performance of intrinsic vegetation indices from …egypt - us workshop on space technology and...

Performance of Intrinsic Vegetation Indices from

EgyptSat-1 Satellite

Dr. Islam Abou El-Magd, CSci, CEnv

NARSS

Egypt - US Workshop on Space Technology and Geo-information for Sustainable Development,Cairo, Egypt 14-17 June, 2010

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Overview• Vegetation Indices

• EgyptSat1 Sensor Specs

• Common RS Sensors

• VIs Results

• Limitations

• Conclusion


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• It is developed to assess and monitor different land changes particularly for vegetation.

• It relies on the spectral properties of the vegetation cover at different stages of growth

• Vegetation indices vary from simple ratio (e.g. VI) to complicated and advanced index (e.g. TSAVI)

• Simplicity and complication is function of the spectral channels and the application

Indices (e.g. Vegetation Index)


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Vegetation Index


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EgyptSat-1 Specs

Mode Parameter Descriptions Panchromatic Spectral Resolution Band1 (0.5 – 0.89 µm) Spatial Resolution 7.8 × 7.8 Meter Swath Width 46 Km Multi-spectral Spectral Resolution Band1 (0.51 – 0.59 µm) Band2 (0.61 – 0.68 µm) Band3 (0.80 – 0.89 µm) Spatial Resolution 7.8 × 7.8 Meter Swath Width 46 Km Mid Infrared Band1 (1.1 – 1.7 µm) 38 × 38 Meter Swath Width 55 Km


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Spectral Comparison

Spectral band

EgyptSat-1 SPOT 4 DiscrepancyStart End

Landsat ETM

DiscrepancyStart End

Red 0.61 – 0.68 µm 0.61 - 0.68 - & - 0.63 – 0.69 -2 & +1

NIR 0.80 – 0.89 µm 0.78 – 0.89 +2 & - 0.78 – 0.90 -2 & -


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Pilot Area of StudyAgricultural land mixed with other categories of Land uses


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VI• VI measures

the level of photosynthetic activity in the vegetation cover within the image

RIRVI =


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VIR2 = 0.76

0

0.10.2

0.30.4

0.5

0.60.7

0.80.9

1

0 0.2 0.4 0.6 0.8 1

Landsat ETM

EgyptSat‐1

R2 = 0.72

0

0.10.2

0.3

0.40.5

0.6

0.7

0.80.9

1

0 0.2 0.4 0.6 0.8 1

SPOT 4

EgyptSat‐1


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NDVI• NDVI identifies the

photosynthetic affinity or greenness of the vegetation through the reflective properties of the chlorophyll layer within the plants in the NIR and Red spectrum

RIRRIRNDVI

+−

=


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NDVIR2 = 0.69

0

0.1

0.20.3

0.4

0.5

0.6

0.70.8

0.9

1

0 0.2 0.4 0.6 0.8 1

Landsat ETM

EgyptSat‐1

R2 = 0.66

0

0.1

0.20.3

0.4

0.5

0.6

0.70.8

0.9

1

0 0.2 0.4 0.6 0.8 1

SPOT 4

EgyptSat‐1


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SAVI

The L coefficient is normally estimated at 0.5 however it is being used as 0.25.

)()1)((

LRIRLRIRSAVI

+++−

=

• SAVI is developed to reduce the effect of the soil background


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SAVI

R2 = 0.82

00.1

0.20.3

0.40.50.6

0.70.8

0.91

0 0.2 0.4 0.6 0.8 1

Landsat ETM

EgyptSat‐1

R2 = 0.78

00.1

0.20.3

0.40.5

0.60.7

0.80.9

1

0 0.2 0.4 0.6 0.8 1

SPOT 4

EgyptSat‐1


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Limitations / Uncertainties• There are limitations of EgyptSat1 to be used in

many indices such as: GVI, WDVI, etc. due to: – EgyptSat1 XS images are in Green, Red and NIR

only. – The MIR band has different spatial resolution, that

could not integrated with the XS images. • There is no well defined methodology for

radiometric corrections of EgyptSat1 images, this might explains the high correlation with other VIs


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Conclusion - 1EgyptSat1 is a LEO satellite that provides the local community with high spatial resolution imagesIt has limited spectral resolutions, however, the available channels are suitable for many applicationsThe regular availability of the data could create a monitoring system of the vegetation coverIt efficiently used for computing the vegetation indices and estimated the vegetation coverWhen VIs compared with SPOT 4 & Landsat ETM, they showed high correlation


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Conclusion - 2To precisely rely on this correlation, there is a need for standard method of radiometric corrections of EgyptSat1 imagesFurther in-situ and image processing work are required to see if the little discrepancies in the spectral width of the red and infrared channels between EgyptSat1 and other both SPOT and ETM+ might create differencesFurther work is needed to explore the suitability of EgyptSat1 images in other indices such as soil wetness


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performance of intrinsic vegetation indices from …egypt - us workshop on space technology and...

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