Can I Fly uses real weather data combined with established atmospheric science to estimate wind conditions at every altitude in your drone's flyable range, not just at the surface. This page explains where our data comes from and how we work out gust speeds above 10m.
Where the data comes from
We pull weather data from two sources:
- Open-Meteo — an open-source weather API that aggregates multiple numerical weather prediction (NWP) models. It provides current and hourly forecasts including wind speed at 10m, 80m, and 120m above ground, as well as wind gusts at 10m.
- Apple WeatherKit (where available) — provides radar-fused point-in-time precipitation data, which is significantly more accurate than model-based precipitation estimates for detecting whether it is actually raining right now.
Why we only get gusts at 10m
Consumer and commercial weather APIs, including Open-Meteo, WeatherKit, and Windy, only provide measured gust data at surface level (10m). Gust measurements at 80m, 100m, or 120m are simply not available from any public weather service at any altitude above the surface. This is not a limitation of Can I Fly specifically — it applies universally. Any app, website, or tool that displays gust speeds above 10m is deriving those figures from a calculation, not a measurement. The methodology may differ, but the principle is the same.
This is because gusts are caused by short-lived turbulent fluctuations in the boundary layer close to the ground. Higher up, the airflow becomes more laminar (smoother), so gusts are less intense relative to the mean wind speed. There is no widely available sensor network or forecast product that measures gusts at low drone-flying altitudes.
How we estimate gusts at altitude
Since gust data above 10m is unavailable, we estimate it using a physically grounded model based on Turbulence Intensity (TI), a standard metric in atmospheric boundary layer science and the wind energy industry.
Turbulence Intensity describes the ratio of wind speed variability to mean wind speed. Research consistently shows that TI decreases with height:
- At 10–20m: TI is typically 15–20%, meaning gusts can be 1.30–1.40x the mean wind
- At 80m: TI drops to around 10–12%, giving a gust ratio of roughly 1.15–1.18x
- At 100m+: TI is typically 8–10%, giving a gust ratio of around 1.10x
This behaviour is documented in the IEC 61400-1 wind turbine design standard and the ESDU 85020 atmospheric boundary layer profile, both widely used in wind energy and aerospace engineering.
In Can I Fly, we apply this by taking the real measured gust ratio at 10m and tapering it linearly down to 1.10x at 120m. So if ground-level gusts are 1.35x the mean wind, we'd estimate roughly 1.25x at 40m, 1.18x at 80m, and 1.13x at 100m.
How we use this in the flyability decision
We build an altitude profile for every check, evaluating wind and estimated gusts at 10m, 20m, 40m, 60m, 80m, 100m, and 120m. Each level is assessed against your drone's maximum wind resistance:
- Within limits: wind is below 65% of the drone's maximum
- Approaching limits: wind is between 65% and 85% of the maximum
- Beyond limits: wind or estimated gusts exceed 85% of the maximum, or gusts breach the drone's absolute hard limit at any altitude
The gust check at ground level (10m and 20m) uses the real measured gust figure. Above 20m, the beyond-limits check uses the tapered estimate. If estimated gusts at any altitude breach the drone's hard maximum, that altitude is flagged as beyond limits regardless of the sustained wind.
The overall result can also show Caution for conditions unrelated to wind, such as flying after dark. In these cases the wind profile may be within limits, but local regulations or visibility conditions mean it is the pilot's responsibility to verify whether flying is permitted. The app flags these situations but does not make the decision for you.
Is this accurate?
The tapered model is physically realistic and more accurate than applying a flat gust ratio at all heights. It will, however, remain an estimate — no consumer weather product provides real gust measurements above 10m.
When Apple WeatherKit credentials are configured, precipitation accuracy improves significantly. Wind accuracy at altitude is limited by what the underlying forecast models resolve, which is typically accurate to within 1–2 m/s for the forecast period.
We err on the side of caution. If the estimated gusts at altitude suggest conditions are borderline or worse, we will tell you, even if the sustained wind is within limits.