Earth and space context
Earth context, calculated by country
Not every useful country figure comes from a survey. Day length is calculated from latitude, longitude, and date, then shown on the same map as observed and modelled public data.
The method is public: a representative coordinate for each UN member state, a stated formula, and sunrise/sunset notes in UTC. It is an estimate of photoperiod, not a local civil timetable.
What you can compare
Hours of daylight for a selected date at each country’s representative location, with polar-day and polar-night notes where the calculation requires them.
Why it belongs in the atlas
Calculated layers sit beside observed ones so visitors can learn the difference. The map is shared. The evidence type is not.
Indicators in this theme
Each indicator keeps its own source, period, and method. Open a layer for the definition, then a country for the value.