Trajectory Forecasts

Trajectory forecasts show predicted wind paths at multiple altitudes, giving you a visual indication of where the wind will carry a balloon over the next few hours. This is similar to the trajectory feature in Windy.com.

How It Works

Starting from a position on the map:

1. The app fetches wind forecast data from Open-Meteo for multiple altitude levels
2. At each time step, it calculates where the wind would carry a balloon
3. The resulting paths are drawn on the map as coloured lines — one per altitude level

Each trajectory shows the wind path for a specific altitude (e.g., surface, 2000 ft, 3000 ft), giving you a vertical view of how wind patterns differ with height.

Using Trajectories

1. Tap the trajectory settings button (right side of screen)
2. Configure the forecast:
   • Starting position — defaults to your current location
   • Altitude levels — select which heights to forecast
   • Weather model — choose from available forecast models
3. Tap to generate the forecast
4. Trajectories appear on the map as coloured paths

Forecast Models

Open-Meteo provides several weather forecast models. The model selector lets you choose which one to use. Different models may give slightly different results depending on the region and conditions.

Altitude Levels

You can select which altitude levels to include in the forecast. Each level generates a separate trajectory line in a different colour, making it easy to see how wind varies with height.

Trajectory Colours

Each altitude level is drawn in a distinct colour. The colour can be customised via the colour picker in trajectory settings.

Time Steps

The forecast advances in time steps (e.g., 10 minutes), fetching new wind data at each point along the trajectory. The total forecast duration covers several hours of flight time.

API Quota

Trajectory forecasts use the Open-Meteo API. API calls count against a daily quota to comply with the fair-use policy. The remaining call count is shown in settings.

A progress indicator appears while the forecast is being calculated, as multiple API calls may be needed.

Limitations

• Forecasts are based on weather model predictions, which are inherently uncertain
• Wind conditions can change rapidly and may differ from the forecast
• Trajectories assume passive drift (no powered flight or active altitude control)

Note

Attribution: Weather forecast data is provided by Open-Meteo. Open-Meteo provides free weather APIs for non-commercial use.