Physical unit
Unit symbol ${\ displaystyle {\ mathsf {fm}}}$
Physical quantity (s) length
Formula symbol ${\ displaystyle l}$
dimension ${\ displaystyle {\ mathsf {L}}}$
system Anglo-American system of measurement
In SI units ${\ displaystyle \ mathrm {1 \, fm = 1 {,} 828 \, 8 \; m}}$
Derived from yard

The board thread (from the English "fathom", to German: "thread", and " fathom called") is a non- SI -compliant unit of length which especially in the English-language navigation - in the nautical - for depth indications in use is. Originally, the measure was the span of the arms of a full-grown man, historically equated to six feet, the fathom.

1 sc = 2 yd = 6 ft = 72 in = 182.88 cm = 1.8288 m
1 statute mile = 880 fm

Occasionally a newer, non-standardized definition is used:

1 fm = 1/100 cable length = 1/1000 nautical mile = 1.852 m

In the EC Directive 80/181 / EEC, the first definition is based on, but rounded the numerical value to 1,829 meters.

## Different definition of thread in seafaring

The Paris line is calculated here with 2.2558 mm.

designation int. Paris lines meter
Prussian thread 1 thread = 6 feet (Prussian) = 1/2 rod 736.2 1.88312 meters
Danish thread 1 favo = 6 feet 834.7 1.88291626
French thread 1 bream = 5 feet 720 1.624176
Hamburger thread 1 HF = 6 feet 762 1.7189196
Dutch thread 1 Vaam = 6 feet 834.8 1.88314184
Neapolitan thread 1 NF = 5 feet 720 1.624176
Portuguese thread 1 Braca = 8 palmos 775.2 1.74869616
Swedish thread 1 SF = 6 feet 789.6 1.781968

(Sources below)