<s>
The	O
correspondence	B-Algorithm
problem	I-Algorithm
refers	O
to	O
the	O
problem	O
of	O
ascertaining	O
which	O
parts	O
of	O
one	O
image	O
correspond	O
to	O
which	O
parts	O
of	O
another	O
image	O
,	O
where	O
differences	O
are	O
due	O
to	O
movement	O
of	O
the	O
camera	O
,	O
the	O
elapse	O
of	O
time	O
,	O
and/or	O
movement	O
of	O
objects	O
in	O
the	O
photos	O
.	O
</s>
<s>
Correspondence	O
is	O
a	O
fundamental	O
problem	O
in	O
computer	B-Application
vision	I-Application
—	O
influential	O
computer	B-Application
vision	I-Application
researcher	O
Takeo	O
Kanade	O
famously	O
once	O
said	O
that	O
the	O
three	O
fundamental	O
problems	O
of	O
computer	B-Application
vision	I-Application
are	O
:	O
“	O
Correspondence	O
,	O
correspondence	O
,	O
and	O
correspondence	O
!	O
”	O
Indeed	O
,	O
correspondence	O
is	O
arguably	O
the	O
key	O
building	O
block	O
in	O
many	O
related	O
applications	O
:	O
optical	O
flow	O
(	O
in	O
which	O
the	O
two	O
images	O
are	O
subsequent	O
in	O
time	O
)	O
,	O
dense	O
stereo	B-Algorithm
vision	I-Algorithm
(	O
in	O
which	O
two	O
images	O
are	O
from	O
a	O
stereo	O
camera	O
pair	O
)	O
,	O
structure	B-Algorithm
from	I-Algorithm
motion	I-Algorithm
(	O
SfM	O
)	O
and	O
visual	O
SLAM	B-Application
(	O
in	O
which	O
images	O
are	O
from	O
different	O
but	O
partially	O
overlapping	O
views	O
of	O
a	O
scene	O
)	O
,	O
and	O
cross-scene	B-Algorithm
correspondence	I-Algorithm
(	O
in	O
which	O
images	O
are	O
from	O
different	O
scenes	O
entirely	O
)	O
.	O
</s>
<s>
Given	O
two	O
or	O
more	O
images	O
of	O
the	O
same	O
3D	O
scene	O
,	O
taken	O
from	O
different	O
points	O
of	O
view	O
,	O
the	O
correspondence	B-Algorithm
problem	I-Algorithm
refers	O
to	O
the	O
task	O
of	O
finding	O
a	O
set	O
of	O
points	O
in	O
one	O
image	O
which	O
can	O
be	O
identified	O
as	O
the	O
same	O
points	O
in	O
another	O
image	O
.	O
</s>
<s>
To	O
do	O
this	O
,	O
points	O
or	O
features	B-Algorithm
in	O
one	O
image	O
are	O
matched	O
with	O
the	O
points	O
or	O
features	B-Algorithm
in	O
another	O
image	O
,	O
thus	O
establishing	O
corresponding	B-Algorithm
points	I-Algorithm
or	O
corresponding	B-Algorithm
features	I-Algorithm
,	O
also	O
known	O
as	O
homologous	B-Algorithm
points	I-Algorithm
or	O
homologous	O
features	B-Algorithm
.	O
</s>
<s>
The	O
correspondence	B-Algorithm
problem	I-Algorithm
can	O
occur	O
in	O
a	O
stereo	O
situation	O
when	O
two	O
images	O
of	O
the	O
same	O
scene	O
are	O
used	O
,	O
or	O
can	O
be	O
generalised	O
to	O
the	O
N-view	O
correspondence	B-Algorithm
problem	I-Algorithm
.	O
</s>
<s>
A	O
typical	O
application	O
of	O
the	O
correspondence	B-Algorithm
problem	I-Algorithm
occurs	O
in	O
panorama	B-Application
creation	O
or	O
image	B-Algorithm
stitching	I-Algorithm
—	O
when	O
two	O
or	O
more	O
images	O
which	O
only	O
have	O
a	O
small	O
overlap	O
are	O
to	O
be	O
stitched	O
into	O
a	O
larger	O
composite	O
image	O
.	O
</s>
<s>
In	O
this	O
case	O
it	O
is	O
necessary	O
to	O
be	O
able	O
to	O
identify	O
a	O
set	O
of	O
corresponding	B-Algorithm
points	I-Algorithm
in	O
a	O
pair	O
of	O
images	O
in	O
order	O
to	O
calculate	O
the	O
transformation	O
of	O
one	O
image	O
to	O
stitch	O
it	O
onto	O
the	O
other	O
image	O
.	O
</s>
<s>
Feature-based	O
–	O
finding	O
features	B-Algorithm
in	O
the	O
image	O
and	O
seeing	O
if	O
the	O
layout	O
of	O
a	O
subset	O
of	O
features	B-Algorithm
is	O
similar	O
in	O
the	O
two	O
images	O
.	O
</s>
<s>
In	O
computer	B-Application
vision	I-Application
the	O
correspondence	B-Algorithm
problem	I-Algorithm
is	O
studied	O
for	O
the	O
case	O
when	O
a	O
computer	O
should	O
solve	O
it	O
automatically	O
with	O
only	O
images	O
as	O
input	O
.	O
</s>
<s>
Once	O
the	O
correspondence	B-Algorithm
problem	I-Algorithm
has	O
been	O
solved	O
,	O
resulting	O
in	O
a	O
set	O
of	O
image	O
points	O
which	O
are	O
in	O
correspondence	O
,	O
other	O
methods	O
can	O
be	O
applied	O
to	O
this	O
set	O
to	O
reconstruct	B-Algorithm
the	O
position	O
,	O
motion	O
and/or	O
rotation	O
of	O
the	O
corresponding	O
3D	O
points	O
in	O
the	O
scene	O
.	O
</s>
<s>
The	O
correspondence	B-Algorithm
problem	I-Algorithm
is	O
also	O
the	O
basis	O
of	O
the	O
particle	O
image	O
velocimetry	O
measurement	O
technique	O
,	O
which	O
is	O
nowadays	O
widely	O
used	O
in	O
the	O
fluid	O
mechanics	O
field	O
to	O
quantitatively	O
measure	O
fluid	O
motion	O
.	O
</s>
<s>
A	O
simple	O
method	O
is	O
to	O
compare	O
small	O
patches	O
between	O
rectified	B-Algorithm
images	I-Algorithm
.	O
</s>
