SME
Remote Sensing · Problem type
NDVI of a pixel
Use this for “A pixel reflects 0.45 of near-infrared light and 0.08 of red light. What is its NDVI?”
Diagram
NDVI
=
NIR − red
NIR + red
=
0.45 − 0.08
0.45 + 0.08
=
0.698.
The curves are typical shapes, drawn for reference.
This is an example. Type your own values to start a new problem.
NDVI
=
(
NIR
−
Red
)
÷
(
NIR
+
Red
)
Formulas
NDVI
=
NIR − Red
NIR + Red
0.6981
=
0.45 − 0.08
0.45 + 0.08
Assumptions
•
NDVI = (NIR − Red) ÷ (NIR + Red), both as reflectances from 0 to 1, so NDVI runs from −1 to 1.
•
Healthy leaves reflect near infrared strongly and absorb red light, so dense green plants give high NDVI.
•
Water and bare soil give values near or below 0.2; clouds and snow give values near 0 or below.
Step-by-step
WE KNOW
NIR = 0.45, Red = 0.08
FIND
NDVI (NDVI)
Step 1 · Find NDVI (NDVI)
Use NDVI = (NIR − Red) ÷ (NIR + Red)
The gap between the bands over their sum, so brightness cancels and only the contrast is left.
NDVI
=
0.45 − 0.08
0.45 + 0.08
0.45 − 0.08 = 0.37
0.45 + 0.08 = 0.53
NDVI = 0.6981
Check
Put the numbers back in. Both sides should match.
0.6981
=
0.45 − 0.08
0.45 + 0.08
✓
Topic check
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