US Survey Feet (ft-us) to furlongs (fur) conversion

What is the us survey foot?

What is US Survey Feet?

US Survey Feet is a unit of length used in the United States for land surveying. It is slightly different from the international foot. Understanding its origin and applications is crucial for accurate land measurements and legal descriptions.

Origin and Definition

The US Survey Foot (ftUS) is defined based on the Mendenhall Order of 1893, which related customary units to the metric system using the meter. At that time, it was defined as:

1 US Survey Foot = $\frac{3937}{1200}$ meters

This value equates to approximately 0.3048006096 meters. This differs slightly from the international foot which is exactly 0.3048 meters. The difference, while seemingly small (2 parts per million), can accumulate significantly over large distances, impacting land boundaries and area calculations.

The Issue & Readjustment

The difference between the international foot and the US survey foot caused discrepancies, especially in states that relied heavily on the Public Land Survey System (PLSS). Over time, states have addressed this issue in various ways:

• Many states have officially adopted the international foot for all new surveys.
• Some states continue to use the US Survey Foot. It's crucial to know which definition is in use for any particular survey or land description.
• Conversion factors are often provided in legal documents to clarify which foot is being used.

For more information about each state's definitions of feet, please read NOAA's definition of US Survey foot.

Usage and Real-World Examples

While its use is declining, the US Survey Foot is still relevant in some contexts, especially when dealing with older surveys and legal descriptions. Understanding its magnitude helps grasp spatial relationships:

• Property Boundaries: In states where it is still used, a land description stating a lot is 100 US Survey Feet wide means it is approximately 30.48006096 meters wide.
• Land Area Calculations: Area calculations, like acres, derived from measurements in US Survey Feet will differ slightly from those derived from international feet.
• Geographic Information Systems (GIS): GIS databases may contain data referenced to US Survey Feet, requiring proper transformation when integrating with data using the international foot.

Interesting Facts

• The slight difference between the two definitions of a foot has caused legal disputes related to property boundaries.
• The National Geodetic Survey (NGS) provides tools and resources for converting between the US Survey Foot and the international foot.

What is the furlong?

The furlong (fur) is a unit of length in the imperial and US customary systems, equal to one-eighth of a mile, most commonly used today in horse racing.

Definition

One furlong equals 660 feet, or 220 yards, or 40 rods, or 10 chains.

$$1\ \text{fur} = 201.168\ \text{m}$$

Eight furlongs make one statute mile. This value uses the international foot; the US survey furlong is larger by a factor of 1200/1199.

Origin and History

The name comes from Old English "furh" (furrow) and "lang" (long), meaning the length of a furrow in a ploughed open field. In the medieval English system, a furlong was the distance a team of oxen could plough before resting, standardized as the long side of a one-acre strip (one furlong by one chain). It became a fundamental unit of the English land-measurement system.

Law and Notable Facts

The furlong survives chiefly in horse racing, where race distances are quoted in furlongs (for example, a "six-furlong sprint"). It is also preserved in the definition of the acre and the mile. The whimsical furlong–firkin–fortnight (FFF) system uses it as an example of an intentionally impractical unit of length.

Real-World Examples and Conversions

• 1 furlong = 220 yd = 660 ft = 201.168 m.
• 8 furlongs = 1 statute mile.
• 1 furlong = 10 chains = 40 rods.
• The Kentucky Derby is run over 10 furlongs (1.25 miles).