US Survey Feet (ft-us) to rods (rd) 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 rod?

The rod (rd) is a unit of length in the imperial and US customary systems, equal to 16.5 feet, historically used in surveying and land measurement. It is also called the pole or perch.

Definition

One rod equals 16.5 feet, or 5.5 yards, or one-quarter of a chain.

$$1\ \text{rd} = 5.02920\ \text{m}$$

There are 4 rods in a chain, 40 rods in a furlong, and 320 rods in a mile. This value uses the international foot; the US survey rod is larger by a factor of 1200/1199.

Origin and History

The rod derives from medieval European land-measurement practice, where an actual wooden rod or pole was used to lay out fields. One traditional definition took the rod as the combined length of the left feet of 16 men lined up as they left church on a Sunday morning, averaging out individual variation. The value of 16.5 feet was standardized in England and carried into colonial America.

Law and Notable Facts

The rod, also known as the pole or perch, remains embedded in old deeds and the US Public Land Survey System. The square rod (or square perch) was a common area unit for gardens and small plots. The rod is essentially obsolete today except in legal descriptions of land and some fencing and forestry contexts.

Real-World Examples and Conversions

• 1 rod = 16.5 ft = 5.5 yd = 5.0292 m.
• 4 rods = 1 chain; 40 rods = 1 furlong; 320 rods = 1 mile.
• An acre is 160 square rods.
• A standard rod is a bit longer than a typical car (about 5 m).