Understanding Log File Types

[Niels Joubert]

Can someone clarify all the different logging formats we have going on? 

It appears we have .tlog, .log and .bin. 

I'm using the .bin files copied from my Pixhawk's SD card to do data analysis on using mavgraph. 

What is the format of this, and how does this different from .log files? Is it .bin or .log that is implemented in the DataFlash library?

Thanks guys! I searched around, and since I couldn't find a description, I thought I'd ask.

-Niels

[Craig Elder]

.tlogs are what is transmitted via telemetry telemetry logs

.logs and .bin are what is stored locally on the autopilot and also known as dataflash logs

.log and .bin contain the same data one in a text format and one in a binary format

.log is the original format of the dataflash converted to text and .bin is a new format used on the PX4/Pixhawk. It is the raw binary data stored on the SD card. 

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[Andrew Tridgell]

Hi Niels,

I'm guessing you are analysing log files for Piksi tests. You may find
the new --dualgps option to mavflightview.py in MAVProxy useful. It
shows a map view of both GPS tracks if you have two GPS modules
connected to the aircraft.

Here is a dual-GPS log from today:

http://uav.tridgell.net/Meridian/logs/2014-03-06/log61.bin

that used two identical 3DR uBlox GPS modules. You may get slightly
different results as you have SBAS in the US, but at least with
mavflightview.py you can quickly zoom in on any differences.

You can also use mavgraph to analyse GPS differences. For example:

mavgraph.py --marker=. log61.bin 'gps_velocity_df(GPS).y' 'gps_velocity_df(GPS2).y' 'gps_velocity_df(GPS).y-gps_velocity_df(GPS2).y:2'

that shows you the Y velocity (velocity east in ground frame) from the
two GPS modules, along with the difference in velocity on the right
axis. Very useful for getting an idea of the velocity consistency.

if you are using mavproxy you can download the .bin logs over USB
without pulling the SD card out using "log list" and "log
download". Downloads run at about 170kbytes/sec. Use "log status" to see
the status of a download.

Cheers, Tridge

[Niels Joubert]

Thanks Tridge, Craig!

On top of the Piksi work, I'm also busy quantifying my battery
performance and barometer noise (attempting to improve my 7 minute
flight time on the X8 w 5000mAh lipos).

I ended up using the pymavlink.DFReader class to analyze these log
files in an IPython Notebook - my preferred way of doing exploratory
coding and data analysis. In the spirit of sharing data and results,
attached is my battery's drain curve, and the Pixhawk's barometer
output during the battery test. The battery drain test was performed
by bolding the x8 onto the desk, and running it at 10% throttle until
failsafe.


-Niels