diff --git a/.cproject b/.cproject
index 946897361..4801c4641 100644
--- a/.cproject
+++ b/.cproject
@@ -1,17 +1,19 @@
 <?xml version="1.0" encoding="UTF-8" standalone="no"?>
-<?fileVersion 4.0.0?><cproject storage_type_id="org.eclipse.cdt.core.XmlProjectDescriptionStorage">
+<?fileVersion 4.0.0?>
+
+<cproject storage_type_id="org.eclipse.cdt.core.XmlProjectDescriptionStorage">
 	<storageModule moduleId="org.eclipse.cdt.core.settings">
 		<cconfiguration id="cdt.managedbuild.toolchain.gnu.macosx.base.1359703544">
 			<storageModule buildSystemId="org.eclipse.cdt.managedbuilder.core.configurationDataProvider" id="cdt.managedbuild.toolchain.gnu.macosx.base.1359703544" moduleId="org.eclipse.cdt.core.settings" name="MacOSX GCC">
 				<externalSettings/>
 				<extensions>
+					<extension id="org.eclipse.cdt.core.ELF" point="org.eclipse.cdt.core.BinaryParser"/>
+					<extension id="org.eclipse.cdt.core.MachO64" point="org.eclipse.cdt.core.BinaryParser"/>
 					<extension id="org.eclipse.cdt.core.GASErrorParser" point="org.eclipse.cdt.core.ErrorParser"/>
 					<extension id="org.eclipse.cdt.core.GLDErrorParser" point="org.eclipse.cdt.core.ErrorParser"/>
 					<extension id="org.eclipse.cdt.core.GCCErrorParser" point="org.eclipse.cdt.core.ErrorParser"/>
 					<extension id="org.eclipse.cdt.core.GmakeErrorParser" point="org.eclipse.cdt.core.ErrorParser"/>
 					<extension id="org.eclipse.cdt.core.CWDLocator" point="org.eclipse.cdt.core.ErrorParser"/>
-					<extension id="org.eclipse.cdt.core.ELF" point="org.eclipse.cdt.core.BinaryParser"/>
-					<extension id="org.eclipse.cdt.core.MachO64" point="org.eclipse.cdt.core.BinaryParser"/>
 				</extensions>
 			</storageModule>
 			<storageModule moduleId="cdtBuildSystem" version="4.0.0">
@@ -19,7 +21,7 @@
 					<folderInfo id="cdt.managedbuild.toolchain.gnu.macosx.base.1359703544.2031210194" name="/" resourcePath="">
 						<toolChain id="cdt.managedbuild.toolchain.gnu.macosx.base.677243255" name="cdt.managedbuild.toolchain.gnu.macosx.base" superClass="cdt.managedbuild.toolchain.gnu.macosx.base">
 							<targetPlatform archList="all" binaryParser="org.eclipse.cdt.core.ELF;org.eclipse.cdt.core.MachO64" id="cdt.managedbuild.target.gnu.platform.macosx.base.752782918" name="Debug Platform" osList="macosx" superClass="cdt.managedbuild.target.gnu.platform.macosx.base"/>
-							<builder arguments="" buildPath="${ProjDirPath}/build" command="make" id="cdt.managedbuild.target.gnu.builder.macosx.base.319933862" keepEnvironmentInBuildfile="false" managedBuildOn="false" name="Gnu Make Builder" parallelBuildOn="true" parallelizationNumber="5" superClass="cdt.managedbuild.target.gnu.builder.macosx.base"/>
+							<builder arguments="-j8" buildPath="${ProjDirPath}/build" command="make" id="cdt.managedbuild.target.gnu.builder.macosx.base.319933862" keepEnvironmentInBuildfile="false" managedBuildOn="false" name="Gnu Make Builder" parallelBuildOn="true" parallelizationNumber="optimal" superClass="cdt.managedbuild.target.gnu.builder.macosx.base"/>
 							<tool id="cdt.managedbuild.tool.macosx.c.linker.macosx.base.457360678" name="MacOS X C Linker" superClass="cdt.managedbuild.tool.macosx.c.linker.macosx.base"/>
