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Comparison of Green Vegetation Fraction Retrievals from SPOT-VEGETATION and MSG-SEVIRI Sensors

This study compares Green Vegetation Fraction (GVF) retrievals from SPOT-VEGETATION and MSG-SEVIRI sensors. Results show differences in NDVI and GVF data. SPOT-VEGETATION and MSG-SEVIRI sensors, data formats, and products are analyzed in detail.

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Comparison of Green Vegetation Fraction Retrievals from SPOT-VEGETATION and MSG-SEVIRI Sensors

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  1. Comparison of Green Vegetation Fraction Retrievals from SPOT-VEGETATION and MSG-SEVIRI Sensors Bernard LACAZE (1) and Aydin ERTÜRK (2) • CNRS UMR 8586 PRODIG Pôle de Recherche pour l’Organisation et la Diffusion de l’Information Géographique, Paris, France • Turkish State Meteorological Service, Remote Sensing Division, Ankara, Turkey

  2. SPOT-VEGETATION and MSG-SEVIRI NDVI data SPOT-VEGETATION : deriving Green Vegetation Fraction (GVF) from scaled NDVI MSG-SEVIRI : deriving GVF from spectral unmixing or scaled NDVI Results : Comparison of dekadal NDVI and GVF data (MSG-SEVIRI and SPOT-VEGETATION) Conclusion Outline IGARSS 2011 24-29 July, Vancouver, Canada

  3. SPOT-VEGETATION sensor (since 1998) SPOT-4 and SPOT-5 sun synchronous orbit altitude 822 km return interval 1 day swath width 2250km IGARSS 2011 24-29 July, Vancouver, Canada

  4. SPOT-VEGETATION 10-daily NDVI S10 :Maximum Value Compositing IGARSS 2011 24-29 July, Vancouver, Canada

  5. SPOT-VEGETATION 10-daily NDVI NDVI data : HDF format, 1 byte/pixel Real NDVI = 0.004 * Digital Number -0.1 Status map : HDF format, 1 byte /pixel IGARSS 2011 24-29 July, Vancouver, Canada

  6. MSG-SEVIRI sensor (since 2004) MSG-1 and MSG-2 SEVIRI one image every 15mn Spinning Enhanced Visible and Infrared Imager resolution at nadir 3km (1km for channel 12) IGARSS 2011 24-29 July, Vancouver, Canada

  7. Land surface monitoring products are elaborated by EUMETSAT Land Surface Analysis Satellite Application Facility (LSA SAF) Lisbon, Portugal : NDVI is not a standard product of LSA SAF (vegetation parameters = FVC, LAI, FAPAR) daily NDVI derived from LSA-SAF spectral albedos is available from AMMASAT data base (area= West Africa, spatial resolution 0.05°, daily since september 2005) daily experimental NDVI data available from EUMETSAT, since February 2011 (+ pre-operational data from 2010 : 176 days, elaborated with Turkish State Metorological Service) MSG-SEVIRI daily NDVI products IGARSS 2011 24-29 July, Vancouver, Canada

  8. MSG – SEVIRI NDVI daily data since sept. 2005 AMMASAT database • covered area: West Africa25° W to 25° E, 20° N to 5° S • resolution 0.05°  1000 samples x 500 lines • daily data since septembre 2005 • NDVI calculatedfrom spectral albedosproduced by LSA-SAF (BRDF model Roujeanet al., 1992, k0parameter), model fitted over 5 days) • NetCDF format, integer, NDVI*10000, NDVI≥0, -1 = ocean

  9. MSG – SEVIRI NDVI monthly synthesis january 2010 AMMASAT database

  10. MSG – SEVIRI NDVI daily data Turkish State Met. Service pre-operational data (2010) • covered area: whole MSG disk • MSG native projection  3712 samples x 3712 lines • 176 days (February-August 2010) • NDVI calculatedfrom top of atmospherereflectances, with BRDF correction (dailymean, maximum and minimum NDVI, number of obervations) • HDF5 format, byte, NDVI*100, NDVI≥0

  11. MSG-SEVIRI NDVI 10-daily synthesis 0 0.7 Maximum NDVI 20-30 March 2010 IGARSS 2011 24-29 July Vancouver, Canada

  12. MSG-SEVIRI NDVI 10-daily synthesis 21-31 May 2007 0 0.7 Maximum NDVI 20-30 March 2010 IGARSS 2011 24-29 July Vancouver, Canada

  13. MSG – SEVIRI NDVI daily data NDVE :Eumetsat experimental data (2011) • covered area: whole MSG disk • MSG native projection  3712 samples x 3712 lines • daily data sinceFebruary 2011 • NDVI calculatedfrom top of atmospherereflectances, with BRDF correction • HDF5 format, with 899 bytes header

