Solar Azimuth and Altitude: A Worked Example

Latitude and longitude anchor the observer. The calendar date establishes the seasonal declination, and the IANA timezone converts the selected local clock time to the instant required by the solar-position calculation. Changing any one of these inputs can change both output angles.

The site normalizes azimuth into 0–360° clockwise from true north. Altitude remains signed: positive above the horizon and negative below it. This convention avoids the ambiguity that occurs when a bearing and an elevation are reported without definitions.

A cardinal label such as north-east is a readable summary of the numeric bearing, but the degree value is more precise. For a facade, street, or camera axis, compare the actual bearings rather than assuming every direction within one cardinal sector is equivalent.

Altitude tells you whether direct rays can clear a level horizon, but not whether they clear the real skyline. The next step is always an obstruction check.

Open the Solar Azimuth & Altitude Calculator, enter 39.742476, −105.1786, choose 17 October 2003, and select 13:30 in America/Denver. The minute-level interface should closely reproduce the evidence table; the validation registry evaluates the exact 19:30:30 UTC instant.

Keep the external expected values separate from the site result. The downloadable benchmark CSV records expected, actual, delta, tolerance, and pass/fail so a dependency upgrade can be checked without silently changing the reference.