 							<tool id="cdt.managedbuild.tool.macosx.cpp.linker.macosx.base.1011140787" name="MacOS X C++ Linker" superClass="cdt.managedbuild.tool.macosx.cpp.linker.macosx.base">
 								<option id="macosx.cpp.link.option.paths.451252615" name="Library search path (-L)" superClass="macosx.cpp.link.option.paths"/>
@@ -60,13 +62,13 @@
 			<storageModule buildSystemId="org.eclipse.cdt.managedbuilder.core.configurationDataProvider" id="cdt.managedbuild.toolchain.gnu.macosx.base.1359703544.1441575890" moduleId="org.eclipse.cdt.core.settings" name="Timing">
 				<externalSettings/>
 				<extensions>
+					<extension id="org.eclipse.cdt.core.ELF" point="org.eclipse.cdt.core.BinaryParser"/>
+					<extension id="org.eclipse.cdt.core.MachO64" point="org.eclipse.cdt.core.BinaryParser"/>
 					<extension id="org.eclipse.cdt.core.GASErrorParser" point="org.eclipse.cdt.core.ErrorParser"/>
 					<extension id="org.eclipse.cdt.core.GLDErrorParser" point="org.eclipse.cdt.core.ErrorParser"/>
 					<extension id="org.eclipse.cdt.core.GCCErrorParser" point="org.eclipse.cdt.core.ErrorParser"/>
 					<extension id="org.eclipse.cdt.core.GmakeErrorParser" point="org.eclipse.cdt.core.ErrorParser"/>
 					<extension id="org.eclipse.cdt.core.CWDLocator" point="org.eclipse.cdt.core.ErrorParser"/>
-					<extension id="org.eclipse.cdt.core.ELF" point="org.eclipse.cdt.core.BinaryParser"/>
-					<extension id="org.eclipse.cdt.core.MachO64" point="org.eclipse.cdt.core.BinaryParser"/>
 				</extensions>
 			</storageModule>
 			<storageModule moduleId="cdtBuildSystem" version="4.0.0">
@@ -116,13 +118,13 @@
 			<storageModule buildSystemId="org.eclipse.cdt.managedbuilder.core.configurationDataProvider" id="cdt.managedbuild.toolchain.gnu.macosx.base.1359703544.127261216" moduleId="org.eclipse.cdt.core.settings" name="fast">
 				<externalSettings/>
 				<extensions>
+					<extension id="org.eclipse.cdt.core.ELF" point="org.eclipse.cdt.core.BinaryParser"/>
+					<extension id="org.eclipse.cdt.core.MachO64" point="org.eclipse.cdt.core.BinaryParser"/>
 					<extension id="org.eclipse.cdt.core.GASErrorParser" point="org.eclipse.cdt.core.ErrorParser"/>
 					<extension id="org.eclipse.cdt.core.GLDErrorParser" point="org.eclipse.cdt.core.ErrorParser"/>
 					<extension id="org.eclipse.cdt.core.GCCErrorParser" point="org.eclipse.cdt.core.ErrorParser"/>
 					<extension id="org.eclipse.cdt.core.GmakeErrorParser" point="org.eclipse.cdt.core.ErrorParser"/>
 					<extension id="org.eclipse.cdt.core.CWDLocator" point="org.eclipse.cdt.core.ErrorParser"/>
-					<extension id="org.eclipse.cdt.core.ELF" point="org.eclipse.cdt.core.BinaryParser"/>
-					<extension id="org.eclipse.cdt.core.MachO64" point="org.eclipse.cdt.core.BinaryParser"/>
 				</extensions>
 			</storageModule>
 			<storageModule moduleId="cdtBuildSystem" version="4.0.0">
@@ -130,7 +132,7 @@
 					<folderInfo id="cdt.managedbuild.toolchain.gnu.macosx.base.1359703544.127261216." name="/" resourcePath="">
