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

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

Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra Nov Main sources of Information  The VEGETATION portal :  The VEGETATION web site at CNES:  the Users Guide:  Henry & al 2000: VEGETATION image performances, (Belgirate)  Passot 2000: VEGETATION image processing methods in the CTIV (Belgirate)  Saint 1998: the VEGETATION Programme

Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra Nov Technical description of the system VEGETATION homepage at CNES:

Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra Nov The users manual On-line: stand-alone downloadable version:

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

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

Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra Nov 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 km²

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

Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra Nov Main specs of the VEGETATION system - radiometry Four spectral bands Blue µmNear InfraRed µm Red µmShortWave InfraRed µm G. Saint, 1998

Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra Nov 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, Belgirate

Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra Nov 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)

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

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

Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra Nov 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, Belgirate

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

Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra Nov 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, Belgirate

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

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

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

Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra Nov Spatial resolution: pre-flight MTF measurement

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

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

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

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

Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra Nov 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, Belgirate

Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra Nov 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, Belgirate

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

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

Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra Nov 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, Belgirate

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

Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra Nov 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, Belgirate

Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra Nov 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, Belgirate

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

Space Applications Institute Global Vegetation Monitoring Unit The VEGA 2000 Data set - main properties E. bartholomé, GLC 2000 Workshop, Ispra Nov 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 = image size: x pixels (global coverage)

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

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

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

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

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

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

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

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

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

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

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

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