A Simple Sailing Log Analyzer

Jul 5

Somewhere between charting courses and fixing things that probably shouldn’t break at sea, I put together a little Python utility to crunch through my GPX track logs. Nothing fancy—just a script that reads a pile of GPS data and spits out a summary: trip distances, average speeds, and rough start/end locations.

What I didn’t expect was that it would tell me a few stories I’d nearly forgotten.

What It Does

This script takes your .gpx files and turns them into something you can actually browse. It pulls out:

Start and end times
Distances in miles and nautical miles
Average moving speeds
First and last known coordinates (turned into approximate place names)
Moving time, number of segments, and more

I wrote it to analyze my own tracks from sailing aboard Eventide, but it’s generic enough to work with most GPX logs.

You can find the full code here: https://github.com/amarcuss/gpx-track-analyzer

How to Use IT

You can run the script a few different ways depending on what you want:

# Process all tracks in default file
python3 gpx_parser.py

# Process specific GPX file
python3 gpx_parser.py my_sailing_trip.gpx

# Process first 5 tracks only (for quick analysis)
python3 gpx_parser.py --max-tracks=5

# Save to custom output file
python3 gpx_parser.py --output=sailing_analysis.txt

# Export track data to CSV for spreadsheet analysis
python3 gpx_parser.py --csv=sailing_data.csv

# Combine all options for comprehensive analysis
python3 gpx_parser.py my_tracks.gpx --max-tracks=10 --output=summary.txt --csv=data.csv

The CSV export is where things get interesting. It’s clean, sortable, and surprisingly nostalgic.

What I Learned

Once I ran this across all my tracks, the results brought back a few memories—and some chuckles:

321 total voyages. Some were short hops. Others? Let’s just say “offshore character-building exercises.”
Longest trip: 509 nautical miles, from Newport, OR to Sausalito, CA. The coast was gray, the wind confused, and the coffee supply… under duress.
Shortest trip: 0.0 nautical miles. I suspect I recorded 20 minutes of dockside pondering.
Fast trip: I forgot about the time we once actually timed the tidal currents perfectly and got to Pt. Townsend from Seattle averaging over 8 knots.

A Few Favorites

What really struck me was the rhythm that emerged—quick morning hops around Puget Sound, slow drifts through glassy Baja anchorages, and long Pacific passages that felt endless at the time, but now collapse into a few lines in a spreadsheet.

Seeing “Road Town to Little Mountain” pop up made me remember that night in the BVIs when we ghosted into a calm anchorage lit only by bioluminescence and the red glow of the cockpit instruments.

Or that quick hop from Poulsbo to Keyport — a Holiday Lights parade when we nearly froze in the cockpit.

Why I Bothered

I wrote this mostly for me. After dozens of trips, the logbook gets blurry. This little tool gave me a new way to remember where we’ve been—lines and numbers that sparked real memories.

If you’re logging your own tracks, give it a go. Or write your own. That’s part of the fun.

Fair winds.

Aidan Marcuss