Analyzing your Expedition Sailing Data in Tableau

Expedition and Tableau are both leading software products and joining them to analyze your sailing data to improve your performance or yacht setup seems like a natural fit. With this blog you should be able to use your data and build a Tableau Viz for analysis in no time.

Tools:

• Expedition to log your instrument data.

• Optional: python to preprocess your logs.

• Use Tableau Public to analyze your data. “This is free software and allows you to share the data with your partners and crew.”

Background

Expedition stores log files by day and you can select what data is saved. However, in recent versions of Expedition the log files are not true CSV files anymore. They are sparse with an index number that represents the field, and in this form are not ready to import into a database or analysis program like Tableau.

Your Options:

• You can export your data by loading the log file in Expedition and exporting to CSV.

• You can use other software to parse and clean up the data. I chose this latter option and created a free-to-use python script to stitch multiple days of Expedition logs together. You can use this on your data: Github Script.

  Some advantages of this program:

  • It can clean up data and detect tacks and gybes and mark windows of data around these events.

  • It can join in your polar files and your target data for polar analysis.

Expedition stores times as a floating-point number that is in Excel Epoch time, so you will need to convert this to a time format that is understood by other systems. The formula for converting in Tableau is provided below.

• Getting it done:

• Place all the log files in one directory. Use the python code above to clean and join the data into one CSV file.

• Load your CSV file into Tableau.

• Create a calculated field for timestamp in Tableau, with the formula “DATETIME([Utc] + INT(#December 30, 1899#))”

• Right click on the Lat and Lon data fields and change the type to geographic then select latitude and longitude respectively. You can now plot your track \ positions on a map.

• Plotting Polars as a radial can be harder. You need the formulas to convert boat speed vector at a TWA to an X / Y coordinate for a scatter. Create 2 calculated fields:

  • RadialX = [BSP]*cos(RADIANS([TWA (Abs)]))

  • RadialY = [BSP]*sin(RADIANS([TWA (Abs)]))

An example of this all pulled together is here on the web: Tableau Viz of the Globe 40 Leg2 data

If you would like help with any sailing data, feel free to reach out to us and we can help you on your data analysis and sailing journey.