Angle Units Worldwide

While most of the world uses degrees for everyday angle measurement, different fields and regions use various systems. 変換元 the ancient Babylonian 360-degree circle to modern radians for calculus to military mils for artillery, each system serves specific purposes.

度: The Universal Standard

Characteristics

• Full circle = 360°
• Right angle = 90°
• Origin: Babylonian (~2000 BCE)
• Subdivisions: 分 (') and seconds (")

Global Usage

• Everywhere: General measurement, education
• Navigation: Compass bearings worldwide
• Geography: Latitude and longitude
• Construction: Building angles globally
• Aviation: Runway headings, flight paths

Why 360?

Chosen by Babylonians because 360 is highly divisible (by 2, 3, 4, 5, 6, 8, 9, 10, 12, 15, 18, 20, etc.) and close to the number of days in a year.

ラジアン: The Mathematical Standard

Characteristics

• Full circle = 2π ≈ 6.283 radians
• Right angle = π/2 ≈ 1.571 radians
• 1 radian ≈ 57.3°
• Origin: Mathematical (18th century)

Primary Usage

• Mathematics: Calculus, trigonometry worldwide
• Physics: Angular velocity, circular motion
• Engineering: Signal processing, control systems
• Programming: Most math libraries default to radians

Why ラジアン in Math?

ラジアン make calculus formulas simpler: d/dx sin(x) = cos(x), and arc length = radius × angle (only in radians).

グラジアン (Gons): Metric Angles

Characteristics

• Full circle = 400 gradians
• Right angle = 100 gradians
• 1 gradian = 0.9°
• Origin: French Revolution (1790s)

Usage

• France: Some surveying and mapping
• Germany, Switzerland: Land surveying
• Other European countries: Limited surveying use

Why 400?

Created as part of メートル法 reform—makes percentages easy (1% grade = 1 gradian). A right angle is exactly 100, making decimal arithmetic simpler. Never achieved widespread adoption outside surveying.

Military Mils: Artillery Standard

Different Mil Systems

Why Mils?

At 1 kilometer distance, 1 NATO mil subtends approximately 1 meter. This makes range and deflection calculations simple for artillery:

• Target 5 mils wide at 2 km = 10 meters wide
• Adjust fire by mils, calculate distance in meters

Other Angle Units

Turns (回転)

• 1 turn = 360° = 2π radians
• Used in engineering for counting rotations
• Intuitive for complete circles

Hour Angle

• Used in astronomy
• 24 hours = 360° (1 hour = 15°)
• Relates Earth's rotation to celestial observation

Points (Compass)

• 32 points = full circle
• 1 point = 11.25°
• Traditional maritime navigation
• "North by northeast" = 1 point east of north

Binary 度 (Brads)

• 256 brads = full circle
• Used in some computer graphics
• Fits in one byte, allows fast bit operations

Regional Preferences

International Standards

• SI (official): ラジアン for plane angles
• ISO 31-1: Accepts degrees, radians, gradians

By Application

Conversion Reference

まとめ

While degrees remain the universal everyday angle unit, different fields require different systems. ラジアン dominate mathematics and physics because they simplify calculus. グラジアン persist in some European surveying. Military organizations use various mil systems for artillery calculations. 理解する these systems—and being able to convert between them—is important for international technical work and specialized applications.

関連記事

• 度 vs ラジアン: When to Use Each Angle Unit
• の歴史 Angle Measurement: 変換元 Ancient Astronomy to Modern Engineering