 						<toolChain id="cdt.managedbuild.toolchain.gnu.macosx.base.1052998998" name="cdt.managedbuild.toolchain.gnu.macosx.base" superClass="cdt.managedbuild.toolchain.gnu.macosx.base">
 							<targetPlatform archList="all" binaryParser="org.eclipse.cdt.core.ELF;org.eclipse.cdt.core.MachO64" id="cdt.managedbuild.target.gnu.platform.macosx.base.1735323246" name="Debug Platform" osList="macosx" superClass="cdt.managedbuild.target.gnu.platform.macosx.base"/>
-							<builder arguments="" buildPath="${workspace_loc:/gtsam/build-fast}" command="make" id="cdt.managedbuild.target.gnu.builder.macosx.base.1127775962" keepEnvironmentInBuildfile="false" managedBuildOn="false" name="Gnu Make Builder" parallelBuildOn="true" parallelizationNumber="5" superClass="cdt.managedbuild.target.gnu.builder.macosx.base"/>
+							<builder arguments="" buildPath="${workspace_loc:/gtsam/build-fast}" command="make" id="cdt.managedbuild.target.gnu.builder.macosx.base.1127775962" keepEnvironmentInBuildfile="false" managedBuildOn="false" name="Gnu Make Builder" parallelBuildOn="true" parallelizationNumber="optimal" superClass="cdt.managedbuild.target.gnu.builder.macosx.base"/>
 							<tool id="cdt.managedbuild.tool.macosx.c.linker.macosx.base.1922513433" name="MacOS X C Linker" superClass="cdt.managedbuild.tool.macosx.c.linker.macosx.base"/>
 							<tool id="cdt.managedbuild.tool.macosx.cpp.linker.macosx.base.1097733515" name="MacOS X C++ Linker" superClass="cdt.managedbuild.tool.macosx.cpp.linker.macosx.base">
 								<option id="macosx.cpp.link.option.paths.2077171343" name="Library search path (-L)" superClass="macosx.cpp.link.option.paths" valueType="libPaths">
@@ -582,6 +584,7 @@
 			</target>
 			<target name="tests/testBayesTree.run" path="inference" targetID="org.eclipse.cdt.build.MakeTargetBuilder">
 				<buildCommand>make</buildCommand>
+				<buildArguments/>
 				<buildTarget>tests/testBayesTree.run</buildTarget>
 				<stopOnError>true</stopOnError>
 				<useDefaultCommand>false</useDefaultCommand>
@@ -589,6 +592,7 @@
 			</target>
 			<target name="testBinaryBayesNet.run" path="inference" targetID="org.eclipse.cdt.build.MakeTargetBuilder">
 				<buildCommand>make</buildCommand>
+				<buildArguments/>
 				<buildTarget>testBinaryBayesNet.run</buildTarget>
 				<stopOnError>true</stopOnError>
 				<useDefaultCommand>false</useDefaultCommand>
@@ -636,6 +640,7 @@
 			</target>
 			<target name="testSymbolicBayesNet.run" path="inference" targetID="org.eclipse.cdt.build.MakeTargetBuilder">
 				<buildCommand>make</buildCommand>
+				<buildArguments/>
 				<buildTarget>testSymbolicBayesNet.run</buildTarget>
 				<stopOnError>true</stopOnError>
 				<useDefaultCommand>false</useDefaultCommand>
@@ -643,6 +648,7 @@
 			</target>
 			<target name="tests/testSymbolicFactor.run" path="inference" targetID="org.eclipse.cdt.build.MakeTargetBuilder">
 				<buildCommand>make</buildCommand>
+				<buildArguments/>
 				<buildTarget>tests/testSymbolicFactor.run</buildTarget>
 				<stopOnError>true</stopOnError>
 				<useDefaultCommand>false</useDefaultCommand>
@@ -650,6 +656,7 @@
 			</target>