  14. MSG – SEVIRI NDVI daily data Eumetsat experimental data (2011) surface type = IGBP land cover classification

  15. GVF is the fraction of green vegetation covering a unit area of horizontal soil, varying from 0 (bare soil) to 1 (full cover) GVF is independent of leaf and soil optical properties although it is defined with reference to green elements It is generally close to FAPAR (varying from 0 to 0.95) with the advantage of being defined independently of illumination conditions, making it an intrinsic canopy attribute for these reasons, GVF is a very good candidate for substitution of classical vegetation indices like NDVI From NDVI to Green Vegetation Fraction IGARSS 2011 24-29 July, Vancouver, Canada

  16. SPOT-VEGETATION : GVF is named fCover and available since October 2009 from Geoland 2 BIOPAR products database (archived data to be available end of 2011) ; Geoland2 is carried out in the context of GMES, a initiative of the European Commission, which aims to build up a European capacity for Global Monitoring of Environment and Security; other sites for obtaining or disseminating data : GEOSUCCESS, VGT4Africa, EUMETCAST, DevCoCast MSG-SEVIRI: daily GVF (named FVC Fraction of Vegetation Cover) is an operational product since March 2007 available from LSA SAF archive http://landsaf.meteo.pt/ Availability of Green Vegetation Fraction data IGARSS 2011 24-29 July, Vancouver, Canada

  17. Deriving Green Vegetation Fraction (Fcover) from SPOT-VEGETATION data scaled NDVI BioPar Product User Manual (2010) IGARSS 2011 24-29 July, Vancouver, Canada

  18. Deriving Green Vegetation Fraction (Fcover) from SPOT-VEGETATION data NDVIsoil = min (NDVImin, 0.14) NDVImax = 0.85 BioPar Product User Manual (2009) IGARSS 2011 24-29 July, Vancouver, Canada

  19. Green Vegetation Fraction (FCover) from SPOT-VEGETATION data Fcover : 30-days composite, updated every 10 days using a sliding window ADDITIONAL DATA: FCover-ERR (estimated uncertainty) SMB (Status Map or Quality Flag) NMOD (number of clear observations) LMK (Land cover map = GLC 2000 Global Land Cover Map) BioPar Product FCover IGARSS 2011 24-29 July, Vancouver, Canada

  20. Green Vegetation Fraction (FCover) from SPOT-VEGETATION data 10° x 10° tiles GVF data available since oct. 2009; archived data available end of 2011 BioPar Product FCover IGARSS 2011 24-29 July, Vancouver, Canada

  21. Green Vegetation Fraction (FCover) from SPOT-VEGETATION : West Africa, July 1-10, 2010 DN 0-250 = FVC*250 DN=255 : Invalid Example of SPOT-VEGETATION 10-daily GVF BioPar Product FCover IGARSS 2011 24-29 July, Vancouver, Canada

  22. Deriving Green Vegetation Fraction (FVC) from MSG-SEVIRI data EUMETSAT • The operational daily product FVC is based on the three short-wave channels (VIS 0.6µm, NIR 0.8µm, SWIR 1.6µm) using as input the k0 parameter of a parametric BRDF model (Roujean et al., 1992) • The algorithm relies on an optimised Spectral Mixture Analysis (SMA) technique. In a first step, an exhaustive training set for the soil and vegetation components is defined. Second, a Gaussian Mixture Model is fit to the training data. Third, a Bayesian model selection is used to compute the relative likelihood of membership in each soil/vegetation single-model. FVC is then estimated using a linear-weighted combination single-model estimate IGARSS 2011 24-29 July, Vancouver, Canada

  23. Daily Green Vegetation Fraction (FVC) from MSG-SEVIRI data EUMETSAT 4 sub-images HDF5 format IGARSS 2011 24-29 July, Vancouver, Canada

  24. 10-day SPOT-VEGETATION S10 NDVI MVC, resampled at 0.025° resolution Maximum of 10 daily NDVI values, MSG-SEVIRI experimental product, resampled at 0.025° resolution (daily mean of n available data during each day) Results : comparison of NDVI products Example : 1-10 July 2010, West Africa area IGARSS 2011 24-29 July, Vancouver, Canada

  25. Results : SPOT-VEGETATION NDVI S10 Example : 10-day NDVI (1-10 July 2010), West Africa area DN Cloud contaminated pixels IGARSS 2011 24-29 July, Vancouver, Canada

  26. Results : SPOT-VEGETATION NDVI Example : 10-day NDVI (1-10 July 2010), West Africa area cloudy pixels (from status map) in white DN IGARSS 2011 24-29 July, Vancouver, Canada

