Minimize VGT-S processing

The aim of VGT-S1 processing is to produce a daily or 10 days 1km SPOT-VEGETATION-like product (VGT-S1 or VGT-S10). This compositing is carried out on the VEGETATION Plate-Carrée projection grid with a resolution of 1 km at equator. The global VEGETATION grid is defined from 180W to 180E and from 56S to 75N with a regular latitude-longitude sampling grid with 112 pixels per degree.

The daily composite is produced from a set of SY_2_VGK track products. The longitude/latitude location of each VGK pixel is used to select the corresponding pixel in the output Plate-Carrée grid (equi-rectangular projection).

The pixels incorporated into the synthesis are selected according to the maximum NDVI value, in order to ensure coverage of all landmasses worldwide with a minimum effect of cloud cover. The surface reflectance and annotation of the VGK pixel corresponding to the maximum NVDI is copied in the VGT-S1 product. The daily resulting product is called SY_2_VG1.

The VGT-S10 compositing processing is similar to the daily processing except that the inputs are daily products (SY_2_VG1) instead of track products. This means that the only difference is the way to get the geo-location pixel from the input pixels. The resulting product is called SY_2_V10.

Note that, in the frame of coming evolutions, the composite method used to create VGT-S1 and S10 products will be investigated and modified to ensure continuity to VGT and Proba-V service. Two options are under investigation:

  1. Analyse the more adequate composite method between several known technics ( the Best Index Slope Extraction or Mean Compositing methods, …) and implement it in the VGT-S processing.
  2. Update the NDVI computation and discuss the "max NDVI" composite method.