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Part of international standard ISO 31
ISO 31-1
[1]
is the part of
international standard
ISO 31
that defines names and symbols for
quantities
and
units
related to
space
and
time
. It was superseded in 2006 by
ISO 80000-3
.
Definitions
[
edit
]
Its definitions include:
Quantity
|
Unit
|
Remarks
|
Name
|
Symbol
|
Name
|
Symbol
|
Definition
|
angle
,
(plane angle)
|
α, β, γ, θ, φ
|
radian
|
rad
|
1 rad = 1
m
⁄
m
= 1
|
|
degree
|
°
|
1° =
π
⁄
180
rad
|
There is no space between the number and these superscript-style unit symbols. Decimal subdivision of degrees is preferable (i.e., 12.5° instead of 12°30′)
|
minute
|
′
|
1′ = (
1
⁄
60
)°
|
second
|
″
|
1″ = (
1
⁄
60
)′
|
solid angle
|
Ω
|
steradian
|
sr
|
1 sr = 1
m
2
⁄
m
2
= 1
|
|
length
|
l, L
|
metre
|
m
|
The metre is the length of the path travelled by light in vacuum during a time interval of
1
⁄
299 792 458
of a second; see
speed of light
|
|
breadth
|
b
|
height
|
h
|
thickness
|
d, δ
|
radius
|
r, R
|
diameter
|
d, D
|
length of path
,
(linear) displacement vector
|
s,
s
|
distance
|
d, r
|
cartesian coordinates
|
x, y, z
|
radius of curvature
|
?
|
curvature
|
?
|
reciprocal metre
|
m
?1
|
|
|
area
|
A
|
square metre
|
m
2
|
|
The units
are
(1 a = 100 m
2
) and
hectare
(1 ha = 100 a) are used for agrarian areas.
|
volume
|
V
|
cubic metre
|
m
3
|
|
|
litre
|
L, l
|
1 L = 1 dm
3
|
The capital L is preferred as the small l can be indistinguishable from the number 1 in some fonts.
|
time
,
time interval
,
duration
|
t
|
second
|
s
|
The second is the duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two
hyperfine levels
of the
ground state
of the
caesium
-133 atom
|
Representations of time of day are defined in
ISO 8601
.
|
minute
|
min
|
1 min = 60 s
|
hour
|
h
|
1 h = 60 min = 3 600 s
|
day
|
d
|
1 d = 24 h = 1 440 min = 86 400 s
|
angular velocity
|
ω
|
radian per second
|
rad
⁄
s
|
|
ω=
dφ
⁄
dt
|
angular acceleration
|
α
|
radian per second squared
|
rad
⁄
s
2
|
|
α=
dω
⁄
dt
|
velocity
|
v
(general symbol),
v
(velocity vector),
c
(propagation speed of waves),
u
,
v
,
w
(components of a velocity
c
)
|
metre per second
|
m
⁄
s
|
|
|
kilometre per hour
|
km
⁄
h
|
|
|
acceleration
, acceleration vector
|
a,
a
|
metre per second squared
|
m
⁄
s
2
|
1
g
= 9.80665
m
⁄
s
2
|
|
acceleration of free fall
,
acceleration due to gravity
|
g
|
Annex A
[
edit
]
Annex A of ISO 31-1 lists units of space and time based on the
foot
,
pound
, and
second
.
Annex B
[
edit
]
Annex B lists some other non-SI units of space and time, namely the
gon
,
light year
,
astronomical unit
,
parsec
,
tropical year
, and
gal
.
References
[
edit
]
ISO
standards
by standard number
|
---|
|
1?9999
| |
---|
10000?19999
| |
---|
20000?29999
| |
---|
30000+
| |
---|
|