THE VEGA 2000 dataset description of data properties

THE VEGA 2000 dataset description of data properties

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

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

Global Vegetation Monitoring Unit 3 Technical description of the system VEGETATION homepage at CNES: http://vegetation.cnes.fr:8080/ The VEGA 2000 Data set - main properties E. bartholom, GLC 2000 Workshop, Ispra 29-30 Nov 2000 Space Applications Institute Global Vegetation Monitoring Unit 4 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

The VEGA 2000 Data set - main properties E. bartholom, GLC 2000 Workshop, Ispra 29-30 Nov 2000 Space Applications Institute Global Vegetation Monitoring Unit 5 GENERAL DESCRIPTION The VEGA 2000 Data set - main properties E. bartholom, GLC 2000 Workshop, Ispra 29-30 Nov 2000 Space Applications Institute Global Vegetation Monitoring Unit 6

VEGETATION onboard SPOT 4 The VEGA 2000 Data set - main properties E. bartholom, GLC 2000 Workshop, Ispra 29-30 Nov 2000 Space Applications Institute Global Vegetation Monitoring Unit 7 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 km The VEGA 2000 Data set - main properties E. bartholom, GLC 2000 Workshop, Ispra 29-30 Nov 2000 Space Applications Institute Global Vegetation Monitoring Unit 8 Radiometry: specs & calibration The VEGA 2000 Data set - main properties E. bartholom, GLC 2000 Workshop, Ispra 29-30 Nov 2000

Space Applications Institute Global Vegetation Monitoring Unit 9 Main specs of the VEGETATION system - radiometry Blue Red NIR SWIR Typical vegetation reflectance Typical soil reflectance 0.14 0.12 Relative response Near InfraRed 0.78 - 0.89 m

ShortWave InfraRed 1.58 - 1.75 m 0.10 0.6 0.5 0.4 0.08 0.3 0.06 0.2 0.04 0.1 0.02 0.00 400

Reflectance Four spectral bands Blue 0.43 - 0.47 m Red 0.61 - 0.68 m 500 600 700 800 G. Saint, 1998 The VEGA 2000 Data set - main properties E. bartholom, GLC 2000 Workshop, Ispra 29-30 Nov 2000

0 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 Wavelength Space Applications Institute Global Vegetation Monitoring Unit 10 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 The VEGA 2000 Data set - main properties E. bartholom, GLC 2000 Workshop, Ispra 29-30 Nov 2000 Space Applications Institute Global Vegetation Monitoring Unit 11 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) The VEGA 2000 Data set - main properties E. bartholom, GLC 2000 Workshop, Ispra 29-30 Nov 2000 Space Applications Institute Global Vegetation Monitoring Unit 12 Evolution of sensor sensitivity VEGETATION Sensitivity variation measured with the on-board lamp 6,00 4,00 Variation (%) 2,00

0,00 24/03/98 -2,00 02/07/98 10/10/98 18/01/99 28/04/99 06/08/99 14/11/99 22/02/00 -4,00 -6,00 -8,00

B0 -10,00 B2 -12,00 B3 -14,00 SWIR Days Henry & al, 2000 - Belgirate The VEGA 2000 Data set - main properties E. bartholom, GLC 2000 Workshop, Ispra 29-30 Nov 2000

Space Applications Institute Global Vegetation Monitoring Unit 13 Sensor calibration: an example Channel B2 calibration estimated Ak 1.1 Pre-flight Rayleigh Rayleigh HRVIR Deserts White S ands Ak 1.0

La Crau 0.9 0.8 0.7 3/24/98 7/2/98 10/10/98 Henry & al, 2000 - Belgirate The VEGA 2000 Data set - main properties E. bartholom, GLC 2000 Workshop, Ispra 29-30 Nov 2000 1/18/99 4/28/99

8/6/99 11/14/99 2/22/00 Days Space Applications Institute Global Vegetation Monitoring Unit 14 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 The VEGA 2000 Data set - main properties E. bartholom, GLC 2000 Workshop, Ispra 29-30 Nov 2000 Space Applications Institute Global Vegetation Monitoring Unit 15 The MIR sensors SWIR defective detectors Brazil - 23 May 99

Blue/NIR/SWIR Henry & al, 2000 - Belgirate The VEGA 2000 Data set - main properties E. bartholom, GLC 2000 Workshop, Ispra 29-30 Nov 2000 Space Applications Institute Global Vegetation Monitoring Unit 16 The MIR sensors InGaAs CCDs are sensitive to protons (irradiation tests carried out in 1999) Radiation effects: detector dark current increases and becomes unstable VEGETATION SWIR: Evolution of the number of defective detectors as a function of time (24/03/1998 - 19/03/2000) VGT Polynomial (VGT)

