Minimize Product Grid

Two types of grids are defined for SLSTR outputs:

  • the measurement grids, also called instrument reference frame,
  • the image grids.

In addition, each grid contains a number of variations according to the different instrument view and resolution. All SLSTR L1B and L2 files are defined on the image grid. The L0 product is still associated with the instrument grid.

SLSTR products are generated separately in two instrument views:

  • nadir view is almost vertical at the sub-satellite point
  • oblique view has a local zenith angle close to 55°.

Two resolutions are then defined:

  • a 500 m resolution for Visible/NIR/SWIR channels (S1 to S6)
  • a 1 km resolution for thermal and fire channels (S7 to S9, F1 to F2).

The measurement grids are the native grids on which SLSTR collects data. Each datum is indexed by scan, pixel and detector numbers. The scan number identifies the number of the scan line, starting at the ascending node crossing (ANX). The pixel number identifies, in a scan line, the pixel count, starting at one end. The detector number identifies which detector element of the channel made the measurement.

The image grid is locally Cartesian and regular, aligned with the sub-satellite track. All measurement data are provided on this grid to hold an "image-like" data and to be compliant with the continuity requirement (i.e. SLSTR granules are continuous).

In addition to these two grids, a lower resolution grid is defined and called the tie-point grid. Some annotations such as meteorological or viewing geometry data are produced on this grid. It is aligned with the 1 km and 0.5 km image grids and is regular in distance across track (16 km) and regular in time along track (1 km to fulfill the continuity requirement).

The F1 channel has its own grid because it uses detectors that are not aligned with the other 1 km thermal detectors.