The method
Before using the result
- Vertical object, level horizontal receiving surface and supplied solar altitude above the horizon. Sun azimuth and location/time are not solved.
Worked examples
These original training examples illustrate the method for First-Class Architect Exam 一級建築士 (Gakka Written + Design Drafting). Use the matching “Load example” button above to explore a variation; example values are not equipment settings or prescribed criteria.
1. Worked example
Connect a supplied solar altitude to the shadow of a vertical object on a horizontal plane. This is a geometry exercise, not a site solar-position model.
- Object height
- 5 m
- Supplied solar-altitude angle
- 45 °
- Shadow = 5 / tan(0.7853981633974483 rad) m.
- Horizontal shadow: 5 m
2. Comparison example
Compare a different supplied condition using the same method. For Kenchikushi Exam, the important check is that the input meaning, units and method assumptions still match the problem.
- Object height
- 5 m
- Supplied solar-altitude angle
- 30 °
- Shadow = 5 / tan(0.5235987755982988 rad) m.
- Horizontal shadow: 8.660254 m
Check your understanding
1. Which relationship is used?
Horizontal shadow length = object height / tan(solar altitude).
2. Which assumption should you check first?
Vertical object, level horizontal receiving surface and supplied solar altitude above the horizon. Sun azimuth and location/time are not solved.
3. How should you verify a different unit system?
Convert every input to the displayed calculation units first. Equivalent physical inputs must give equivalent results; a unit label alone does not convert a number.
Continue with the matching exam topic
This tool connects to First-Class Architect Exam 一級建築士 (Gakka Written + Design Drafting) free practice. Work through a question independently, then use the calculation steps to identify where your method differs. The tool stays free whether or not you choose paid preparation.