Vegetation Indices VIs

1
Vegetation Indices(VIs)
2
Monitoring usingVIs

• Basis

3
(No Transcript)
4
Why VIs?

• empirical relationships with range of vegetation
  / climatological parameters
• fAPAR
• NPP
• simple (understand/implement)
• fast (ratio, difference etc.)

5
Why VIs?

• tracking of temporal characteristics /
  seasonality
• can reduce sensitivity to
• topographic effects
• (soil background)
• (view/sun angle (?))
• (atmosphere)
• whilst maintaining sensitivity to vegetation

6
(No Transcript)
7
(No Transcript)
8
Some VIs

• RVI (ratio)
• DVI (difference)
• NDVI

9
why NDVI?

• continuity (17 years of AVHRR NDVI)

10
limitations of NDVI

• atmospheric effects
• esp. aerosols (turbid - decrease)
• direct means - atmospheric correction
• indirect means atmos.-resistant VI (ARVI/GEMI)
• sun-target-sensor effects (BRDF)
• MVC ? - ok on cloud, not so effective on BRDF
• saturation problems
• saturates at VI of 2-3

11
limitations of NDVI

• non-linear relationships to fAPAR, LAI
• saturation / more complex (?) model
• use RVI?
• background effects
• soil line concept
• canopy structural effects (LAD)
• empirical relationships site/crop specific
• relationship with cover type?
• residual topographic effects
• DEM correction?

12
(No Transcript)
13
(No Transcript)
14
New indices

• WDVI (Clevers, 1989)
• k - RVI of background

15
New indices

• SAVI (Huete, 1988)
• L - soil adjustment factor

16
New indices

• PVI (Richardson and Wiegand, 1977)
• a - soil line slope, b - soil line intercept

17
New indices

• GEMI (Pinty and Verstraete, 1992)

18
New indices

• Green NDVI
• better satn. properties than using red (?)

19
New indices

• SARVI (Huete, 1996)
• L - background term as before
• C1,2 - weights blue in aerosol correction
• designed for use on MODIS

20
(No Transcript)
21
(No Transcript)
22
(No Transcript)
23
(No Transcript)
24
(No Transcript)
25
(No Transcript)
26
(No Transcript)
27
(No Transcript)
28
(No Transcript)