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LAND PRODUCT VALIDATION update

F. Baret, J. Nightingale, S. Garrigues, J. Nickeson Missoula, 17 June 2009. LAND PRODUCT VALIDATION update. Outline. CEOS LPV context and structure Guidelines for best practices The way forward …. CEOS/WGCV/LPV.

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LAND PRODUCT VALIDATION update

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  1. F. Baret, J. Nightingale, S. Garrigues, J. Nickeson Missoula, 17 June 2009 LAND PRODUCT VALIDATION update

  2. Outline CEOS LPV context and structure Guidelines for best practices The way forward …

  3. CEOS/WGCV/LPV • CEOS (committee on Earth Observation Satellite): group of space agencies aiming at harmonizing their activities at the international level. • Composed of several working groups (WG) including WG on Calibration and Validation (WGCV). • WGCV is made of several subgroups: • - IVOS (Infrared and Visible Optical Sensors) • - Microwave • - SAR • - Terrain Mapping • - Atmospheric Chemistry • - Land Product Validation (LPV)

  4. Mission Statement & Goals • To foster quantitative validation of higher level global land products derived from remote sensing data • To relay results to users • To develop and promote international standards and protocols for field sampling, scaling, error budgeting, data exchange • To provide feed-back to international structures (GEO/GEOSS, GCOS, GTOS, IGBP …) for : • product definition, accuracy and quality assurance • Requirements for future missions

  5. Role of LPV within ECVs • Essential Climate Variables (ECVs) are recognized to play a key role: • within international scientific structures (GCOS, GTOS) • international convention for verification (UNFCCC) to complement/compare with national (official) figures • Strong requirements on the evaluation of product uncertainties: need coordinated and consensus validation efforts mandatory for all the ECVs

  6. Implementation tools • CEOS has no proper funding mechanisms • Actions based on best efforts by space agencies • CEOS provides recommendations to space agencies… • Possible direct actions on satellite data access • Direct actions within the community • Synergizing existing projects • Initiating new projects • Mostly a bottom-up approach

  7. Products targeted • Land cover with GOFC-GOLD • Fire (mainly burnt area) with GOFC-GOLD • Biophysical variables (LAI, fAPAR) • Albedo, BRDF, surface reflectance • Land Surface Temperature and emissivity (with IVOS) • Soil moisture • Biomass? In discussion with GOFC-GOLD • Snow?

  8. LPV proposed new structure sub-groups by product family with leads from the community if possible from different continents • Albedo: G. Schaepman & C. Schaaf • Land-Cover: M. Herold & M. Friedl • Fire: K. Tansey & L. Boschetti • Vegetation: R. Fernandes, S. Plummer, J. Nightingale • Land Surface Temperature & emissivity: S. Hook & J. Sobrino • Soil: W. Wagner & T. Jackson

  9. Role of sub-group leads • Coordinate the validation activities at the global level: • Guideline for best practices • Lead the writing of a guideline document for best practices on validation • Ensures community consensus and publication/distribution • Ensures that the document is updated when new data / methods are available • Validation activities: promote their development/implementation • Data sharing • Data compilation • Implementation of validation exercise • Publication/distribution of results • Convey information to and from the community • Plans/Status/Results of the validation towards CEOS/international organizations/community

  10. Communication tools + LPV Web site http://lpvs.gsfc.nasa.gov+ LPV Wiki http://lpvs.pbworks.com/+ LPV Listservs

  11. Outline CEOS LPV context and structure Guidelines for best practices The way forward …

  12. Best practices guidelines document • The “best practices guidelines” should be: • Based on current knowledge, tools, data and methods • Tested and easily repeatable • The Best Practices guidelines document should: • Define the best practices including data and methods to conduct validation of a satellite-derived land product. • Be a “living” document that is updated as tools, data, methods are improved through scientific endeavour • Process for Endorsement by CEOS/ community • Peer reviewprocess

  13. Proposed common structure

  14. Validation and intercomparison ‘validation’ is the process of quantitatively defining the system response to known, controlled signal inputs. ‘Validation’ refers to assessing the uncertainty of higher level, satellite sensor derived products by analytical comparison to reference data, which is presumed to represent the target value. ‘Intercomparison’ of data products provides an initial indication of gross differences and possibly insights into the reasons for the differences. (Justice et al. 2000) Validation and intercomparison are mandatory and complementary Validation allows ‘absolute’ quantification of uncertainties but often limited by the number and quality of available reference data Intercomparison provides a more exhaustive evaluation of consistencies/differences Required by users required when combining several products

  15. Products definition and uncertainties • Products definition: ECVs not always very clearly defined (GCOS/GTOS documents). • Need more process model related defintions • Feedback to GCOS/GTOS • Required uncertainties attached to ECVs not defined in a traceable way • Need more process related uncertainties evaluation • Threshold / Optimal / Target ? • Feedback to GCOS/GTOS

  16. Data sets for validation: sites • Distribution of sites: must be representative of surface types, state/conditions • systematic (FRA 2010) • stratified Existing data sets Albedo: 19 BSRN sites LAI/fAPAR: 80-100 sites Need to capitalize the information Land cover: 4300 points

  17. Data sets for validation: measurements Reference measurements - interpretation by experts based on HSR images (land-cover, fire) - quantitative measurements (albedo, LAI-fAPAR, LST&E , moisture) - definition of the variable measured - footprint and scaling Need for high spatial resolution images (Landsat/SPOT)

  18. Global validation Metrics used: Land cover : accuracy /user-producer Confusion matrix … LAI-fAPAR: RMSE, weighed RMSE, biases … Users need more information on the structure of uncertainties

  19. Satellite data for intercomparison - Definition of variables: LCCS … - Spatial sampling exhaustive (Land cover) systematic stratified (LAI, fAPAR, Albedo …) - Spatial support area need to get same projection / resolution - Temporal support period need to get synchronous / same resolution Degradation oforiginal characteristics

  20. Global intercomparison Land cover

  21. Global intercomparison: LAI • Temporal continuity • Temporal consistency

  22. Smoothness of temporal evolution • Statistical distributions

  23. Scatterplots

  24. Current status Level 4: operational validation Land cover Level 3 Biophysical Moisture Level 2 Fire Albedo LST & E Level 1

  25. Operational Validation: land cover

  26. Operational Validation: Biophysical

  27. Concluding remarks • Very strong ECV context • Need funding mechanisms for sustainable validation activities: validation costs!! • Importance of reference measurements: • data sharing • improved cooperation with existing/developing networks • Availability of high spatial resolution images • A lot of new products … and not all at the ultimate validation level …. very challenging • Mandatory for product improvement / combination

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