I’ve been working with some telemetry from a test dive, as the ability to record and download ROV telemetry data is a must for any scientific exploration. However, I have found that there are few resources available through the OpenROV support forums that explain how to access and use these data. I have written up a short protocol, which can be found below.
- As you set up the ROV for startup, make sure you orient the nose northward. The compass cannot determine magnetic north, and therefore takes its 0-degree calibration from its position upon startup.
- During the dive, make sure that telemetry is recording in the cockpit GUI. The Download button should be clickable and the recording light green.
- Once you have finished recording telemetry data, click Download and a .json file will be downloaded through your browser. If you open this file in a text editor or in Excel, you will see it is a form of a comma separated text file. As is, Excel cannot interpret individual data values for each parameter (pitch, yaw, depth, etc.) and therefore it must be separated.
- The fastest way I have found to do this is to use an online .json to .csv converter, such as http://konklone.io/json/. This will interpret the code into headers (or columns), with each parameter value separated by a comma.
- Copy all of your data into an Excel spreadsheet. Only the first column will contain data, which are each of the parameter values at a particular timestep.
- Highlight the first column, then navigate to Data, Text to Columns. Select Delimited, Next, deselect Tab and select Comma, Next, General, Finish. Each parameter should now have its own column.
- Next, you need to line up the telemetry data feed with your recorded video. The timestamp in the dataset is in milliseconds from initial startup and matches with the timestamp shown in your full screen video recording. From there, you can convert it to real time or elapsed time based on your computer’s time at ROV startup.
- From there, you can do any kinds of analyses on your ROV telemetry parameters. I suspect you can create a rough bottom profile of a feature of interest by “mowing the lawn” (parallel linear transects) and then plotting depth over time.
I would love to see others take this further and post any attempts, suggestions, modifications!