refactor(holistic_fusion): remove the holistic yaw factor

docs/docs_src/read_the_docs/9_changelog.md

@@ -5,6 +5,13 @@ Smaller fixes are not listed here; see the [commit history](https://github.com/l
 
 ## 2026
 
+### October 2026: Remove the holistic yaw factor (PR #56)
+
+* **`addUnaryYawAbsoluteMeasurement()` is again the classic yaw factor.** It constrains the yaw of the sensor frame in the world
+  frame and ignores the fixed frame of the measurement. The holistic variant through the fixed-frame alignment and
+  `addUnaryYawAbsoluteClassicMeasurement()` are removed. A yaw in a tilted fixed frame has no clear meaning. For an orientation
+  measurement in a fixed frame, use `addUnaryHeadingAbsoluteMeasurement()`.
+
 ### October 2026: Heading factor (PR #55)
 
 * **New `addUnaryHeadingAbsoluteMeasurement()`** (holistic interface). It takes the measured orientation of the sensor frame and

holistic_fusion/CMakeLists.txt

@@ -67,9 +67,6 @@ if(BUILD_TESTING)
     add_executable(yaw_factor_test tests/test_yaw_factor.cpp)
     target_link_libraries(yaw_factor_test PRIVATE holistic_fusion)
     add_test(NAME yaw_factor_test COMMAND yaw_factor_test)
-    add_executable(holistic_yaw_expression_test tests/test_holistic_yaw_expression.cpp)
-    target_link_libraries(holistic_yaw_expression_test PRIVATE holistic_fusion)
-    add_test(NAME holistic_yaw_expression_test COMMAND holistic_yaw_expression_test)
     add_executable(heading_expression_test tests/test_heading_expression.cpp)
     target_link_libraries(heading_expression_test PRIVATE holistic_fusion)
     add_test(NAME heading_expression_test COMMAND heading_expression_test)

holistic_fusion/include/holistic_fusion/interface/HolisticFusionClassic.h

@@ -28,9 +28,8 @@ class HolisticFusionClassic : virtual public HolisticFusion {
   //// Absolute Measurements
   void addUnaryRollAbsoluteMeasurement(const UnaryMeasurementXDAbsolute<double, 1>& roll_F_S) override;
   void addUnaryPitchAbsoluteMeasurement(const UnaryMeasurementXDAbsolute<double, 1>& pitch_F_S) override;
-  // Constrains the yaw of the sensor frame in the world frame, independent of the measurement's fixed frame. The
-  // holistic addUnaryYawAbsoluteMeasurement() goes through the fixed-frame alignment.
-  void addUnaryYawAbsoluteClassicMeasurement(const UnaryMeasurementXDAbsolute<double, 1>& yaw_W_S);
+  // Constrains the yaw of the sensor frame in the world frame, independent of the measurement's fixed frame
+  void addUnaryYawAbsoluteMeasurement(const UnaryMeasurementXDAbsolute<double, 1>& yaw_W_S) override;
 
   /// Binary Measurements
   void addBinaryPose3Measurement(const BinaryMeasurementXD<Eigen::Isometry3d, 6>& F_T_F_S) override;

holistic_fusion/include/holistic_fusion/interface/HolisticFusionHolistic.h

@@ -30,14 +30,11 @@ class HolisticFusionHolistic : virtual public HolisticFusion {
   void addUnaryPose3AbsoluteMeasurement(const UnaryMeasurementXDAbsolute<Eigen::Isometry3d, 6>& R_T_R_S,
                                         const bool addToOnlineSmootherFlag = true) override;
   void addUnaryPosition3AbsoluteMeasurement(UnaryMeasurementXDAbsolute<Eigen::Vector3d, 3>& R_t_R_S) override;
-  // In a fixed frame other than the world frame, the yaw goes through the alignment keyframe of that frame. Only a position or pose
-  // measurement of the same frame creates that keyframe, so add it first. The yaw measurement is skipped with a warning while the frame
-  // has no keyframe.
-  // TODO: Add a joint yaw and position measurement, which creates the keyframe itself.
-  void addUnaryYawAbsoluteMeasurement(const UnaryMeasurementXDAbsolute<double, 1>& R_yaw_R_S) override;
   // Constrains the rotation about the z-axis of the world between the estimated and the measured orientation R_M_S of the sensor frame
-  // in its fixed frame M. Unlike the yaw, it is defined for every attitude and leaves roll and pitch to the other measurements. Same
-  // fixed-frame keyframe requirement as the yaw.
+  // in its fixed frame M. Unlike the yaw, it is defined for every attitude and leaves roll and pitch to the other measurements.
+  // In a fixed frame other than the world frame, the heading goes through the alignment keyframe of that frame. Only a position or pose
+  // measurement of the same frame creates that keyframe, so add it first. The heading measurement is skipped with a warning while the
+  // frame has no keyframe.
   void addUnaryHeadingAbsoluteMeasurement(const UnaryMeasurementXDAbsolute<Eigen::Matrix3d, 1>& R_M_S);
   void addUnaryVelocity3AbsoluteMeasurement(UnaryMeasurementXDAbsolute<Eigen::Vector3d, 3>& R_v_R_S) override;
   //// Local Measurements: Fully Local

