IGC Flight Log Analyser

What it’s for

Turns a glider flight log into a soaring debrief: how the flight split between circling and cruising, what each climb did, what the wind was, and what the air was doing on the straight legs.

How to use it

Open igc.neale.dev and drop an IGC file onto the page. The analysis appears in the tab. Nothing is uploaded, and once the page has loaded it works with the network off.

Features

• Phase split first, which decides the kind of debrief the flight gets — a day spent 15% circling isn’t graded as a thermalling flight
• Climb analysis circle by circle, showing whether centring improved, decayed or oscillated rather than just an average
• Wind from the drift of whole circles, reported with the circle count behind each estimate so you can see when it isn’t evidence
• Airmass figures for the straight legs, with polar sink for the speed and density flown taken out
• Declared tasks read from the C records and shown as a declaration — shape, legs, total — with take-off and landing records excluded, and no pretence of being a claim
• Caveats sit above the figures they affect: a coarse logger fix rate can’t show centring inside a circle, and every airmass figure is only as good as the assumed polar

How it works

Everything runs client-side. The file is read with the File API and analysed in the browser — no backend, no upload, no analytics. The analysis core is a dependency-free TypeScript port of a Python implementation, which stays in the repository as the test oracle: golden fixtures have to match it number for number, and any deliberate divergence is registered and explained.