Convert Nautical Mile (UK) (NM (UK)) to Chain (US Survey) (ch (US)) instantly.
About these units
Nautical Mile (UK) (NM (UK))
The UK nautical mile was historically defined as 6,080 feet, slightly longer than the international nautical mile (1,852 meters). Before international standardization in 1929, British charts and maritime documents relied on this definition. It approximated one minute of latitude but used British feet rather than an exact metric conversion. Although the UK adopted the international nautical mile long ago, many older navigation charts, historical records, and maritime traditions still reference the UK version. Researchers dealing with archival naval documents must carefully distinguish between the two definitions to avoid errors in distance or speed calculations. The UK nautical mile is a reminder of the era before global standardization when each nation maintained its own measurement conventions—even for activities as universally critical as seafaring.
Chain (US Survey) (ch (US))
The US Survey Chain is defined as 66 US Survey Feet (~20.1168 meters), aligning with the historic Gunter's chain but adapted to the US survey foot. It is used primarily in cadastral surveys, property delineation, and historical land records. Surveyors employ the chain for practical measurements of fields, lots, and infrastructure layouts. The unit's subdivision into 100 links simplifies area calculation, as 10 square chains equal one acre, maintaining continuity with older surveying systems. Even today, engineers and surveyors working with legacy data encounter the US survey chain in historical deeds, maps, and legal descriptions. Its precision ensures consistency when reconciling pre-modern measurements with modern coordinates.