Introduction to Satellite Derived Vegetation Indices
Rishiraj DuttaSpace Application Section
Information and Communication Technology & Disaster Risk Reduction Division
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Introduction to the Use of Geospatial Information Technology for Drought Risk Management13-17 November, 2017
Tonle Bassac II Restaurant, Phnom Penh, Cambodia
What is Vegetation Index?
A Vegetation Index is an indicator thatdescribes the greenness — the relativedensity and health of vegetation — for eachpixel in a satellite image. (Laymen Definition)
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Reference: https://phenology.cr.usgs.gov/ndvi_foundation.php
What is Vegetation Index? (Contd.…)
Some mathematical combination ortransformation of spectral bands thataccentuates the spectral properties of greenplants so that they appear distinct fromother image features. (Scientific Definition)
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What Vegetation Indices Does?
•Indicate the AMOUNT of vegetation (e.g.,%cover, LAI, biomass, etc.);
•Distinguish between soil and vegetation;•Reduce atmospheric and topographiceffects if possible.
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Spectral Reflectance Curve
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Improved Reflectance Curve by NASA
Normalized Difference Vegetation Index (NDVI)•To determine density of green vegetation;•Observe the distinct colors of visible and near-infrared light reflected by the plants.
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False Color Composite (FCC) of a satellite image showing thedifferent characteristics of the image features
Reference: http://www.cawa-project.net/system/files/image/story/body_img/ScreenShot_rapidEye.png
NDVI (Contd.…)• NDVI calculated from the visible and
near-infrared light reflected byvegetation;
• Healthy vegetation (left) absorbs most ofthe visible light that hits it, and reflects alarge portion of the near-infrared light;
• Unhealthy or sparse vegetation (right)reflects more visible light and less near-infrared light.
United Nations Economic and Social Commission for Asia and the Pacific 7Reference: https://earthobservatory.nasa.gov/Features/MeasuringVegetation/measuring_vegetation_2.php
NDVI Range• NDVI for a given pixel always result in a number that
ranges from minus one (-1) to plus one (+1);• No green leaves gives a value close to zero. A zero
means no vegetation and;• High NDVI Values, +1 (0.8 - 0.9) indicates healthy
vegetation;• Low NDVI values, -1 indicates less or no vegetation.
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NDVI for the period from March to October 2017Source: GISTDA
Period of Coverage: Mar/Apr/May/Jul/Oct
Mapping Paddy Areas in Cambodia
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Kandal & Prey Veng Province Wet Season 2010 (MODIS) Kandal & Prey Veng Province Dry Season 2010 (MODIS)
Deshapriya et al., 2010
Brief Methodology Used
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Comparison of Paddy Area from MODIS based Results and Ground based Statistics
Crop Intensity Map
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Kandal & Prey Veng Province Crop Intensity Map 2010 (MODIS)
Deshapriya et al., 2010
Paddy Area Distribution
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Paddy Area Distribution in Cambodia for Wet Season (2014)
Paddy Area Comparison of MODIS based result and ground statistics in Cambodia for Wet Season
Deshapriya et al., 2010
Normalized Difference Water Index (NDWI)• Satellite-derived index estimating the leaf water
content at canopy level;• Derived from the Near-Infrared (NIR) and Short Wave
Infrared (SWIR) channels;• NDWI product: varies between -1 to +1.
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NDWI (Contd.…)• High values of NDWI
• Correspond to high vegetation water content and to high vegetation fractioncover
• Low NDWI values• Correspond to low vegetation water content and low vegetation fractioncover.
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NDWI for the period from March to October 2017Source: GISTDA
Period of Coverage: Mar/Apr/May/Jun/Jul/Oct
Soil Adjusted Vegetation Index (SAVI)•Modification of the NDVI to correct theinfluence of soil brightness when vegetativecover is low;
•SAVI is structured similar to the NDVI butwith the addition of a “soil brightnesscorrection factor”.
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SAVI (Contd.…)
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Reference :A joint project of the USDA-ARS Jornada Experimental Range, the BLM-AIM Program, and the Idaho Chapter of The Nature Conservancy
Vegetation Condition Index (VCI)• Compares the current NDVI to the range of values
observed in the same period in previous years;• VCI expressed in %;• Lower and higher values indicate bad and good
vegetation state conditions, respectively.
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Reference: http://land.copernicus.eu/global/products/vci
VCI Global (NOAA AVHRR) , 4 km, 7-day Composite
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Reference: http://www.ospo.noaa.gov/Products/land/vhp/VCI.html
4th November (Week of 44)
Greenness (NDVI) 2014
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18-March-2014 15-April-2014 20-May-2014 17-June-2014
22-July-2014 19-August-2014 16-September-2014 21-October-2014
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Drought Situation in Cambodia (2014)
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18-March-2014 15-April-2014 20-May-2014 17-June-2014
22-July-2014 19-August-2014 16-September-2014 21-October-2014
Reference: https://www.star.nesdis.noaa.gov/smcd/emb/vci/VH/vh_browseByCountry.php
Where can you find Satellite data for DroughtStudies?NOAA AVHRR (1-km & 4-km, 7-day Composite)https://www.star.nesdis.noaa.gov/smcd/emb/vci/VH/index.phpUSGS Earth Explorerhttps://earthexplorer.usgs.gov/Landsat Data Accesshttps://landsat.usgs.gov/landsat-data-accessLand Processes Distributed Active Archive Centerhttps://lpdaac.usgs.gov/data_access/data_pool/
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