Logs

On each launch, the server creates a log of all the messages sent by the aircraft. This log can be used to analyse flight data and to replay the flight.

Format

The log files are stored in the var/logs/ folder (under PAPARAZZI_HOME). A log is split into two files:

• A .log file, an XML file, which contains a copy of the whole configuration (airframes, flight plans, ...).
• A .data file, an ascii file, which contains the list of the received messages. Each message is time-stamped in seconds since the creation of the file and marked with the id of the sending aircraft.

The basename of these two files is the same and is build from the date and time at the creation.

The lines of the .data file are formatted according to the message description listed in the conf/messages.xml file. For example, the following line:

3.300 6 GPS 3 36028551 481359212 899 18500 0 -8 960 31 0

contains a GPS message received at time 3.3s, from aircraft 6. According the GPS message description:

<message name="GPS" ID="8">
    <field name="mode"   type="uint8" unit="byte_mask"></field>
    <field name="utm_east"  type="int32" unit="cm"></field>
    <field name="utm_north"  type="int32" unit="cm"></field>
    <field name="course" type="int16" unit="decideg"></field>
    <field name="alt"    type="int32" unit="cm"></field>
    ...
</message>

UTM position is 360285.51m east, 4813592.12m north, course is 89.9° (east), altitude is 185m, ... Note that the appropriate messages.xml description, i.e. the one which has been used while the log was created, is itself stored in the associated .log file. It may differ from the current one installed in your conf/ folder.

Note: The .data files may be huge (about 4M per hour with a standard telemetry configuration). They can be efficiently compressed. The tools described in the next sections handle most of the compressed format (.zip, .gz, .bz2, ...). The bzip2 compression seems to perform better than others on these files.

Data Plotting

Data stored in log files can be plotted with the Plotter (sw/logalizer/plot or launchable from the Paparazzi Center). This tool can plot data from different logs in the same window and data from the same log in different windows. It also offers to export the track as a KML file for Google Earth.

Replay

A flight can be replayed with the Log Flight Player (sw/logalizer/play, launchable from the Paparazzi Center). This agent then is a substitute for the Data Link agent and will send over the bus the messages which had been send by the aircraft while the log was recorded.

Note: While replaying a log, it is a good idea to disable a new log creation from the server (-n option).

When doing a log replay it is very valuable to launch the messages window (in the tools menu) as well. This allows for the use of the the real time plotter and also gives the data from the aircraft to the user.

If the user wishes to speed up a replay gaia can be used (launch from paparazzi centers tools menu) to do this by changing the time scale.

A .log file given in the command line will be loaded on startup.

Output on a serial port

Launched with the -o option, the player will send to a serial port all the binary messages, as they have been received through the modem during the flight. Related options:

• -s Set the baudrate (9600)
• -d Set the device (/dev/ttyUSB0)

Load PprzLog into Matlab Workspace

Paparazzi log file could also be converted into matrices in matlab workspace for further data processing. An example matlab script is shown in PprzLog2Matlab_1_0.zip. The example script needs the inputs of the log file name and directory. Just modify the line "fid = fopen('.\FlighLog20090321_MZN\09_03_19__15_03_14.data','r');". Eight matrices are read into matlab workspace including GPS_SOL, GPS, PPRZ_MODE, DESIRED, ATTITUDE, NAVIGATION, NAVIGATION_REF, COMMANDS. The user could also modify the code easily to add more messages they want to know.

The logviewer GUI

There is now another parser named log2struct available, see this post on the mailing list. It does not require code modification and can read any messages sent from any aircraft. Usage examples can be found in the source code documentation.

A GUI built on this parser is available: Logviewer.zip. It is based on the GUI from sw/logalizer/matlab_log but features some improvements, e.g. in speed and reliability. Standard plots like trajectory, attitude or speed are available for quick reviewing and Matlab's plotting tools can be accessed for plot cosmetics and printing.