Minimize VGT P Product

The Level-2 VGP SYN product, SY_2_VGP, is an output from the SYNERGY Level-2 processor and contains 1 km VEGETATION-like product TOA reflectances.

All VGT continuity geophysical data are calculated for the same regular latitude-longitude sampling (equivalent to a Plate Carrée projection) with a longitudinal sampling distance at the Equator of 1 km square. The 1 km sampling has 112 pixels per degree (see the figure below) for a global map ranging from 56°S to 75°N. Pixel coordinates in this map are illustrated by the green square in figure below.

SPOT VGT 1 km Plate Carrée Grid Cell

This product is referenced as SPOT continuity product, adapted for scientific applications requiring highly accurate physical measurements. As a consequence, data are corrected for systematic errors (such as error registration of the different channels or calibration of all the detectors along the line-array detectors for each spectral band) and resampled to predefined geographic projections.

The series of SPOT VGT products to be replicated within the SYN branch of SENTINEL-3 processing consists of the physical (VGT P), daily synthesis (VG1) and 10-day synthesis (V10) SAFE products. All products contain datasets of TOA reflectance (VGT P) or surface reflectance (VGT S) for the channels listed in the table below.

 

CHANNEL SPECTRAL REGION CENTRAL WAVELENGTH (nm) WAVELENGTH RANGE (nm)
B0 Blue 450 430 - 470
B2 Red 645 610 - 680
B3 NIR 835 780 - 890
MIR SWIR 1 665 1 580 - 1 750
VGT spectral bands

The VGT-P SAFE product includes annotation data for the geometric viewing and illumination conditions, the total water vapour and ozone columns, and the aerosol optical depth. All annotation data are provided on a sub-sampled grid, where the sub-sampling of every 16th pixel preserves the spatial resolution of the sub-sampled annotation datasets at Level-1C, which is every 64th pixel.

Some specific Level-2 flags are also included as annotation data files. They are listed in the table below, resulting in 1 byte of status information per pixel.

 

FLAG MASK FLAG VALUE FLAG MEANING DESCRIPTION
3 0 clear Indicates cloud-free pixels.
3 1 shadow Indicates pixels shad-owed by clouds.
3 2 uncertain Indicates uncertain cloud detection.
3 3 cloud Indicates cloudy pixels.
4 4 ice_or_snow Indicates ice or snow.
8 8 land Indicates land.
16 16 MIR_good Quality of MIR measurement is good.
32 32 B3_good Quality of B3 measurement is good.
64 64 B2_good Quality of B2 measurement is good.
128 128 B0_good Quality of B0 measurement is good.
VGT status flags