This week, we’re going back to take a look at logs. In Quick Tip #7, we talked about making sure you record a log whenever you execute a mission. This week, we’re going to talk about what’s in a log file and how you can get specific data out of one.
What’s in a Log?
Whenever you take a log in Workspace, the system is recording all of the signal data that Workspace observed. All of this is recorded in the telemetry file. In addition, Workspace also records the video and sonar feeds if your vehicle has them. By default, these files are stored in the gss_logs folder on your computer.
We’re going to do some slight handwaving here, but OPENSEA uses LCM (Lightweight Communications and Marshalling) to send information across the system. Sensors and devices produce data get sent to OPENSEA applications, these applications transmit data as signals that are sent on a specific channel. The telemetry log file is a record of all of the data that was generated and observed by Workspace while you were taking a log. This is why you can interact with Playback Workspace while you’re replaying a recorded log.
But, you can do more with the telemetry file than just play back a log. You can extract specific channel information from a log file to do more advanced diagnostics.
Creating a CSV from a Log
Open Workspace (or Playback Workspace depending on your version). In Mission Panel Tools, open the Logging tab and click the Convert subtab. Click the Choose Log File button and use the file viewer to select a telemetry file. When you select a file, you’ll get a list of all the channels Workspace recorded in that log file. Choose the channel (or channels) you want to extract data from, and hit the Convert button.
Workspace will create a CSV file of all the data that came through that channel and save it in the same folder as your telemetry file. Now, you can then use that in an external program like MATLAB to analyze it in depth.
As always, thank you for continuing to check out our quick tips. Next week, we’ll be getting back into vehicle control and talking about autopilot jogs. But, we are always taking requests! If there’s something you’d like to see a quick tip for, contact us at firstname.lastname@example.org Have a great week!