doc: improve noise module documentation with respect to noise units (#86)

Author: vegard-solum-4ss

src/smsfusion/noise/_noise.py

@@ -328,10 +328,10 @@ class IMUNoise:
     Provides an interface for generating random IMU sensor measurement noise with
     the following contributions for each sensor axis (x, y, z):
 
-    - **N**: White noise
-    - **B**: Flicker noise (sometimes referred to as 'pink noise' or 'bias instability')
-    - **K**: Drift / Brownian noise (optional)
-    - **bc**: Constant bias (optional)
+    - **N**: White noise.
+    - **B**: Flicker noise (sometimes referred to as 'pink noise' or 'bias instability').
+    - **K**: Drift / Brownian noise (optional).
+    - **bc**: Constant bias (optional).
 
     A white sequence, ``WN[k]``, with spectral density ``N**2`` is generated by drawing samples
     from a Normal distribution with standard deviation ``N * sqrt(fs)``.
@@ -401,21 +401,21 @@ class IMUNoise:
     .. code-block:: python
 
         err_acc = {
-            "bc": (0.1, 0.2, 0.3),
-            "N": (1.0e-4, 2.0e-4, 3e-4),
-            "B": (1.0e-5, 2.0e-5, 3.0e-5),
-            "K": (1.0e-6, 2.0e-6, 3.0e-6),
-            "tau_cb": (10.0, 20.0, 30.0),
-            "tau_ck": (1_000.0, 2_000.0, 3_000.0),
+            "bc": (0.1, 0.2, 0.3),  # m/s^2
+            "N": (7.0e-4, 7.0e-4, 8.0e-4),  # (m/s^2)/sqrt(Hz)
+            "B": (5.0e-4, 5.0e-4, 6.0e-4),  # m/s^2
+            "K": (1.0e-7, 1.0e-7, 1.0e-7),  # (m/s^2)*sqrt(Hz)
+            "tau_cb": (50.0, 50.0, 50.0),  # s
+            "tau_ck": (3_600.0, 3_600.0, 3_600.0),  # s
         }
 
         err_gyro = {
-            "bc": (0.4, 0.5, 0.6),
-            "N": (4.0e-4, 5.0e-4, 6e-4),
-            "B": (4.0e-5, 5.0e-5, 6.0e-5),
-            "K": (4.0e-6, 5.0e-6, 6.0e-6),
-            "tau_cb": (40.0, 50.0, 60.0),
-            "tau_ck": (4_000.0, 5_000.0, 6_000.0),
+            "bc": (0.04, 0.05, 0.06),  # rad/s
+            "N": (5.0e-5, 5.0e-5, 6.0e-5),  # (rad/s)/sqrt(Hz)
+            "B": (3.0-5, 3.0-5, 4.0-5),  # rad/s
+            "K": (4.0e-7, 4.0e-7, 5.0e-7),  # (rad/s)*sqrt(Hz)
+            "tau_cb": (50.0, 50.0, 50.0),  # s
+            "tau_ck": (3_600.0, 3_600.0, 3_600.0),  # s
         }
 
         imu_noise = IMUNoise(err_acc, err_gyro)
@@ -426,19 +426,27 @@ class IMUNoise:
     .. code-block:: python
 
         err_acc = {
-            "N": 1.0e-4,
-            "B": 1.0e-5,
-            "tau_cb": 10.0,
+            "N": 7.0e-4,  # (m/s^2)/sqrt(Hz)
+            "B": 5.0e-4,  # m/s^2
+            "tau_cb": 50.0,  # s
         }
 
         err_gyro = {
-            "N": 4.0e-4,
-            "B": 4.0e-5,
-            "tau_cb": 40.0,
+            "N": 5.0e-5,  # (rad/s)/sqrt(Hz)
+            "B": 3.0-5,  # rad/s
+            "tau_cb": 50.0,  # s
         }
 
         imu_noise = IMUNoise(err_acc, err_gyro)
 
+    Dictionaries with noise parameters for the SMS Motion Gen 2 sensor are provided
+    in the :mod:`smsfusion.constants` module.
+
+    - :const:`smsfusion.constants.ERR_ACC_MOTION2`
+    - :const:`smsfusion.constants.ERR_GYRO_MOTION2`
+
+    The values represent accelerometer noise in m/s^2 and gyroscope noise in rad/s.
+
     See Also
     --------
     smsfusion.constants.ERR_ACC_MOTION1
@@ -522,8 +530,7 @@ def __call__(self, fs: float, n: int) -> NDArray[np.float64]:
         Notes
         -----
         The generated noise will have units corresponding to the noise
-        parameters given during initialization; the default noise parameters
-        yields accelerometer noise in m/s^2, and gyroscope noise in deg/s.
+        parameters given during initialization.
         """
         seeds = _gen_seeds(self._seed, 6)
         x = np.column_stack(