 			<target name="testSymbolicFactorGraph.run" path="inference" targetID="org.eclipse.cdt.build.MakeTargetBuilder">
 				<buildCommand>make</buildCommand>
+				<buildArguments/>
 				<buildTarget>testSymbolicFactorGraph.run</buildTarget>
 				<stopOnError>true</stopOnError>
 				<useDefaultCommand>false</useDefaultCommand>
@@ -665,6 +672,7 @@
 			</target>
 			<target name="tests/testBayesTree" path="inference" targetID="org.eclipse.cdt.build.MakeTargetBuilder">
 				<buildCommand>make</buildCommand>
+				<buildArguments/>
 				<buildTarget>tests/testBayesTree</buildTarget>
 				<stopOnError>true</stopOnError>
 				<useDefaultCommand>false</useDefaultCommand>
@@ -902,6 +910,14 @@
 				<useDefaultCommand>true</useDefaultCommand>
 				<runAllBuilders>true</runAllBuilders>
 			</target>
+			<target name="testAttitudeFactor.run" path="build/gtsam/navigation/tests" targetID="org.eclipse.cdt.build.MakeTargetBuilder">
+				<buildCommand>make</buildCommand>
+				<buildArguments>-j8</buildArguments>
+				<buildTarget>testAttitudeFactor.run</buildTarget>
+				<stopOnError>true</stopOnError>
+				<useDefaultCommand>true</useDefaultCommand>
+				<runAllBuilders>true</runAllBuilders>
+			</target>
 			<target name="clean" path="build/wrap/gtsam" targetID="org.eclipse.cdt.build.MakeTargetBuilder">
 				<buildCommand>make</buildCommand>
 				<buildArguments>-j5</buildArguments>
@@ -1008,6 +1024,7 @@
 			</target>
 			<target name="testErrors.run" path="linear" targetID="org.eclipse.cdt.build.MakeTargetBuilder">
 				<buildCommand>make</buildCommand>
+				<buildArguments/>
 				<buildTarget>testErrors.run</buildTarget>
 				<stopOnError>true</stopOnError>
 				<useDefaultCommand>false</useDefaultCommand>
@@ -1237,6 +1254,46 @@
 				<useDefaultCommand>true</useDefaultCommand>
 				<runAllBuilders>true</runAllBuilders>
 			</target>
+			<target name="testBTree.run" path="build/gtsam_unstable/base/tests" targetID="org.eclipse.cdt.build.MakeTargetBuilder">
+				<buildCommand>make</buildCommand>
+				<buildArguments>-j5</buildArguments>
+				<buildTarget>testBTree.run</buildTarget>
+				<stopOnError>true</stopOnError>
+				<useDefaultCommand>true</useDefaultCommand>
+				<runAllBuilders>true</runAllBuilders>
+			</target>
+			<target name="testDSF.run" path="build/gtsam_unstable/base/tests" targetID="org.eclipse.cdt.build.MakeTargetBuilder">
+				<buildCommand>make</buildCommand>
+				<buildArguments>-j5</buildArguments>
+				<buildTarget>testDSF.run</buildTarget>
+				<stopOnError>true</stopOnError>
+				<useDefaultCommand>true</useDefaultCommand>
+				<runAllBuilders>true</runAllBuilders>
+			</target>
+			<target name="testDSFMap.run" path="build/gtsam_unstable/base/tests" targetID="org.eclipse.cdt.build.MakeTargetBuilder">
+				<buildCommand>make</buildCommand>
+				<buildArguments>-j5</buildArguments>
+				<buildTarget>testDSFMap.run</buildTarget>
+				<stopOnError>true</stopOnError>
+				<useDefaultCommand>true</useDefaultCommand>
+				<runAllBuilders>true</runAllBuilders>
+			</target>
+			<target name="testDSFVector.run" path="build/gtsam_unstable/base/tests" targetID="org.eclipse.cdt.build.MakeTargetBuilder">
