How we estimate sun and shade

Sunny terraces estimates whether a terrace gets sun by combining the sun's position at each moment with the height of the surrounding buildings. All the calculation happens in your browser.

Diagram: the sun's position and building heights determine sun or shade — A building's shadow depends on the building's height and how low the sun is.

1. The sun's position

For the chosen date and time, and for the location you are looking at, we calculate the sun's height above the horizon and its bearing (where the light comes from). At sunrise and sunset the sun is low and shadows are long; at midday it is high and shadows are short.

2. Building heights

We use public building data with their approximate heights. With the building height and the sun's angle we work out how far its shadow reaches and whether that shadow falls on the terrace.

3. Sun or shade for each terrace

We cross the projected shadows with the position of each licensed terrace. If no shadow covers it, we mark it as sunny; if it is covered, as shaded. You can change the time to see how it evolves through the day.

What is and isn't an estimate

Positions are estimated from the nearest outer façade; they are not real on-the-ground observations.
The shadow calculation does not account for trees, awnings or canopies.
Building heights come from open data and may not be up to date in detail.

It's a quick guide for deciding where to sit, not an exact measurement.

Your location never leaves your device

If you grant location permission, it is used only in your browser to centre the map: it is never sent to our servers or to third parties. You'll find more details on the privacy page.