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Merge pull request #559 from dronekit/flight-replay-localfile
Rejig flight replay example to use a telemetry log peter.barker 5:08 PM All looks good to me. You OK if I merge that one? hamishwillee 5:08 PM Yes please!
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‎docs/examples/flight_replay.rst‎

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=========================
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======================
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Example: Flight Replay
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=========================
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======================
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This example requests a past flight from Droneshare, and then writes the recorded path to the vehicle as mission waypoints.
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For safety reasons, the altitude for the waypoints is set to 30 meters (irrespective of the recorded height).
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This example creates and runs a waypoint mission using position information from a TLOG file.
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.. note::
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The log used in this example contains around 2700 points. This is too many points to upload
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to the autopilot (and to usefully display). Instead we only add points that are more than
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3 metres away from the previously kept point, and only store 99 points in total.
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After 60 seconds the mission is ended by setting the mode to RTL (return to launch).
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The mission is not actually run by this code - though it easily could be by taking off and putting the vehicle into
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AUTO mode.
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.. figure:: flight_replay_example.png
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:width: 50%
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99 point mission generated from log
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You can specify which mission to replay using a parameter when starting the script (for example, to replay your own local flights).
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By default the code gets the public `Droneshare mission with ID 101 <http://www.droneshare.com/mission/101>`_.
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.. figure:: flight_replay_example.png
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.. note::
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Droneshare Mission #101
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The method used to reduce the number of points is fairly effective, but we
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could do better by grouping some of the waypoints, and mapping others using
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spline waypoints. This might be a
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`fun research project <https://github.com/dronekit/dronekit-python/issues/561>`_!
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The example can be run as described in :doc:`running_examples` (which in turn assumes that the vehicle
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and DroneKit have been set up as described in :ref:`installing_dronekit`).
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If you're using a simulated vehicle, remember to :ref:`disable arming checks <disable-arming-checks>` so
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that the example can run.
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In summary, after cloning the repository:
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#. Navigate to the example folder as shown:
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.. code-block:: bash
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cd dronekit-python/examples/flight_replay/
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#. Start the example, passing the :ref:`connection string <get_started_connect_string>`
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you wish to use in the ``--connect`` parameter and specifying the mission to replay.
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#. You can run the example against a simulator (DroneKit-SITL) by specifying the Python script without any arguments.
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The example will download SITL binaries if needed, start the simulator, and then connect to it:
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.. code-block:: bash
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python flight_replay.py --connect 127.0.0.1:14550 --mission_id 101
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python flight_replay.py
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.. note::
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On the command prompt you should see (something like):
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The ``--connect`` parameter above connects to SITL on udp port 127.0.0.1:14550, while
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``--mission_id`` specifies we're replaying mission 101. Both of these are the default
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values for the parameters, and may be omitted.
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.. code:: bash
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Generating waypoints from tlog...
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Generated 100 waypoints from tlog
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Starting copter simulator (SITL)
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SITL already Downloaded.
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Connecting to vehicle on: tcp:127.0.0.1:5
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>>> APM:Copter V3.3 (d6053245)
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>>> Frame: QUAD
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>>> Calibrating barometer
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>>> Initialising APM...
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>>> barometer calibration complete
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>>> GROUND START
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Uploading 100 waypoints to vehicle...
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Arm and Takeoff
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Waiting for vehicle to initialise...
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>>> flight plan received
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Waiting for arming...
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Waiting for arming...
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Waiting for arming...
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Waiting for arming...
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>>> ARMING MOTORS
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>>> GROUND START
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Waiting for arming...
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>>> Initialising APM...
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Waiting for arming...
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>>> ARMING MOTORS
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Taking off!
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Altitude: 0.000000 < 28.500000
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Altitude: 0.010000 < 28.500000
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...
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Altitude: 26.350000 < 28.500000
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Altitude: 28.320000 < 28.500000
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Reached target altitude of ~30.000000
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Starting mission
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Distance to waypoint (1): 3.02389745499
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>>> Reached Command #1
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Distance to waypoint (2): 5.57718471895
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Distance to waypoint (2): 4.1504263025
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>>> Reached Command #2
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Distance to waypoint (3): 0.872847106279
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Distance to waypoint (3): 1.88967925144
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Distance to waypoint (3): 2.16157704522
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>>> Reached Command #3
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Distance to waypoint (4): 4.91867197924
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...
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...
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Distance to waypoint (35): 4.37309981133
