs& _x,
+                               const Eigen::MatrixXs& _cov,
+                               unsigned int _start_idx = 0,
+                               int _size = -1);
 
         SizeEigen getCalibSize() const;
         Eigen::VectorXs getCalibration() const;
@@ -201,6 +214,7 @@ inline StateBlockPtr SensorBase::getStateBlockPtrStatic(unsigned int _i) const
 
 inline void SensorBase::setStateBlockPtrStatic(unsigned int _i, const StateBlockPtr _sb_ptr)
 {
+    assert((params_prior_map_.find(state_block_vec_[_i]) == params_prior_map_.end() || _sb_ptr == nullptr) && "overwriting a state block that has an absolute constraint");
     state_block_vec_[_i] = _sb_ptr;
 }