+				<buildCommand>make</buildCommand>
+				<buildArguments>-j5</buildArguments>
+				<buildTarget>testDSFVector.run</buildTarget>
+				<stopOnError>true</stopOnError>
+				<useDefaultCommand>true</useDefaultCommand>
+				<runAllBuilders>true</runAllBuilders>
+			</target>
+			<target name="testFixedVector.run" path="build/gtsam_unstable/base/tests" targetID="org.eclipse.cdt.build.MakeTargetBuilder">
+				<buildCommand>make</buildCommand>
+				<buildArguments>-j5</buildArguments>
+				<buildTarget>testFixedVector.run</buildTarget>
+				<stopOnError>true</stopOnError>
+				<useDefaultCommand>true</useDefaultCommand>
+				<runAllBuilders>true</runAllBuilders>
+			</target>
 			<target name="all" path="slam" targetID="org.eclipse.cdt.build.MakeTargetBuilder">
 				<buildCommand>make</buildCommand>
 				<buildArguments>-j2</buildArguments>
@@ -1319,7 +1376,6 @@
 			</target>
 			<target name="testSimulated2DOriented.run" path="slam" targetID="org.eclipse.cdt.build.MakeTargetBuilder">
 				<buildCommand>make</buildCommand>
-				<buildArguments/>
 				<buildTarget>testSimulated2DOriented.run</buildTarget>
 				<stopOnError>true</stopOnError>
 				<useDefaultCommand>false</useDefaultCommand>
@@ -1359,7 +1415,6 @@
 			</target>
 			<target name="testSimulated2D.run" path="slam" targetID="org.eclipse.cdt.build.MakeTargetBuilder">
 				<buildCommand>make</buildCommand>
-				<buildArguments/>
 				<buildTarget>testSimulated2D.run</buildTarget>
 				<stopOnError>true</stopOnError>
 				<useDefaultCommand>false</useDefaultCommand>
@@ -1367,7 +1422,6 @@
 			</target>
 			<target name="testSimulated3D.run" path="slam" targetID="org.eclipse.cdt.build.MakeTargetBuilder">
 				<buildCommand>make</buildCommand>
-				<buildArguments/>
 				<buildTarget>testSimulated3D.run</buildTarget>
 				<stopOnError>true</stopOnError>
 				<useDefaultCommand>false</useDefaultCommand>
@@ -1381,46 +1435,6 @@
 				<useDefaultCommand>true</useDefaultCommand>
 				<runAllBuilders>true</runAllBuilders>
 			</target>
-			<target name="testBTree.run" path="build/gtsam_unstable/base/tests" targetID="org.eclipse.cdt.build.MakeTargetBuilder">
-				<buildCommand>make</buildCommand>
-				<buildArguments>-j5</buildArguments>
-				<buildTarget>testBTree.run</buildTarget>
-				<stopOnError>true</stopOnError>
-				<useDefaultCommand>true</useDefaultCommand>
-				<runAllBuilders>true</runAllBuilders>
-			</target>
-			<target name="testDSF.run" path="build/gtsam_unstable/base/tests" targetID="org.eclipse.cdt.build.MakeTargetBuilder">
-				<buildCommand>make</buildCommand>
-				<buildArguments>-j5</buildArguments>
-				<buildTarget>testDSF.run</buildTarget>
-				<stopOnError>true</stopOnError>
-				<useDefaultCommand>true</useDefaultCommand>
-				<runAllBuilders>true</runAllBuilders>
-			</target>
-			<target name="testDSFMap.run" path="build/gtsam_unstable/base/tests" targetID="org.eclipse.cdt.build.MakeTargetBuilder">
-				<buildCommand>make</buildCommand>
-				<buildArguments>-j5</buildArguments>
-				<buildTarget>testDSFMap.run</buildTarget>
-				<stopOnError>true</stopOnError>
-				<useDefaultCommand>true</useDefaultCommand>