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>>> Reached Command #35
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Distance to waypoint (36): 5.61829417257
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>>> Reached Command #36
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Return to launch
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Close vehicle object
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Completed...
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.. tip::
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It is more interesting to watch the example run on a map than the console. The topic :ref:`viewing_uav_on_map`
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explains how to set up *Mission Planner* to view a vehicle running on the simulator (SITL).
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.. tip::
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It is more interesting to watch the example above on a map than the console. The topic :ref:`viewing_uav_on_map`
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explains how to set up *Mission Planner* to view a vehicle running on the simulator (SITL).
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#. You can run the example against a specific connection (simulated or otherwise) by passing the :ref:`connection string <get_started_connect_string>` for your vehicle in the ``--connect`` parameter.
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On the command prompt you should see (something like):
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For example, to connect to SITL running on UDP port 14550 on your local computer:
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.. code-block:: bash
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Connecting to vehicle on: 127.0.0.1:14550
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>>> APM:Copter V3.3 (d6053245)
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>>> Frame: QUAD
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JSON downloaded...
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Generating 95 waypoints from replay...
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Close vehicle object
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Completed...
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.. code-block:: bash
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python simple_goto.py --connect 127.0.0.1:14550
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How it works
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============
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The example requests the web server for representative points from the flight, parses the JSON response
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and uses that data to generate 100 waypoints. These are then sent to the vehicle.
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Getting the points
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------------------
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The following simple function asks for the droneshare flight data:
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The example parses the **flight.tlog** file for position information. First we read all the points.
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We then keep the first 99 points that are at least 3 metres separated from the preceding kept point.
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.. code:: python
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For safety reasons, the altitude for the waypoints is set to 30 meters (irrespective of the recorded height).
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def download_messages(mission_id, max_freq = 1.0):
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"""Download a public mission from droneshare (as JSON)"""
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f = urllib.urlopen("%s/api/v1/mission/%s/messages.json?max_freq=%s&api_key=%s" % (api_server, mission_id, max_freq, api_key))
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j = json.load(f, object_hook=_decode_dict)
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f.close()
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return j
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.. code:: python
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Some comments:
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def position_messages_from_tlog(filename):
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"""
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Given telemetry log, get a series of wpts approximating the previous flight
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"""
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# Pull out just the global position msgs
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messages = []
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mlog = mavutil.mavlink_connection(filename)
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while True:
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try:
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m = mlog.recv_match(type=['GLOBAL_POSITION_INT'])
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if m is None:
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break
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except Exception:
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break
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# ignore we get where there is no fix:
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if m.lat == 0:
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continue
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messages.append(m)
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# Shrink the number of points for readability and to stay within autopilot memory limits.
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# For coding simplicity we:
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# - only keep points that are with 3 metres of the previous kept point.
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# - only keep the first 100 points that meet the above criteria.
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num_points = len(messages)
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keep_point_distance=3 #metres
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kept_messages = []
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kept_messages.append(messages[0]) #Keep the first message
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pt1num=0
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pt2num=1
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while True:
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#Keep the last point. Only record 99 points.
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if pt2num==num_points-1 or len(kept_messages)==99:
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kept_messages.append(messages[pt2num])
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break
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pt1 = LocationGlobalRelative(messages[pt1num].lat/1.0e7,messages[pt1num].lon/1.0e7,0)
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pt2 = LocationGlobalRelative(messages[pt2num].lat/1.0e7,messages[pt2num].lon/1.0e7,0)
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distance_between_points = get_distance_metres(pt1,pt2)
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if distance_between_points > keep_point_distance:
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kept_messages.append(messages[pt2num])
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pt1num=pt2num
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pt2num=pt2num+1
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return kept_messages
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* ``max_freq`` is used to throttle the messages found in the raw flight data to a lower message rate
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* ``_decode_dict`` is a utility function found on stack overflow which extracts usable strings from unicode encoded JSON (see `flight_replay.py <https://github.com/hamishwillee/dronekit-python/blob/master/examples/flight_replay/flight_replay.py>`_ for its implementation).
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Setting the new waypoints
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-------------------------
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If necessary, the example then reduces the number of messages retrieved into a set that can fit on the vehicle (in this case 100 waypoints).
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The following code shows how the vehicle writes the received messages as commands (this part of the code is very similar to that
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shown in :ref:`example_mission_basic`):
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‎docs/examples/flight_replay_example.png‎

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‎examples/flight_replay/flight.tlog‎

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