Minor fixes and doc builds

Author: kanhereashwin

gnss_lib_py/algorithms/snapshot.py

@@ -218,11 +218,11 @@ def wls(rx_est_m, pos_sv_m, corr_pr_m, weights = None,
     frame of reference in which their position is calculated.
 
     This update happens after every Gauss-Newton update step and is
-    adapted from [1]__.
+    adapted from [1]_.
 
     References
     ----------
-        .. [1] https://github.com/google/gps-measurement-tools/blob/master/opensource/FlightTimeCorrection.m
+    .. [1] https://github.com/google/gps-measurement-tools/blob/master/opensource/FlightTimeCorrection.m
 
     """
 

gnss_lib_py/utils/sim_gnss.py

@@ -316,10 +316,10 @@ def _find_delxyz_range(sv_posvel, pos, satellites):
     pos = np.reshape(pos, [1, 3])
     if np.size(pos)!=3:
         raise ValueError('Position is not in XYZ')
-    if isinstance(sv_posvel, NavData):
-        _, sv_pos, _ = _extract_pos_vel_arr(sv_posvel)
-    else:
+    if isinstance(sv_posvel, np.ndarray):
         sv_pos = sv_posvel[:, :3]
+    else:
+        _, sv_pos, _ = _extract_pos_vel_arr(sv_posvel)
     del_pos = sv_pos - np.tile(np.reshape(pos, [-1, 3]), (satellites, 1))
     true_range = np.linalg.norm(del_pos, axis=1)
     return del_pos, true_range

notebooks/tutorials/algorithms.ipynb

@@ -35,7 +35,13 @@
    "id": "3bc6b5dd",
    "metadata": {},
    "source": [
-    "Solve for the Weighted Least Squares position estimate simply by passing the measurement data."
+    "Solve for the Weighted Least Squares position estimate simply by passing the measurement data.\n",
+    "\n",
+    "When obtaining WLS estimates for real measurements, the rotation of the Earth between the signal transmission and reception has to be accounted for.\n",
+    "`solve_wls` accounts for this by default and rotates the given SV positions into the ECEF frame of reference when the signals were received.\n",
+    "\n",
+    "In case you assume that the satellite positions are given for the ECEF frame of reference when the signals were received,\n",
+    "this can be accomplished by setting the parameter `tx_time = False` in the function call."
    ]
   },
   {
@@ -45,7 +51,9 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "state_wls = glp.solve_wls(derived_data)"
+    "state_wls = glp.solve_wls(derived_data)\n",
+    "# When assuming that SV positions are given in the ECEF frame when signals are received use\n",
+    "# state_wls = glp.solve_wls(derived_data, use_tx_time=True)"
    ]
   },
   {
@@ -101,7 +109,35 @@
    "id": "0387e03e",
    "metadata": {},
    "source": [
-    "Solve for the Weighted Least Squares position estimate simply by passing the measurement data."
+    "Solve for the Weighted Least Squares position estimate simply by passing the measurement data.\n",
+    "\n",
+    "The implemented EKF also assumes that the satellite positions are given for when the signals were transmitted and that\n",
+    "they must be rotated to account for the change in the ECEF frame of reference.\n",
+    "\n",
+    "In this case, to change this default behaviour, pass a dictionary `init_dict` with the key-value pair `\"use_tx_time\": True`."
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "31e7b493",
+   "metadata": {},
+   "source": [
+    "To prevent accidental usage of untuned process and measurement noises, `solve_gnss_ekf` requires an initialization \\\n",
+    "dictionary containing values for the process noise `\"Q\"` and the measurement noise `\"R\"`.\n",
+    "\n",
+    "In the naive implementation, the noise matrix is set to the size of the measurement vector using the scalar value `\"R\"`."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "2dfb8d75",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "import numpy as np\n",
+    "init_dict = {\"Q\": np.eye(7),\n",
+    "             \"R\" : np.eye(1)}"
    ]
   },
   {
@@ -113,7 +149,7 @@
    },
    "outputs": [],
    "source": [
-    "state_ekf = glp.solve_gnss_ekf(derived_data)"
+    "state_ekf = glp.solve_gnss_ekf(derived_data, init_dict)"
    ]
   },
   {
@@ -209,6 +245,14 @@
    "source": [
     "figs = glp.plot_metric_by_constellation(galileo_data, \"gps_millis\", \"residuals_m\")"
    ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "fdc6d9cb",
+   "metadata": {},
+   "outputs": [],
+   "source": []
   }
  ],
  "metadata": {