100 Number of detectors 90 80 70 60 50 40 30 20 10 0 0 Henry & al, 2000 - Belgirate The VEGA 2000 Data set - main properties E. bartholom, GLC 2000 Workshop, Ispra 29-30 Nov 2000

100 200 300 400 500 Days since the launch 600 700 800 2 y = 6E-05x + 0,0354x + 4,5242

Space Applications Institute Global Vegetation Monitoring Unit 17 Instrument resolution The VEGA 2000 Data set - main properties E. bartholom, GLC 2000 Workshop, Ispra 29-30 Nov 2000 Space Applications Institute Global Vegetation Monitoring Unit 18 Main specs of the VEGETATION system - reolution Spatial resolution 1km in the entire field of view Off nadir observations up to 50

The VEGA 2000 Data set - main properties E. bartholom, GLC 2000 Workshop, Ispra 29-30 Nov 2000 Space Applications Institute Global Vegetation Monitoring Unit 19 Stable across-swath ground resolution G. Saint, 1998 The VEGA 2000 Data set - main properties E. bartholom, GLC 2000 Workshop, Ispra 29-30 Nov 2000 Space Applications Institute Global Vegetation Monitoring Unit

20 Spatial resolution: pre-flight MTF measurement http://vegetation.cnes.fr:8080/system/mtf.htm The VEGA 2000 Data set - main properties E. bartholom, GLC 2000 Workshop, Ispra 29-30 Nov 2000 Space Applications Institute Global Vegetation Monitoring Unit 21 Spatial resolution: in-flight FTM measurement MTF estimation using simultaneous HRVIR image as reference: Very good consistency with pre-flight measurements B2 MTF in-flight estimation 1,2 1

0,8 M TF 0,6 45 0,4 Barcelona Oristano Sassari pre-flight MTF 0,2 0 0 0,1 0,2

0,3 0,4 0,5 fr Henry & al, 2000 - Belgirate The VEGA 2000 Data set - main properties E. bartholom, GLC 2000 Workshop, Ispra 29-30 Nov 2000 Space Applications Institute Global Vegetation Monitoring Unit 22 Actual effect of angular viewing on resolution Niger Delta, Dec 1, 1999: close to nadir

The VEGA 2000 Data set - main properties E. bartholom, GLC 2000 Workshop, Ispra 29-30 Nov 2000 Dec 3, 1999: close to swath edge Space Applications Institute Global Vegetation Monitoring Unit 23 Product geometry The VEGA 2000 Data set - main properties E. bartholom, GLC 2000 Workshop, Ispra 29-30 Nov 2000 Space Applications Institute Global Vegetation Monitoring Unit 24

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

The VEGETATION geometric correction (1) A) Straight geometrical modelling that takes into account the satellite location computed from an orbit bulletin (MADRAS) or from real time on board navigator (DORIS), attitude movements computed from the gyrometers data instrument 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 Geometrical modelling is made for the B3 band Other bands pixels are located by difference to B3 (dl,dp) Passot, 2000 - Belgirate The VEGA 2000 Data set - main properties E. bartholom, GLC 2000 Workshop, Ispra 29-30 Nov 2000 Space Applications Institute Global Vegetation Monitoring Unit 26

The VEGETATION geometric correction (2) B) Manual and assisted GCP pointing (from March 99) to fix the absolute satellite attitude error From a 3650 GCPs data base built from VEGETATION image chips previously pinpointed with SPOT HRV images. Seasonal effects are taken into account Attended 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 The VEGA 2000 Data set - main properties E. bartholom, GLC 2000 Workshop, Ispra 29-30 Nov 2000 Space Applications Institute Global Vegetation Monitoring Unit 27 Consequence on temporal superimposition Expected accuracy for VEGETATION IFOV Multitemporal Field of View 1 km

Registrations Observed location of AVHRR pixels in a time series, after D. Meyer, IJRS Multispectral : <0.2 km Multitemporal : <<0.5 km for one year G. Saint, 1998 Absolute location <0.8 km The VEGA 2000 Data set - main properties E. bartholom, GLC 2000 Workshop, Ispra 29-30 Nov 2000

