Some preliminary tests on VGT data over France J-L CHAMPEAUX, L FRANCHISTEGUY, S. GARRIGUES CNRM/GMME/MATIS.

Some preliminary tests on VGT data over France

J-L CHAMPEAUX, L FRANCHISTEGUY, S. GARRIGUES

CNRM/GMME/MATIS

Cloud mask evaluation

Status map cloud mask.

New VITO cloud mask (Lissens and al, Belgirate 2000) with thresholds tuned over the world applied to TOA reflectance: a pixel is declared clear if B0<493 OR SWIR<180.

New tuned cloud mask with thresholds tuned over France for surface reflectance (S1 data): a pixel is declared cloudy if B0>=220 AND SWIR>=180

Comparison between:

What strategy for the cloud mask?

• use the status map (poor quality)

• use the VITO thresholds Must be applied to TOA reflectances

• determine new thresholds on B0 for specific window

Work on bidirectional effects:

• Evaluation of bidirectional effects in different solar-target-sensor configurations over homogeneous landcover areas

• Implementation and test of BDC method (B.Duchemin, CESBIO)

• Proposal VEGA2000: Determination of global albedo from VGT products

VEGA2000 proposal : Determination of global albedo products from VGT instrument data for use in numerical weather forecast and climate models.L. FRANCHISTEGUY(CNRM/GMME) 

  Preliminary study with a data set of VGT-P products (April 1998 – March 1999)  a)      Atmospheric corrections : SMACTOA reflectances surface reflectances

b)      BRDF kernel-driven model inversion : correction of bidirectional effects (30 days compositing period with a sliding periodof 10 days).  c) Retrieval of land surface albedo (directional albedo) for a 100*100 km domain located in southeast part of France.

Method for retrieval of surface properties

Inversion of a BRDF model :

s, v, = k0 + k1 f1s, v, + k2 f2s, v,

(model of Roujean et al., 1992)

K0: Normalized reflectance for s=0 and v=0

DECIDUOUS PIXELS ( South of France)

AA

Unsupervised classification using 10 days MVC ( from 1/1/2000 to 31/09/2000 over SO France

Corine Land Cover dataset at 1km resolution

Unsupervised classification using 10 days MVC from 1/1/2000 to 31/09/2000 over SO France