  27. Results : MSG NDVI Example : 10-day NDVI (1-10 July 2010), West Africa area maximum of 10 daily mean values NDVI x NDVI x 100 IGARSS 2011 24-29 July, Vancouver, Canada

  28. Comparison of SPOT-VEG and MSG NDVI Example : 10-day NDVI (1-10 July 2010), West Africa area Histograms of NDVI values (cloud-free pixels only) SPOT-VEG MSG-SEVIRI IGARSS 2011 24-29 July, Vancouver, Canada

  29. Comparison of SPOT-VEG and MSG NDVI Example : 10-day NDVI (1-10 July 2010), West Africa area cloud-free pixels only MSG SPOT-VEG IGARSS 2011 24-29 July, Vancouver, Canada

  30. 10-daily SPOT-VEGETATION FVC(Geoland 2 BioPar FVC), resampled at 0.025° resolution Mean of 10 daily MSG-SEVIRI operational product FVC (LSA-SAF) , resampled at 0.025° resolution Mean of 10 daily MSG-SEVIRI scaled NDVI, using threshold values NDVImin = 0.098 and NDVI max = 0.71 ( values proposed by NOAA-NESDIS, Bob YU pers. comm.) Results : comparison of FVC products Example : 1-10 July 2010, West Africa area IGARSS 2011 24-29 July, Vancouver, Canada

  31. BioPar Product FCover Results : SPOT-VEG GVF (scaled NDVI) Example : 10-day FCOVER (1-10 July 2010), West Africa area grey= no vegetation cover (GVF = 0) ; white = invalid data GVF (%) BioPar Product FCover IGARSS 2011 24-29 July, Vancouver, Canada

  32. Results : MSG-SEVIRI GVF (LSA SAF FVC) mean of daily FCOVER (1-10 July 2010), West Africa area Grey= no vegetation cover (GVF=0) GVF (%) derived from FVC product IGARSS 2011 24-29 July, Vancouver, Canada

  33. Comparison of SPOT-VEG and MSG GVF Example : 10-day GVF 1-10 July 2010), West Africa area Cloud-free pixels with GVF>0 only GVFmsg = 0.85 * GVFspot-veg + 10.49 r2 = 0.86 IGARSS 2011 24-29 July, Vancouver, Canada

  34. Comparison of SPOT-VEG and MSG GVF Example : all Africa, years 2008,2009 IGARSS 2011 24-29 July, Vancouver, Canada

  35. Results: MSG-SEVIRI GVF(scaled NDVI) mean of daily GVF (1-10 July 2010), West Africa area Grey= no vegetation cover GVF (%) GVF (%) NDVImin = 0.098; NDVImax = 0.71 (NOAA-NESDIS, 2011) IGARSS 2011 24-29 July, Vancouver, Canada

  36. Comparison of SPOT-VEG and MSG FVC Example : 10-day GVF 1-10 July 2010), West Africa area Cloud-free pixels with GVF>0 only MSG GVFmsg = 0.71 * GVFspot-veg + 17.88 r2 = 0.67 SPOT-VEG IGARSS 2011 24-29 July, Vancouver, Canada

  37. Comparison SPOT-VEG vs MSG GVF Example : desert pixels (GVF = 0) yellow : GVF = 0 for both data sources orange : only GVF SPOT-VEG=0 SPOT-VEG and MSG (FVC from LSA-SAF) SPOT-VEG and MSG (GVF from scaled NDVI) IGARSS 2011 24-29 July, Vancouver, Canada

  38. It is suggested to make use of Green Vegetation Fraction as a substitute to NDVI Both SPOT-VEGETATION (10-daily) and MSG-SEVIRI (daily) GVF data can be obtained on a near real-time basis: status of products = operational MSG-SEVIRI has lower spatial resolution than SPOT-VEG, but provides a higher number of available observations in regions with high cloud occurrence, and can be used for high temporal resolution monitoring (1 to 5 days) Conclusions 1 IGARSS 2011 24-29 July, Vancouver, Canada

  39. Different procedures are used to extract FVC from spectral data: all methods suppose that atmospheric and BRDF corrections are efficient Discrepancies between GVF results from MSG and SPOT-VEG are observed, mainly overestimation of GVF in arid areas when using MSG data Further research is needed to validate FVC estimations and to ensure intercomparability of results between MSG, SPOT-VEG, MODIS, METOP,… using preferably the same preprocessing/ processing methods to derive GVF Conclusions 2 IGARSS 2011 24-29 July, Vancouver, Canada

  40. Thank you for your attention lacaze.bernard@gmail.com Télédétection peer-reviewed electronic open-access journal http://www.teledetection.net IGARSS 2011 24-29 July, Vancouver, Canada

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