-				<runAllBuilders>true</runAllBuilders>
-			</target>
-			<target name="testDSFVector.run" path="build/gtsam_unstable/base/tests" targetID="org.eclipse.cdt.build.MakeTargetBuilder">
-				<buildCommand>make</buildCommand>
-				<buildArguments>-j5</buildArguments>
-				<buildTarget>testDSFVector.run</buildTarget>
-				<stopOnError>true</stopOnError>
-				<useDefaultCommand>true</useDefaultCommand>
-				<runAllBuilders>true</runAllBuilders>
-			</target>
-			<target name="testFixedVector.run" path="build/gtsam_unstable/base/tests" targetID="org.eclipse.cdt.build.MakeTargetBuilder">
-				<buildCommand>make</buildCommand>
-				<buildArguments>-j5</buildArguments>
-				<buildTarget>testFixedVector.run</buildTarget>
-				<stopOnError>true</stopOnError>
-				<useDefaultCommand>true</useDefaultCommand>
-				<runAllBuilders>true</runAllBuilders>
-			</target>
 			<target name="testEliminationTree.run" path="build/gtsam/inference/tests" targetID="org.eclipse.cdt.build.MakeTargetBuilder">
 				<buildCommand>make</buildCommand>
 				<buildArguments>-j5</buildArguments>
@@ -1678,6 +1692,7 @@
 			</target>
 			<target name="Generate DEB Package" path="" targetID="org.eclipse.cdt.build.MakeTargetBuilder">
 				<buildCommand>cpack</buildCommand>
+				<buildArguments/>
 				<buildTarget>-G DEB</buildTarget>
 				<stopOnError>true</stopOnError>
 				<useDefaultCommand>false</useDefaultCommand>
@@ -1685,6 +1700,7 @@
 			</target>
 			<target name="Generate RPM Package" path="" targetID="org.eclipse.cdt.build.MakeTargetBuilder">
 				<buildCommand>cpack</buildCommand>
+				<buildArguments/>
 				<buildTarget>-G RPM</buildTarget>
 				<stopOnError>true</stopOnError>
 				<useDefaultCommand>false</useDefaultCommand>
@@ -1692,6 +1708,7 @@
 			</target>
 			<target name="Generate TGZ Package" path="" targetID="org.eclipse.cdt.build.MakeTargetBuilder">
 				<buildCommand>cpack</buildCommand>
+				<buildArguments/>
 				<buildTarget>-G TGZ</buildTarget>
 				<stopOnError>true</stopOnError>
 				<useDefaultCommand>false</useDefaultCommand>
@@ -1699,6 +1716,7 @@
 			</target>
 			<target name="Generate TGZ Source Package" path="" targetID="org.eclipse.cdt.build.MakeTargetBuilder">
 				<buildCommand>cpack</buildCommand>
+				<buildArguments/>
 				<buildTarget>--config CPackSourceConfig.cmake</buildTarget>
 				<stopOnError>true</stopOnError>
 				<useDefaultCommand>false</useDefaultCommand>
@@ -2425,6 +2443,7 @@
 			</target>
 			<target name="testGraph.run" path="build/tests" targetID="org.eclipse.cdt.build.MakeTargetBuilder">
 				<buildCommand>make</buildCommand>
+				<buildArguments/>
 				<buildTarget>testGraph.run</buildTarget>
 				<stopOnError>true</stopOnError>
 				<useDefaultCommand>false</useDefaultCommand>
@@ -2432,6 +2451,7 @@
 			</target>
 			<target name="testJunctionTree.run" path="build/tests" targetID="org.eclipse.cdt.build.MakeTargetBuilder">
 				<buildCommand>make</buildCommand>
+				<buildArguments/>
 				<buildTarget>testJunctionTree.run</buildTarget>
 				<stopOnError>true</stopOnError>
 				<useDefaultCommand>false</useDefaultCommand>
