Building in the open
What would your logbook need to prove?
BlueLogbook takes your GPS track and cross-checks it against satellite weather and tide data. It works — there's a live example below. What we don't know yet is who actually needs it, and what for. Tell us, and we'll build toward that.
It already works
Upload a GPX track. We pull ERA5 wind, wave and tidal current data for the exact times and positions you sailed, check your track against them, and issue a certificate with a public link anyone can open.
Every rule we score against is published. Every deduction is shown, including the ones that count against you.
See a real certificate — a Channel crossing scored 84 out of 100, with three discrepancies listed.