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Inter-Sensor Validation of NDVI time series from AVHRR, SPOT-Vegetation, SeaWIFS, MODIS, and LandSAT ETM+ - PowerPoint PPT Presentation


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Inter-Sensor Validation of NDVI time series from AVHRR, SPOT-Vegetation, SeaWIFS, MODIS, and LandSAT ETM+. Molly E. Brown + Jorge E. Pinzon + Jeffery T. Morisette x Kamel Didan* Compton J. Tucker x + SSAI, NASA Goddard Space Flight Center * Soil, Water and Environmental Sciences

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Inter-Sensor Validation of NDVI time series from AVHRR, SPOT-Vegetation, SeaWIFS, MODIS, and LandSAT ETM+

Molly E. Brown +

Jorge E. Pinzon+

Jeffery T. Morisettex

Kamel Didan*

Compton J. Tuckerx

+ SSAI, NASA Goddard Space Flight Center * Soil, Water and Environmental Sciences

Greenbelt, MD 20771 University of Arizona

xNASA Goddard Space Flight Center

Greenbelt, MD 20771

Molly E. Brown, PhD


Overview l.jpg
Overview

  • Data used in study

    • Global NDVI datasets, LandSAT ETM+ for comparison

  • Methods

    • Spectral, spatial and temporal considerations

    • Global 1 degree datasets

    • CEOS sites and drought locations

  • Results

  • Discussion – data continuity from AVHRR through MODIS to VIIRS

Molly E. Brown, PhD


Vis nir swir band comparison l.jpg
VIS/NIR/SWIR Band Comparison

VGT

SeaWiFS

AVHRR

MODIS

Differences in spectral range will necessitate increased processing in

AVHRR and SPOT due to water vapor sensitivity.

Molly E. Brown, PhD


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Data

Molly E. Brown, PhD


Validation methods 59 sites l.jpg

CEOS Land Validation Sites

Validation Methods:59 Sites

  • Aggregations to monthly time step and 1 degree resolution for pixel by pixel comparison.

  • Global hemispherical means created to provide direct comparison of NDVI behavior.

  • Comparisons of time series created from 25x25 km box at native temporal and spatial resolutions: CEOS sites, locations of droughts, deserts, agricultural production regions, etc.

  • Anomaly and seasonal characteristics evaluated

  • Atmospherically corrected, 25x25km subsets of selected LandSAT ETM+ scenes provide a base for comparison of datasets.

Molly E. Brown, PhD



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  • Global averages show that

  • Four sensors have similar

  • signals.

  • Improvements in AVHRR

  • NDVI have reduced many

  • differences between the

  • sensors, enabling a direct

  • comparison between the

  • records:

    • Longer base means for anomaly

    • Multiple data sources for NDVI

    • More work to be done for

    • data integration to be operational

Molly E. Brown, PhD


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Results from CEOS Sites: Harvard, Massachusetts

Correlations:

AV-SP 0.89

AV-MO 0.84

AV-SW 0.86

Note: similarity in range, seasonality of NDVI

LandSAT scene range of variation

Differences in treatment of winter, clouds

Molly E. Brown, PhD


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Correlations:

AV-SP 0.85

AV-MO 0.82

AV-SW 0.66

Correlations:

AV-SP 0.59

AV-MO 0.65

AV-SW 0.59

Molly E. Brown, PhD


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+

Correlations

AV-SP 0.60

AV-MO 0.33

AV-SW 0.38

MODIS cloud and aerosol atmospheric correction

explains the differences between MODIS and the other sensors.

Molly E. Brown, PhD



Conclusions l.jpg
Conclusions

  • Many lessons have been learned from the creation of a consistent NDVI record from AVHRR

    • How to integrate sensors with different gains (NOAA 7-14 and NOAA 16-17)

    • Overcome sensor limitations to reduce clouds, reduce noise and improve image coherence

  • More work to be done on further integrating the records of AVHRR, MODIS, SPOT, SeaWIFS to maximize their various strengths, minimizing their weaknesses

  • AVHRR – MODIS – VIIRS data continuity will be required to maximize length of record to answer important science questions

Molly E. Brown, PhD


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  • Thanks go to Brad Doorn, Assaf Anyamba and Jennifer Small for providing the SPOT data, Gene Feldman, Norman Kuring and Jacques Descloitres for the monthly global SeaWIFS data.

  • URLs:

    • GIMMS NDVIg: http://landcover.org

    • SeaWIFS: http://daac.gsfc.nasa.gov/data/dataset/SEAWIFS_LAND

    • MODIS: http://edcdaac.usgs.gov/modis/dataproducts.asp

    • SPOT VGT: http://free.vgt.vito.be/

    • Subsets of SPOT, AVHRR, MODIS tiles, and Landsat ETM+ data at CEOS sites: http://landval.gsfc.nasa.gov/MODIS/index.php

      Thank you!

Molly E. Brown, PhD