ft-us to fathom | Convert US Survey Foot to Fathom

US Survey Foot to Fathom Conversion Formula Example What is a US Survey Foot (ft-us)?Where Did the US Survey Foot Come From?Why Was the US Survey Foot Replaced?Why Did This Small Difference Cause Big Problems?What is a Fathom, and How Long Is It?Fathom at a Glance:Where Does the Word 'Fathom' Come From?How Was the Fathom Used at Sea?Is the Fathom Still Used Today?What is the imperial system?US Survey Foot to Fathom Conversion Table

US Survey Foot to Fathom Conversion Formula

To convert from US Survey Foot (ft-us) to Fathom (fathom), use the following formula:

$\textbf{ Fathom} \text{ (fathom)}$

$= 1.000002 \times \frac{1}{6}\times \textbf{ US Survey Foot} \text{ (ft-us)}$

$= 0.166667\times \textbf{ US Survey Foot} \text{ (ft-us)}$

Example

Let's convert 5 US Survey Foot (ft-us) to Fathom (fathom).

Using the formula:

$5 \times 0.166667 = 0.833335$

Therefore, 5 US Survey Foot (ft-us) is equal to $0.833335$ Fathom (fathom).

What is a US Survey Foot (ft-us)?

The US Survey Foot is a unit of length historically used for land surveying in the United States.

It is very close in length to the international foot, equaling approximately 1.000002 international feet (ft). The plural form is US Survey Feet.

Where Did the US Survey Foot Come From?

The origin of the US Survey Foot dates back to the Mendenhall Order of 1893. This order defined the relationship between the meter and US customary units.

It established that 1 meter is precisely equal to 39.37 inches. From this relationship, the US Survey Foot was derived, defined as 1200/3937 meters.

This definition differs slightly from the international foot, which was established in 1959 and is defined as exactly 0.3048 meters.

Why Was the US Survey Foot Replaced?

To simplify measurements and prevent confusion, the National Institute of Standards and Technology (NIST) and the National Geodetic Survey (NGS) made a critical change.

They officially retired the U.S. Survey Foot on December 31, 2022.

Surveying and mapping applications in the United States will now use the international foot. This critical change helps unify the National Spatial Reference System (NSRS) and prevents costly errors in large-scale projects.

Why Did This Small Difference Cause Big Problems?

While the difference between a US Survey Foot and an international foot is minuscule—only about two parts per million—it becomes significant over large distances.

For every mile, the discrepancy adds up to approximately 1/8 inch.

This minor error may not be significant for a backyard fence. However, for massive construction projects and infrastructure development, such as bridges that cross state lines, the accumulated error can lead to severe misalignments and costly mistakes.

What is a Fathom, and How Long Is It?

A fathom is a unit of length in the imperial system of measurement.

It is most famously used for measuring the depth of water.

A fathom is equal to exactly 6 feet (or 1.8288 meters). The plural form is fathoms.

Fathom at a Glance:

Unit of: Length
System: Imperial & U.S. Customary
Equal to: 6 feet (1.8288 meters)

Where Does the Word 'Fathom' Come From?

The word "fathom" originates from the Old English word "fæthm," which means "outstretched arms" or "a pair of embracing arms."

Historically, a fathom was defined as the distance from the middle fingertip of one hand to the middle fingertip of the other when a person's arms are fully extended.

This made it a convenient and readily available unit of measurement for sailors and workers.

How Was the Fathom Used at Sea?

The fathom is best known for its use in a nautical context to measure water depth.

Mariners would drop a weighted line, called a sounding line, into the water and count the number of "arm spans" it took to reach the bottom.

This measurement was crucial for safe navigation, anchoring, and creating nautical charts to map the seabed.

Is the Fathom Still Used Today?

While modern technology and the metric system have replaced the fathom in official hydrographic surveys, its influence persists.

The term is still used informally in commercial fishing and can be found on many older nautical charts.

Figuratively, the verb "to fathom"—meaning to understand something deeply—is a direct link to the original act of measuring depth and getting to the bottom of things.

What is the imperial system?

The imperial system is a system of measurement that was first defined in the British Weights and Measures Act of 1824. It's known for using units like inches, feet, pounds, and gallons. While most of the world now uses the metric system, the imperial system remains the official system of measurement in the United States and is still used in specific contexts in other countries, such as the United Kingdom and Canada.

US Survey Foot to Fathom Conversion Table

Here are some quick reference conversions from US Survey Foot (ft-us) to Fathom (fathom):

US Survey Feet	Fathoms
0.000001 ft-us	$1.66667\times 10^{-7}$ fathom
0.001 ft-us	$0.000166667$ fathom
0.1 ft-us	$0.0166667$ fathom
1 ft-us	$0.166667$ fathom
2 ft-us	$0.333334$ fathom
3 ft-us	$0.500001$ fathom
4 ft-us	$0.666668$ fathom
5 ft-us	$0.833335$ fathom
6 ft-us	$1.000002$ fathom
7 ft-us	$1.166669$ fathom
8 ft-us	$1.333336$ fathom
9 ft-us	$1.500003$ fathom
10 ft-us	$1.66667$ fathom
20 ft-us	$3.33334$ fathom
30 ft-us	$5.00001$ fathom
40 ft-us	$6.66668$ fathom
50 ft-us	$8.33335$ fathom
100 ft-us	$16.6667$ fathom
1000 ft-us	$166.667$ fathom
10000 ft-us	$1666.67$ fathom

Convert Length from Us Survey Foot to Fathom (ft-us to fathom)

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