<s>
In	O
the	O
field	O
of	O
computer	B-Application
vision	I-Application
,	O
velocity	B-General_Concept
moments	I-General_Concept
are	O
weighted	O
averages	O
of	O
the	O
intensities	O
of	O
pixels	O
in	O
a	O
sequence	O
of	O
images	O
,	O
similar	O
to	O
image	B-Algorithm
moments	I-Algorithm
but	O
in	O
addition	O
to	O
describing	O
an	O
object	O
's	O
shape	O
also	O
describe	O
its	O
motion	O
through	O
the	O
sequence	O
of	O
images	O
.	O
</s>
<s>
Velocity	B-General_Concept
moments	I-General_Concept
can	O
be	O
used	O
to	O
aid	O
automated	O
identification	O
of	O
a	O
shape	O
in	O
an	O
image	O
when	O
information	O
about	O
the	O
motion	O
is	O
significant	O
in	O
its	O
description	O
.	O
</s>
<s>
There	O
are	O
currently	O
two	O
established	O
versions	O
of	O
velocity	B-General_Concept
moments	I-General_Concept
:	O
Cartesian	O
and	O
Zernike	O
.	O
</s>
<s>
Cartesian	O
velocity	B-General_Concept
moments	I-General_Concept
are	O
based	O
on	O
these	O
Cartesian	O
moments	O
.	O
</s>
<s>
As	O
Cartesian	O
moments	O
are	O
non-orthogonal	O
,	O
so	O
are	O
Cartesian	O
velocity	B-General_Concept
moments	I-General_Concept
,	O
so	O
different	O
moments	O
can	O
be	O
closely	O
correlated	O
.	O
</s>
<s>
These	O
velocity	B-General_Concept
moments	I-General_Concept
do	O
however	O
provide	O
translation	O
and	O
scale	O
invariance	O
(	O
unless	O
the	O
scale	O
changes	O
within	O
the	O
sequence	O
of	O
images	O
)	O
.	O
</s>
<s>
Zernike	O
velocity	B-General_Concept
moments	I-General_Concept
are	O
based	O
on	O
these	O
Zernike	O
moments	O
.	O
</s>
<s>
introduces	O
velocity	O
into	O
the	O
equation	O
in	O
the	O
same	O
way	O
as	O
in	O
the	O
Cartesian	O
velocity	B-General_Concept
moments	I-General_Concept
and	O
is	O
from	O
the	O
Zernike	O
moments	O
equation	O
above	O
.	O
</s>
<s>
As	O
Zernike	O
velocity	B-General_Concept
moments	I-General_Concept
are	O
based	O
on	O
the	O
orthogonal	O
Zernike	O
moments	O
,	O
they	O
produce	O
less	O
correlated	O
and	O
more	O
compact	O
descriptions	O
than	O
Cartesian	O
velocity	B-General_Concept
moments	I-General_Concept
.	O
</s>
<s>
Zernike	O
velocity	B-General_Concept
moments	I-General_Concept
also	O
provide	O
translation	O
and	O
scale	O
invariance	O
(	O
even	O
when	O
the	O
scale	O
changes	O
within	O
the	O
sequence	O
)	O
.	O
</s>
