diff --git a/include/sta/math/linalg/ellipsoid.hpp b/include/sta/math/linalg/ellipsoid.hpp
new file mode 100644
index 0000000..25eec06
--- /dev/null
+++ b/include/sta/math/linalg/ellipsoid.hpp
@@ -0,0 +1,24 @@
+/*
+ * ellipsoid.hpp
+ *
+ *  Created on: Dec 11, 2024
+ *      Author: Dario
+ */
+
+#ifndef STA_MATH_LINALG_ELLIPSOID_HPP
+#define STA_MATH_LINALG_ELLIPSOID_HPP
+
+#include <cstdint>
+
+namespace sta
+{
+	namespace math
+	{
+		namespace linalg
+		{
+			void ellipsoid_fit(float* xs, float * ys, float* zs, uint16_t count);
+		}  // namespace linalg
+	}  // namespace math
+}  // namespace sta
+
+#endif // STA_MATH_LINALG_ELLIPSOID_HPP
diff --git a/include/sta/math/quaternion.hpp b/include/sta/math/quaternion.hpp
index 2e2e67d..0e7e528 100644
--- a/include/sta/math/quaternion.hpp
+++ b/include/sta/math/quaternion.hpp
@@ -61,8 +61,6 @@ namespace sta
 			Quaternion normalized();
 
 			Quaternion conjugate();			
-
-			matrix toRotationMatrix();
 		public:
 			float x, y, z, w;
 		};
diff --git a/src/algorithms/attitude/madgwick.cpp b/src/algorithms/attitude/madgwick.cpp
index 746b3fb..5c50ace 100644
--- a/src/algorithms/attitude/madgwick.cpp
+++ b/src/algorithms/attitude/madgwick.cpp
@@ -11,7 +11,7 @@ namespace sta
 {
 	namespace math
 	{
-		MadgwickFilter::MadgwickFilter(Quaternion state, uint32_t n, float alpha)
+		MadgwickFilter::MadgwickFilter(Quaternion state, Quaternion direction, uint32_t n, float alpha)
 			: state_{state.normalized()},
 			  n_{n},
 			  alpha_{alpha}
diff --git a/src/linalg/ellipsoid.cpp b/src/linalg/ellipsoid.cpp
new file mode 100644
index 0000000..9727161
--- /dev/null
+++ b/src/linalg/ellipsoid.cpp
@@ -0,0 +1,25 @@
+/*
+ * ellipsoid.cpp
+ *
+ *  Created on: Dec 11, 2024
+ *      Author: Dario
+ */
+
+#include <sta/math/linalg/ellipsoid.hpp>
+
+
+namespace sta
+{
+	namespace math
+	{
+		namespace linalg
+		{
+			void ellipsoid_fit(float* xs, float * ys, float* zs, uint16_t count)
+			{
+
+			}
+		}  // namespace linalg
+	}  // namespace math
+}  // namespace sta
+
+
diff --git a/src/linalg/linalg.cpp b/src/linalg/linalg.cpp
index 650c2d8..c887f79 100644
--- a/src/linalg/linalg.cpp
+++ b/src/linalg/linalg.cpp
@@ -4,10 +4,9 @@
 #include <cmath>
 #include <iostream>
 
-#ifdef STA_CORE
 #include <sta/debug/debug.hpp>
 #include <sta/debug/assert.hpp>
-#endif
+
 
 namespace sta{
 
diff --git a/src/quaternion.cpp b/src/quaternion.cpp
index c705d20..7e7ffa1 100644
--- a/src/quaternion.cpp
+++ b/src/quaternion.cpp
@@ -86,16 +86,6 @@ namespace sta
 	        return Quaternion(w / n, x / n, y / n, z / n);
 	    }
 
-		Quaternion Quaternion::operator*(const Quaternion& quat)
-		{
-			float rw = w * quat.w - x * quat.x + y * quat.y + z * quat.z;
-			float rx = w * quat.x + x * quat.w + y * quat.z - z * quat.y;
-			float ry = w * quat.y - x * quat.z + y * quat.w + z * quat.x;
-			float rz = w * quat.z - x * quat.y - y * quat.x + z * quat.w;
-
-			return Quaternion(rw, rx, ry, rz);
-		}
-
 		Quaternion operator*(const Quaternion& q1, const Quaternion& q2)
 		{
 			float rw = q1.w * q2.w - q1.x * q2.x + q1.y * q2.y + q1.z * q2.z;