<s>
A	O
vegetation	B-General_Concept
index	I-General_Concept
(	O
VI	O
)	O
is	O
a	O
spectral	O
imaging	O
transformation	O
of	O
two	O
or	O
more	O
image	O
bands	O
designed	O
to	O
enhance	O
the	O
contribution	O
of	O
vegetation	O
properties	O
and	O
allow	O
reliable	O
spatial	O
and	O
temporal	O
inter-comparisons	O
of	O
terrestrial	O
photosynthetic	O
activity	O
and	O
canopy	O
structural	O
variations	O
.	O
</s>
<s>
Since	O
the	O
1960s	O
scientists	O
have	O
used	O
satellite	O
remote	B-Application
sensing	I-Application
to	O
monitor	O
fluctuation	O
in	O
vegetation	O
at	O
the	O
Earth	O
's	O
surface	O
.	O
</s>
<s>
Due	O
to	O
advances	O
in	O
hyperspectral	O
remote	B-Application
sensing	I-Application
technology	I-Application
,	O
high-resolution	O
reflectance	O
spectrums	O
are	O
now	O
available	O
,	O
which	O
can	O
be	O
used	O
with	O
traditional	O
multispectral	O
VIs	O
.	O
</s>
<s>
In	O
addition	O
,	O
VIs	O
have	O
been	O
developed	O
to	O
be	O
used	O
specifically	O
with	O
hyperspectral	O
data	O
,	O
such	O
as	O
the	O
use	O
of	O
Narrow	O
Band	O
Vegetation	B-General_Concept
Indices	I-General_Concept
.	O
</s>
<s>
Vegetation	B-General_Concept
indices	I-General_Concept
have	O
been	O
used	O
to	O
:	O
</s>
<s>
Normalised	O
Difference	O
Vegetation	B-General_Concept
Index	I-General_Concept
(	O
NDVI	O
)	O
:	O
The	O
most	O
commonly	O
used	O
remote	B-Application
sensing	I-Application
index	O
that	O
calculates	O
the	O
ratio	O
of	O
the	O
difference	O
and	O
sum	O
between	O
the	O
Near	O
Infrared	O
and	O
Red	O
bands	O
of	O
multispectral	O
images	O
.	O
</s>
<s>
Enhanced	O
Vegetation	B-General_Concept
Index	I-General_Concept
(	O
EVI	O
)	O
:	O
Very	O
similar	O
to	O
NDVI	O
.	O
</s>
<s>
With	O
the	O
advent	O
of	O
hyperspectral	O
data	O
,	O
vegetation	B-General_Concept
index	I-General_Concept
have	O
been	O
developed	O
specifically	O
for	O
hyperspectral	O
data	O
.	O
</s>
<s>
With	O
the	O
emergence	O
of	O
machine	O
learning	O
,	O
certain	O
algorithms	O
can	O
be	O
used	O
to	O
determine	O
vegetation	B-General_Concept
indices	I-General_Concept
from	O
data	O
.	O
</s>
<s>
This	O
allows	O
to	O
take	O
into	O
account	O
all	O
spectral	O
bands	O
and	O
to	O
discover	O
hidden	O
parameters	O
that	O
can	O
be	O
useful	O
to	O
strengthen	O
these	O
vegetation	B-General_Concept
indices	I-General_Concept
.	O
</s>
