A wind sounding with no provider: wind profile from thermal drift

When you circle in a thermal, the thermal drifts with the air mass. You draw circles inside it, but the centre of those circles moves downwind. That drift is the wind at that altitude.

How it's computed

For each thermal, the displacement of the circling centroid between its early and late portions is measured:

• Displacement ÷ elapsed time = wind speed
• Direction of the drift = where the wind is going → the reciprocal = where it comes from (meteorological)

Thermals at different altitudes are reduced into 200-metre bands to build a wind sounding from a single flight — typically 500–3000 m.

Why it's valuable

• No weather provider needed. The data comes straight from your track.
• Real, local wind. Not a model forecast, but what actually happened in that valley that day.
• XC planning. Seeing how the wind veers with altitude feeds your route decisions.

Limits

The measurement needs the pilot to actually circle; on short or ridge-type climbs the result is sparse. Without enough circling, the Variograph panel simply doesn't show — it never fabricates values. The resolution is set by the track's sampling rate — see IGC data quality for the details.

Where in Variograph

The Wind Profile panel in Advanced Analysis → Overview shows a direction arrow and speed table per altitude band. The air climb figures for the same thermals sit in the table next to it; you manage your takeoff spots and flight archive from the dashboard.