holistic_fusion/src/lib/HolisticFusionClassic.cpp

@@ -27,7 +27,7 @@ HolisticFusionClassic::HolisticFusionClassic() {
 }
 
 // Unary ----------------------------
-void HolisticFusionClassic::addUnaryYawAbsoluteClassicMeasurement(const UnaryMeasurementXDAbsolute<double, 1>& yaw_W_frame) {
+void HolisticFusionClassic::addUnaryYawAbsoluteMeasurement(const UnaryMeasurementXDAbsolute<double, 1>& yaw_W_frame) {
   // Only take actions if graph has been initialized
   if (!initedGraphFlag_) {
     return;

holistic_fusion/src/lib/HolisticFusionHolistic.cpp

@@ -17,7 +17,6 @@ Please see the LICENSE file that has been included as part of this package.
 #include "holistic_fusion/factors/gmsf_expression/GmsfUnaryExpressionAbsoluteHeading.h"
 #include "holistic_fusion/factors/gmsf_expression/GmsfUnaryExpressionAbsolutePose3.h"
 #include "holistic_fusion/factors/gmsf_expression/GmsfUnaryExpressionAbsolutePosition3.h"
-#include "holistic_fusion/factors/gmsf_expression/GmsfUnaryExpressionAbsoluteYaw.h"
 /// Local
 #include "holistic_fusion/factors/gmsf_expression/GmsfUnaryExpressionLocalVelocity3.h"
 
@@ -124,46 +123,6 @@ void HolisticFusionHolistic::addUnaryPosition3AbsoluteMeasurement(
   }
 }
 
-void HolisticFusionHolistic::addUnaryYawAbsoluteMeasurement(const UnaryMeasurementXDAbsolute<double, 1>& fixedFrame_yaw_fixedFrame_sensorFrame) {
-  // Valid measurement received
-  if (!validFirstMeasurementReceivedFlag_) {
-    validFirstMeasurementReceivedFlag_ = true;
-  }
-
-  // Only take actions if graph has been initialized
-  if (!initedGraphFlag_) {
-    return;
-  }
-
-  // Check for covariance violation
-  bool covarianceViolatedFlag = isCovarianceViolated_<1>(fixedFrame_yaw_fixedFrame_sensorFrame.unaryMeasurementNoiseDensity(),
-                                                         fixedFrame_yaw_fixedFrame_sensorFrame.covarianceViolationThreshold());
-  if (checkAndPrintCovarianceViolation_(fixedFrame_yaw_fixedFrame_sensorFrame.measurementName(), covarianceViolatedFlag)) {
-    return;
-  }
-
-  if (!hasAlignmentKeyframeForMeasurementWithoutPosition_(fixedFrame_yaw_fixedFrame_sensorFrame)) {
-    return;
-  }
-
-  // Create GMSF expression
-  auto gmsfUnaryExpressionYawPtr = std::make_shared<GmsfUnaryExpressionAbsoluteYaw>(
-      std::make_shared<UnaryMeasurementXDAbsolute<double, 1>>(fixedFrame_yaw_fixedFrame_sensorFrame), staticTransformsPtr_->getImuFrame(),
-      staticTransformsPtr_->rv_T_frame1_frame2(staticTransformsPtr_->getImuFrame(),
-                                               fixedFrame_yaw_fixedFrame_sensorFrame.sensorFrameName()),
-      graphConfigPtr_->createReferenceAlignmentKeyframeEveryNSeconds_);
-
-  // Add factor to graph
-  graphMgrPtr_->addUnaryHolisticFactor<GmsfUnaryExpressionAbsoluteYaw>(gmsfUnaryExpressionYawPtr);
-
-  // Optimize ---------------------------------------------------------------
-  {
-    // Mutex for optimizeGraph Flag
-    const std::lock_guard<std::mutex> optimizeGraphLock(optimizeGraphMutex_);
-    optimizeGraphFlag_ = true;
-  }
-}
-
 void HolisticFusionHolistic::addUnaryHeadingAbsoluteMeasurement(
     const UnaryMeasurementXDAbsolute<Eigen::Matrix3d, 1>& R_M_S) {
   // Valid measurement received