Space Applications Institute Global Vegetation Monitoring Unit 28 observed geometric stability S10 NDVI product The VEGA 2000 Data set - main properties E. bartholom, GLC 2000 Workshop, Ispra 29-30 Nov 2000 S1 NDVI product Space Applications Institute Global Vegetation Monitoring Unit 29 Principle of data mapping

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

The VEGA 2000 Data set - main properties E. bartholom, GLC 2000 Workshop, Ispra 29-30 Nov 2000 Space Applications Institute Global Vegetation Monitoring Unit 31 Computation of TOA reflectance Normalization using parameters computed in QIV (cf calibration methods) Interpolation of bad detectors : SWIR blind or defective detectors Radiance computed using absolute calibration parameters from QIV Reflectance computed with a solar irradiance model, taking into account sun angles, and sun-earth distance Computation of TOA NDVI for temporary use in the synthesis process Passot, 2000 - Belgirate The VEGA 2000 Data set - main properties

E. bartholom, GLC 2000 Workshop, Ispra 29-30 Nov 2000 Space Applications Institute Global Vegetation Monitoring Unit 32 Atmospheric correction Using the SMAC CESBIO software : a simplified implementation of 6S, tuned for VEGETATION spectral bands Using water vapor data : short term forecasts, 4 deliveries/day from Meteo-France Using climatology of ozone (CESBIO) Using simple static models for aerosols (CESBIO) Using a 8km resolution DEM for pressure estimation Atmospherical parameters are calculated on 8km x 8km cells, then interpolated / pixel Passot, 2000 - Belgirate The VEGA 2000 Data set - main properties E. bartholom, GLC 2000 Workshop,

Ispra 29-30 Nov 2000 Space Applications Institute Global Vegetation Monitoring Unit 33 Case study: the VEGA 2000 data set The VEGA 2000 Data set - main properties E. bartholom, GLC 2000 Workshop, Ispra 29-30 Nov 2000 Space Applications Institute Global Vegetation Monitoring Unit 34 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-carre) Ellipsoid: WGS 84 Pixel size: 1/112 DEG = 0.0089285714 image size: 40320 x 14673 pixels (global coverage) The VEGA 2000 Data set - main properties E. bartholom, GLC 2000 Workshop, Ispra 29-30 Nov 2000 Space Applications Institute Global Vegetation Monitoring Unit 35 Accurate data georeferencing

+1 DEG DEG 112 pixels DEG = 1/2 pixel! The VEGA 2000 Data set - main properties E. bartholom, GLC 2000 Workshop, Ispra 29-30 Nov 2000 Space Applications Institute Global Vegetation Monitoring Unit 36 S1 Daily coverage

Saint 1998 Distance between 2 successive paths at equator: 375 km The VEGA 2000 Data set - main properties E. bartholom, GLC 2000 Workshop, Ispra 29-30 Nov 2000 Space Applications Institute Global Vegetation Monitoring Unit 37 S1: areas of overlap Combination based on NDVI max The VEGA 2000 Data set - main properties E. bartholom, GLC 2000 Workshop, Ispra 29-30 Nov 2000

Space Applications Institute Global Vegetation Monitoring Unit 38 Varying coverage extension in N. latitudes 1-10 Jan 2000 1-10 Jul 2000 Sun azimuth angle must be < 80 The VEGA 2000 Data set - main properties E. bartholom, GLC 2000 Workshop, Ispra 29-30 Nov 2000 Space Applications Institute Global Vegetation Monitoring Unit 39

Water mask Strait of Messina The VEGA 2000 Data set - main properties E. bartholom, GLC 2000 Workshop, Ispra 29-30 Nov 2000 Space Applications Institute Global Vegetation Monitoring Unit 40 Content of data set Total volume per pixel: 16 bytes Users manual The VEGA 2000 Data set - main properties E. bartholom, GLC 2000 Workshop,

Ispra 29-30 Nov 2000 Space Applications Institute Global Vegetation Monitoring Unit 41 Data coding (1) Reflectance channels (B0, B2, B3, Mir) NDVI Users manual The VEGA 2000 Data set - main properties E. bartholom, GLC 2000 Workshop, Ispra 29-30 Nov 2000 Space Applications Institute Global Vegetation Monitoring Unit 42

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

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

Global Vegetation Monitoring Unit 46 Thats all folks (for today!) The VEGA 2000 Data set - main properties E. bartholom, GLC 2000 Workshop, Ispra 29-30 Nov 2000 Space Applications Institute Global Vegetation Monitoring Unit 47

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