Douglas Square Protractor — 10″ (250 mm)
Classic Navigational Protractor • Plotter & Parallel Rule in One
The Douglas Square Protractor 10″ (250 mm) is a versatile, traditional navigation instrument designed for accurate chartwork at the chart table. Based on the proven Douglas-type square pattern, it enables quick, reliable bearing plotting while also serving as a simple parallel rule and plotter—making it an efficient all-in-one tool for manual navigation.
Clear markings and a generous working size make it especially well suited to coastal and offshore chart use, training environments, and backup navigation kits.
🧭 Key Features
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📐 Douglas-type square pattern — a time-tested format for precise bearing transfer
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📏 10″ (250 mm) length — ideal for full-size nautical charts and plotting sheets
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🗺️ Multi-purpose tool — functions as a protractor, simple parallel rule, and plotter
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⚓ Designed for chart tables — stable, readable, and easy to align on paper charts
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📦 Practical & durable — built for repeated use in navigation and instruction
⚓ Why Navigators Choose the Douglas Square
The Douglas square format is valued for its simplicity and speed. Bearings can be laid off directly, then transferred across the chart without switching tools—ideal when plotting fixes, courses, or clearing lines under time pressure or when electronics are unavailable.
📐 Specifications
| Specification | Details |
|---|---|
| Type | Douglas-type square navigational protractor |
| Length | 10″ (250 mm) |
| Alternate Size | Also available in 5″ (130 mm) |
| Functions | Protractor, simple parallel rule, plotter |
| Use | Nautical chart plotting & navigation |
🎯 Ideal For
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⛵ Sailors & offshore cruisers
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🧭 Navigation students & instructors
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📚 Manual chart plotting & course setting
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🧰 Backup navigation kits
The Douglas Square Protractor 10″ (250 mm) is a reliable, no-nonsense chartwork essential—accurate, versatile, and rooted in traditional seamanship.
Add a proven plotting tool to your navigation kit and work confidently at the chart table.
