PRISMA system is necessary for generation of the following products based on captured Satellite images:
• Level 0: Raw data rearranged to basic 30x30 Km images
• Level 1: radiometrically and spectrally adjusted Images (radiance to the Top of the Atmosphere)
• Level 2: atmospherically and geometrically adjusted Images
Level 0 products are obtained by processing the raw data downloaded from the satellite, decompressing the instrument packages and rearranging them into blocks corresponding to 1000 consecutive lines (about 30x30km) and overlapping the PAN and hyperspectral channels.
Such products are kept in the system together with location information, with the image characteristics and a thumbnail RGB, to allow the catalog search and are available for superior products generation and related direct distribution to 'interested users.
Level 0 product returns all ancillary data generated by the instrument and the platform associated with the image, is in binary format and keeps the original 12-bit instrument coding.
Due to its characteristics, this product is suitable for a very specialized use, since such processing needs very sophisticated data manipulation and the knowledge of both methods and parameters required to calibrate the picture.
The Level 1 products are obtained by processing the level 0 product and applying the spectral and radiometric corrections, both for PAN and all hyperspectral channels.
The result is a spectrum of spectral radiance at the Top of the Atmosphere (TOA spectral radiance).
Attached to the Spectral Image are also some auxiliary and thematic maps. in particular:
• Cloud Mask: the mask of pixels covered by clouds
• Sun-glint Mask: the mask of the pixels affected by sun-glint
• Surface classification Map: the map of the type of surface for each pixel so divided:
- vegetated surface:
- Meadows / Pastures
- Forests / Woods
- Marshes / swamps
- non-vegetated surfaces
- Snow / Ice
The product is in HDF-EOS format and reports all the calibration parameters that were used and the platform ancillary information as well as the image of radiance at the TOA and auxiliary listed maps.
The product is intended for a specialized useage (eg. Scientific), as it shows the measurement of spectral radiance at the Top of the Atmosphere (TOA) which still includes the distorting effect of the atmosphere. In addition, the image is still in the instrument coordinates and therefore requires further geometric processing to use the product in application mode.
Level 2 products are obtained by processing the level 1 products and applying atmospheric and geometric corrections.
The level 2 products are of three types:
- Level 2b: spectral radiance to the surface
- 2c level: surface reflectance
- 2d level: geocoded surface reflectance
All products include both the PAN channel and the hyperspectral channels and are in HDF-EOS format.
2b- and 2c-level Products are obtained by removing the distorting effects of the atmosphere and are geo-referenced, i.e. they are still in the instrument coordinates, but report the information needed to determine the geographic location of the image pixel.
Associated with the image of spectral reflectance, 2c level product also contains auxiliary maps related to:
- Concentration of the columnar atmospheric water vapor and, where possible, the maps related to:
- optical thickness and Angstrom exponent of atmospheric aerosol
- optical thickness of identified thin clouds
Finally, Level-2 Product is the geocoded version, thus projected in a cartographic UTM WGS84 reference, of Layer-2c PAN and hyperspectral images.
The level 2 products can better be used for application purposes, since they already contain geophysical information.