1. Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra 29-30 Nov 2000 1 THE VEGA 2000 data set description of data properties (draft) Compiled by E. Bartholomé, JRC Ispra

2. Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra 29-30 Nov 2000 2 SOURCES of INFORMATION

3. Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra 29-30 Nov 2000 3 Main sources of Information  The VEGETATION portal : http://www.spot-vegetation.com  The VEGETATION web site at CNES: http://vegetation.cnes.fr  the Users Guide: http://www.spotimage.fr/data/images/vege/VEGETAT/book_1/e_frame.htm  Henry & al 2000: VEGETATION image performances, (Belgirate)  Passot 2000: VEGETATION image processing methods in the CTIV (Belgirate)  Saint 1998: the VEGETATION Programme

4. Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra 29-30 Nov 2000 4 Technical description of the system VEGETATION homepage at CNES: http://vegetation.cnes.fr:8080/

5. Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra 29-30 Nov 2000 5 The users manual On-line: http://www.spotimage.fr/data/images/vege/VEGETAT/book_1/e_frame.htm stand-alone downloadable version: http://vegetation.cnes.fr:8080/system/content.html#perfos

6. Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra 29-30 Nov 2000 6 GENERAL DESCRIPTION

7. Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra 29-30 Nov 2000 7 VEGETATION onboard SPOT 4

8. Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra 29-30 Nov 2000 8 The VEGETATION instrument IMAGE SPECTRAL BANDS :Blue - Red - NIR - SWIR (Red, NIR and SWIR identical to HRVIR ones) CODING : 10 bits OPTICS :telecentric lenses F.O.V. :101° (ground swath = 2250 km) DETECTION :CCD line array RESOLUTION :1.165 X 1.165 km²

9. Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra 29-30 Nov 2000 9 Radiometry: specs & calibration

10. Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra 29-30 Nov 2000 10 Main specs of the VEGETATION system - radiometry Four spectral bands Blue0.43 - 0.47 µmNear InfraRed0.78 - 0.89 µm Red0.61 - 0.68 µmShortWave InfraRed1.58 - 1.75 µm G. Saint, 1998

11. Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra 29-30 Nov 2000 11 Main specs of the VEGETATION system - radiometry Calibration interband and multitemporal : better than 3% absolute : better than 5% through : * on-board calibration device to measure evolution with time *calibration campaigns Henry & al, 2000 - Belgirate

12. Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra 29-30 Nov 2000 12 Calibration methods  Pre-flight measurements (absolute)  On-board calibration lamp (multitemporal and multi-angular)  Vicarious calibration over test sites (absolute)  Calibration over the Rayleigh scattering (absolute)  Calibration over desert sites (multitemporal and multi-angular)  Calibration over the sun glint (interband)  Calibration over clouds (interband)  Calibration over snowy sites (multi-angular)  VGT/HRVIR intercalibration using simultaneous viewing (Henry & al., Belgirate, 2000)

13. Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra 29-30 Nov 2000 13 Evolution of sensor sensitivity Henry & al, 2000 - Belgirate

14. Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra 29-30 Nov 2000 14 Sensor calibration: an example Henry & al, 2000 - Belgirate

15. Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra 29-30 Nov 2000 15 Sensor calibration: overall conclusions Absolute calibration : – B0 : 4% - B2 : 4% - B3 : 5% - SWIR : ? Multitemporal calibration : – better than 2% Interband calibration : – B2/B3 : 2% - B2/B0 : 3% - B2/SWIR : ? Intercalibration with HRVIR – B2 : 3% - B3 : 2% - SWIR : 2% Henry & al, 2000 - Belgirate

16. Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra 29-30 Nov 2000 16 The MIR sensors Brazil - 23 May 99 Blue/NIR/SWIR SWIR defective detectors Henry & al, 2000 - Belgirate

17. Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra 29-30 Nov 2000 17 The MIR sensors  InGaAs CCDs are sensitive to protons (irradiation tests carried out in 1999)  Radiation effects: detector dark current increases and becomes unstable Henry & al, 2000 - Belgirate

18. Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra 29-30 Nov 2000 18 Instrument resolution

19. Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra 29-30 Nov 2000 19 Main specs of the VEGETATION system - reolution êSpatial resolution 1km in the entire field of view êOff nadir observations up to 50°

20. Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra 29-30 Nov 2000 20 Stable across-swath ground resolution G. Saint, 1998

21. Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra 29-30 Nov 2000 21 Spatial resolution: pre-flight MTF measurement http://vegetation.cnes.fr:8080/system/mtf.htm

22. Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra 29-30 Nov 2000 22 Spatial resolution: in-flight FTM measurement MTF estimation using simultaneous HRVIR image as reference: Very good consistency with pre-flight measurements Henry & al, 2000 - Belgirate

23. Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra 29-30 Nov 2000 23 Actual effect of angular viewing on resolution Niger Delta, Dec 1, 1999: close to nadir Dec 3, 1999: close to swath edge

24. Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra 29-30 Nov 2000 24 Product geometry

25. Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra 29-30 Nov 2000 25 Main specs of the VEGETATION system - geometry êDistorsions :  multispectral < 0.1 km multitemporal < 0.3 km  absolute location ~ 0.5 km registration with HRVIR < 0.3km

26. Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra 29-30 Nov 2000 26 The VEGETATION geometric correction (1)  A) Straight geometrical modelling that takes into account êthe satellite location  computed from an orbit bulletin (MADRAS)  or from real time on board navigator (DORIS), êattitude movements  computed from the gyrometers data êinstrument geometrical characteristics, (measured before launch, and recalibrated in orbit):  the payload positioning on SPOT4  the 4 cameras positioning on the payload  the pixel viewing directions, taking into account the lenses distorsion (see next slide), specific for each camera qGeometrical modelling is made for the B3 band qOther bands pixels are located by difference to B3 (dl,dp) Passot, 2000 - Belgirate

27. Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra 29-30 Nov 2000 27 The VEGETATION geometric correction (2)  B) Manual and assisted GCP pointing (from March 99) to fix the absolute satellite attitude error êFrom a 3650 GCPs data base  built from VEGETATION image chips previously pinpointed with SPOT HRV images.  Seasonal effects are taken into account êAttended operations :  selection of 10 to 20 GCPs per orbit, chosen on non cloudy locations  or propagation to the next orbit of the computed bias Passot, 2000 - Belgirate

28. Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra 29-30 Nov 2000 28 Consequence on temporal superimposition Observed location of AVHRR pixels in a time series, after D. Meyer, IJRS  Registrations êMultispectral : <0.2 km êMultitemporal : <<0.5 km for one year  Absolute location <0.8 km 1 km IFOV Multitemporal Field of View Expected accuracy for VEGETATION G. Saint, 1998

29. Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra 29-30 Nov 2000 29 observed geometric stability S10 NDVI product S1 NDVI product

30. Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra 29-30 Nov 2000 30 Principle of data mapping  Map projection in Plate-Carrée : êElevation corrections using a Digital Elevation Model (ETOPO5), interpolating between the 2 location grids at 0 and 5000m elevation êCartographic coordinates computed with the Geolib IGN library êBicubic interpolation on a 4x4 window Raw data 1.15 to 1.6 km step Map Projected area 1km step Passot, 2000 - Belgirate

31. Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra 29-30 Nov 2000 31 Computing ground reflectances

32. Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra 29-30 Nov 2000 32 Computation of TOA reflectance êNormalization using parameters computed in QIV (cf calibration methods) êInterpolation of bad detectors : SWIR blind or defective detectors êRadiance computed using absolute calibration parameters from QIV êReflectance computed with a solar irradiance model, taking into account sun angles, and sun-earth distance êComputation of TOA NDVI for temporary use in the synthesis process Passot, 2000 - Belgirate

33. Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra 29-30 Nov 2000 33 Atmospheric correction êUsing the SMAC CESBIO software : a simplified implementation of 6S, tuned for VEGETATION spectral bands êUsing water vapor data : short term forecasts, 4 deliveries/day from Meteo-France êUsing climatology of ozone (CESBIO) êUsing simple static models for aerosols (CESBIO) êUsing a 8km resolution DEM for pressure estimation êAtmospherical parameters are calculated on 8km x 8km cells, then interpolated / pixel Passot, 2000 - Belgirate

34. Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra 29-30 Nov 2000 34 Case study: the VEGA 2000 data set

35. Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra 29-30 Nov 2000 35 Geometric properties of the VEGA 2000 data set Coverage of the global window: Upper left: -180°,75° Bottom right: 180°,-56° Projection: lat-long (“plate-carrée”) Ellipsoid: WGS 84 Pixel size: 1/112 DEG = 0.0089285714 image size: 40320 x 14673 pixels (global coverage)

36. Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra 29-30 Nov 2000 36 Accurate data georeferencing

37. Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra 29-30 Nov 2000 37 S1 Daily coverage Distance between 2 successive paths at equator: 375 km Saint 1998

38. Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra 29-30 Nov 2000 38 S1: areas of overlap Combination based on NDVI max

39. Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra 29-30 Nov 2000 39 Varying coverage extension in N. latitudes 1-10 Jan 2000 1-10 Jul 2000 Sun azimuth angle must be < 80°

40. Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra 29-30 Nov 2000 40 Water mask Strait of Messina

41. Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra 29-30 Nov 2000 41 Content of data set Total volume per pixel: 16 bytes Users manual

42. Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra 29-30 Nov 2000 42 Data coding (1) Reflectance channels (B0, B2, B3, Mir) NDVI Users manual

43. Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra 29-30 Nov 2000 43 Data coding (2) Users manual

44. Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra 29-30 Nov 2000 44 Users manual

45. Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra 29-30 Nov 2000 45 Status map

46. Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra 29-30 Nov 2000 46 Status map Users manual

47. Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra 29-30 Nov 2000 47 That’s all folks… (for today!)