@@ -2439,6 +2459,7 @@
 			</target>
 			<target name="testSymbolicBayesNetB.run" path="build/tests" targetID="org.eclipse.cdt.build.MakeTargetBuilder">
 				<buildCommand>make</buildCommand>
+				<buildArguments/>
 				<buildTarget>testSymbolicBayesNetB.run</buildTarget>
 				<stopOnError>true</stopOnError>
 				<useDefaultCommand>false</useDefaultCommand>
@@ -2902,7 +2923,6 @@
 			</target>
 			<target name="tests/testGaussianISAM2" path="build/slam" targetID="org.eclipse.cdt.build.MakeTargetBuilder">
 				<buildCommand>make</buildCommand>
-				<buildArguments/>
 				<buildTarget>tests/testGaussianISAM2</buildTarget>
 				<stopOnError>true</stopOnError>
 				<useDefaultCommand>false</useDefaultCommand>
diff --git a/gtsam.h b/gtsam.h
index 655d587ae..9427f4c32 100644
--- a/gtsam.h
+++ b/gtsam.h
@@ -2357,6 +2357,9 @@ class AHRSFactorPreintegratedMeasurements {
   void print(string s) const;
   bool equals(const gtsam::AHRSFactorPreintegratedMeasurements& expected, double tol);
 
+  // get Data
+  Matrix MeasurementCovariance();
+
   // Standard Interface
   void integrateMeasurement(Vector measuredOmega, double deltaT);
   void integrateMeasurement(Vector measuredOmega, double deltaT, const gtsam::Pose3& body_P_sensor);
@@ -2420,6 +2423,22 @@ virtual class CombinedImuFactor : gtsam::NonlinearFactor {
       Vector gravity, Vector omegaCoriolis) const;
 };
 
+#include <gtsam/navigation/AttitudeFactor.h>
+//virtual class AttitudeFactor : gtsam::NonlinearFactor {
+//  AttitudeFactor(const Unit3& nZ, const Unit3& bRef);
+//  AttitudeFactor();
+//};
+virtual class Rot3AttitudeFactor : gtsam::NonlinearFactor{
+  Rot3AttitudeFactor(size_t key, const gtsam::Unit3& nZ, const gtsam::noiseModel::Diagonal* model,
+      const gtsam::Unit3& bRef);
+  Rot3AttitudeFactor(size_t key, const gtsam::Unit3& nZ, const gtsam::noiseModel::Diagonal* model);
+  Rot3AttitudeFactor();
+  void print(string s) const;
+  bool equals(const gtsam::NonlinearFactor& expected, double tol) const;
+  gtsam::Unit3 nZ() const;
+  gtsam::Unit3 bRef() const;
+};
+
 //*************************************************************************
 // Utilities
 //*************************************************************************
diff --git a/gtsam/navigation/AHRSFactor.h b/gtsam/navigation/AHRSFactor.h
index 17531c8a4..ada073943 100644
--- a/gtsam/navigation/AHRSFactor.h
+++ b/gtsam/navigation/AHRSFactor.h
@@ -64,6 +64,9 @@ public:
               && equal_with_abs_tol(delRdelBiasOmega, expected.delRdelBiasOmega,
                   tol);
     }
+    Matrix MeasurementCovariance(){
+      return measurementCovariance;
+    }
 
     void resetIntegration() {
       deltaRij = Rot3();
diff --git a/gtsam/navigation/AttitudeFactor.h b/gtsam/navigation/AttitudeFactor.h
index 64603bd99..9338f3dba 100644
--- a/gtsam/navigation/AttitudeFactor.h
+++ b/gtsam/navigation/AttitudeFactor.h
@@ -110,6 +110,12 @@ public:
       boost::optional<Matrix&> H = boost::none) const {
     return attitudeError(nRb, H);
   }
+  Unit3 nZ() const {
+    return nZ_;
+  }
+  Unit3 bRef() const {
+    return bRef_;
+  }
 
 private: