Transcript Vegetation Indices and LAI

SKYE INSTRUMENTS LTD
Llandrindod Wells, United Kingdom
SPECTROSENSE2+
1. SpectroSense2+ Meter
2. Spectral Reflectance
3. Vegetation Indices
4. SpectroSense2+ Configurations
SPECTROSENSE2+
1. SpectroSense2+ Meter
2. Spectral Reflectance
3. Vegetation Indices
4. SpectroSense2+ Configurations
SPECTROSENSE2+
SPECTROSENSE 2+.GPS
• 8 channel meter
• Display 8 readings at
once
• Ratio of incident /
reflected
• Store function
• Automatic datalogging
• VI & LAI calculations
• GPS for field mapping
SPECTROSENSE2+
VEGETATION INDICES (VIs)
• “Greenness” Index
• Detects presence of vegetation
• Measures ratios of spectral
bands
• Estimate plant biomass / cover
• Identify plant species
• Detect plant health / disease
SPECTROSENSE2+
VEGETATION INDICES (VIs)
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Applications
Crops & Horticulture,
Precision Agriculture
Climate Change
Satellite Ground
Truthing
Carbon Balance
SPECTROSENSE2+
VI Calculations
• NDVI & PRI
• MODIS EVI
• EVI2 & MSAVI2
• RVI & WBI
• LAI
• fPAR
• Individual readings
SPECTROSENSE2+
1. SpectroSense2+ Meter
2. Spectral Reflectance
3. Vegetation Indices
4. SpectroSense2+ Configurations
SPECTROSENSE2+
SPECTRAL REMOTE SENSING
Measuring Reflected
Light
• Different surfaces reflect
different wavelengths
• Easy identification of land,
ocean, forest, desert etc
• Satellite maps
• Ground truth maps
SPECTROSENSE2+
SPECTRAL REMOTE SENSING
Measuring Reflected Light
• VIS, NIR and SWIR
wavelengths
• Each surface has a
“fingerprint” spectrum
• Low values - absorption
• High values - reflectance
SPECTROSENSE2+
SPECTROSENSE2+
SPECTROSENSE2+
SPECTROSENSE2+
SPECTROSENSE2+
VEGETATION INDICES (VIs)
• Calculated from reflected
radiation
• “Greenness” Indices
• Detects presence of vegetation
• Estimate plant biomass / cover
• Identify plant species
• Detect plant health / disease
SPECTROSENSE2+
1. SpectroSense2+ Meter
2. Spectral Reflectance
3. Vegetation Indices
4. SpectroSense2+ Configurations
SPECTROSENSE2+
SIMPLE RATIO VEGETATION INDICES
Simple Ratio of two Wavelengths
RVI Relative Vegetation Index
Uses Red and NIR bands
WBI Water Band Index
Uses 970nm and 990 nm bands
SPECTROSENSE2+
Relative Vegetation Index
RVI =
NIR
Red
SPECTROSENSE2+
RVI
Ranges from 0 to infinity
0
>0
bare soil
vegetation
SPECTROSENSE2+
Water Band Index
WBI = R900 or R900
R970
R1530
Surface wetness, water vapour flux
SPECTROSENSE2+
WBI
For Green Vegetation
Range is 0.8 to 1.2
SPECTROSENSE2+
NDVI
Normalised Differential Vegetation
Index
• The most widely used “greenness” VI
• Measure ratios of NIR to Red
• Estimates amount of Biomass & Ground
Cover
• Health Status of plants
SPECTROSENSE2+
Normalised Differential Vegetation
Index
NDVI
=
(RNIR - RRed)
(RNIR + RRed)
This has limitations in dense
vegetation
SPECTROSENSE2+
NDVI
Ranges from
-1
0
+1
ice and snow
bare soil
full vegetation cover
SPECTROSENSE2+
Fraction of PAR
Absorbed by the plant canopy
fPAR = 1.24 * NDVI - 0.168
Strongly linked to LAI Leaf Area
Index
SPECTROSENSE2+
fPAR
Ranges from
-1
0
+1
ice and snow
bare soil
full vegetation cover
SPECTROSENSE2+
LAI Leaf Area Index
LAI = Total upper leaf surface
Ground surface area
0 = bare soil
6 = dense forest
Can be estimated using NDVI
SPECTROSENSE2+
LAI Leaf Area Index
From NDVI
LAI
= a * e (b * NDVI)
where a = 0.0148, e = exponential, b = 6.192
SPECTROSENSE2+
PRI
Photochemical Reflective
Index
• Measure ratios of Green to
Yellow
• Rate of photosynthesis
• Light Use Efficiency LUE
• Health Status of plants
• Productivity of plants
SPECTROSENSE2+
PRI = Photochemical Reflective Index
PRI =
(R570 - R531)
(R570 + R531)
corresponds with Xanthophyll Cycle activity
& LUE Light Use Efficiency
SPECTROSENSE2+
PRI
Ranges from
-1 to +1
Healthy Vegetation
-0.2 to +0.2
SPECTROSENSE2+
MODIS EVI
Enhanced Vegetation Index
• Uses MODIS bands 1, 2 and 3
• Red, NIR and Blue
• Better sensitivity for high
biomass
• Responsive to canopy structure
SPECTROSENSE2+
MODIS EVI
EVI =
G
(RNIR - RRed)
*
(RNIR+ C1*RRed - C2*RBlue + L )
where C1=6, C2=7.5, L=1, G=2.5
SPECTROSENSE2+
MODIS EVI
Ranges from
-1 to +1
Healthy Vegetation
0.2 to 0.8
SPECTROSENSE2+
EVI2
2 band Enhanced Vegetation
Index
• Uses just Red and NIR bands
• Blue band not required
• Good correlation with MODIS EVI
SPECTROSENSE2+
EVI2
EVI2 =
2.5 * (RNIR - RRed)
(RNIR + 2.4 * RRed + 1)
2 band Enhanced Vegetation Index
SPECTROSENSE2+
EVI2
Ranges from
-1 to +1
Healthy Vegetation
0.2 to 0.8
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MSAVI2
Modified Soil Adjusted Vegetation
Index
• Uses Red and NIR bands
• Compensates for exposed soil areas
• Best where vegetation cover is <40%
SPECTROSENSE2+
MSAVI2
MSAVI2 = (2*RNIR+ 1) - [(2 * RNIR+ 1)2 - 8*(RNIR RRed)]
2
Modified Soil Adjusted Vegetation Index
SPECTROSENSE2+
MSAVI2
Ranges from
-1
0
+1
ice and snow
bare soil
full vegetation cover
SPECTROSENSE2+
LAI Leaf Area Index
LAI = Total upper leaf surface
Ground surface area
0 = bare soil
6 = dense forest
Can be estimated using PAR Sensors
SPECTROSENSE2+
LAI Leaf Area Index
Using a pair of PAR Sensors
An Incident PAR sensor above the canopy
A Line PAR sensor below the canopy
LAI
= -2 * ln (PARLQ / PARI)
SPECTROSENSE2+
1. SpectroSense2+ Meter
2. Spectral Reflectance
3. Vegetation Indices
4. SpectroSense2+ Configurations
SPECTROSENSE2+
SPECTROSENSE 2+.GPS
• One SpectoSense2+
meter
• Two identical sensors
• GPS module for mapping
• Hand held pole
• Carry case
SPECTROSENSE2+
TWO IDENTICAL SENSORS
• Cosine corrected for
incident light
measurements
• Narrow angle FOV sensor
for reflected light
measurements
• Simultaneous readings
allow use in any light
conditions
SPECTROSENSE2+
Sensor 1
Sensor 2
25°
h
r
TWO OR FOUR BAND
SENSORS
• Specially designed geometry
of narrow angle light
acceptance
• Changing the height above
the ground changes the area
of measurement
• E.g. 1.8m height = 0.5m2
area
SPECTROSENSE2+
HAND HELD NDVI SYSTEM
• SpectroSense2+ meter
• Two 2 channel sensors
• Red and NIR bands
• NDVI & RVI
• fPAR & LAI
• EVI2 & MSAVI
SPECTROSENSE2+
MODIS EVI SYSTEM
• SpectoSense2+ meter
• Two 3 or 4 channel
sensors
• Blue, Red and NIR
bands
• NDVI & RVI
• fPAR & LAI
• MODIS EVI
• EVI2 & MSAVI
SPECTROSENSE2+
NDVI / PRI SYSTEM
• SpectroSense2+ meter
• Two 4 channel sensors
• Red, NIR, 531 & 570nm
bands
• NDVI & RVI
• fPAR & LAI
• EVI2 & MSAVI
• PRI
SPECTROSENSE2+
LEAF AREA INDEX
• Two PAR sensors
• Incident PAR sensor
above canopy
• Line PAR sensor
below canopy
SKYE INSTRUMENTS LTD
Llandrindod Wells, United Kingdom