Level-1 Product Formatting - Sentinel-1 SAR Technical Guide - Sentinel Online
Level-1 Product Formatting
The top-level Sentinel-1 product folder name is composed of upper-case alphanumeric characters separated by an underscore (_).
Product Naming Convention
The Mission Identifier (MMM) denotes the satellite and will be either S1A for the Sentinel-1A instrument or S1B for the Sentinel-1B instrument.
The Mode/Beam (BB) identifies the S1-S6 beams for SM products and IW, EW and WV for products from the respective modes.
Product Type (TTT) can be RAW, SLC, GRD or OCN.
Resolution Class (R) can be F (Full resolution), H (High resolution), M (Medium resolution) or _ (underscore: not applicable to the current product type); Resolution Class is used for GRD only.
The Processing Level (L) can be 0, 1 or 2.
The Product Class can be Standard (S) or Annotation (A). Annotation products are only used internally by the PDGS and are not distributed.
Polarisation (PP) can be:
- SH (single HH polarisation)
- SV (single VV polarisation)
- DH (dual HH+HV polarisation)
- DV (dual VV+VH polarisation)
- HH (Partial Dual polarisation, HH only)
- HV (Partial Dual polarisation, HV only)
- VV (Partial Dual polarisation, VV only)
- VH (Partial Dual polarisation, VH only)
The product start and stop date and times are shown as fourteen digits representing the date and time, separated by the character 'T'.
The absolute orbit number at product start time (OOOOOO) will be in the range 000001-999999.
The mission data-take identifier (DDDDDD) will be in the range 000001-FFFFFF. The product unique identifier (CCCC) is a hexadecimal string generated by computing CRC-16 on the manifest file. The CRC-16 algorithm used to compute the unique identifier is CRC-CCITT (0xFFFF).
The folder extension is always "SAFE".
Within a product folder, measurement data sets and annotation data sets follow a similar naming convention with lower case alphanumeric characters separated by a dash (-).
Dataset Naming Convention
The Mission Identifier (mmm) denotes the satellite and will be either s1a for the Sentinel-1A instrument or s1b for the Sentinel-1B instrument.
The Swath Identifier (sss) identifies the s1-s6 beams for SM mode, iw1-iw3 for IW mode, ew1-ew5 for EW more and wv1-wv2 for WV mode.
Product Type (ttt) can be raw, slc, grd or ocn.
Polarisation (pp) can be:
- hh (single HH polarisation)
- vv (single VV polarisation)
- hv (single HV polarisation)
- vh (single VH polarisation).
The product start and stop date and times are shown by fourteen digits representing the date and time separated by the character 't'.
The absolute orbit number at product start time (oooooo) will be in the range 000001-999999.
The mission data-take identifier (dddddd) will be in the range 000001-FFFFFF.
The image number (nnn) identifies each individual image. WV vignettes each have their own image number as do each swath and polarisation image for SM, IW and EW.
The file extension denotes the data format of the file and could be tiff, nc, xml, html, kml, xsd or png.
Sentinel-SAFE File Format
Sentinel data products are distributed using a Sentinel-specific variation of the Standard Archive Format for Europe (SAFE) specification. The SAFE format has been designed to act as a common format for archiving and conveying data within ESA Earth Observation archiving facilities. SAFE was recommended for the harmonization of the GMES missions by the GMES Product Harmonisation Study.
The Sentinel-SAFE format wraps a folder containing image data in a binary data format and product metadata in XML. This flexibility allows the format to be scalable enough to represent all levels of Sentinel products.
A Sentinel product refers to a directory folder that contains a collection of information. It includes:
- a manifest.safe file which holds the general product information in XML
- subfolders for measurement data sets containing image data in various binary formats
- a preview folder containing quicklooks in PNG format, Google Earth overlays in KML format and HTML preview files
- an annotation folder containing the product metadata in XML as well as calibration data
- a support folder containing the XML schemes describing the product XML
The data delivered is packaged as a file structure containing a manifest file in XML format listing general product metadata and subfolders for measurement data, annotations, previews and support files (the number of subfolders is reduced for raw data).
Product Folder File Structure
The manifest file is an XML file containing the mandatory product metadata common to all Sentinel-1 products.
Annotated data sets contain metadata describing the properties and characteristics of the measurement data or how they were generated. For each band of data there is a product annotation data set that contains metadata describing the main characteristics corresponding to that band such as the state of the platform during acquisition, image properties, polarisation, Doppler information, swath merging and geographic location. Calibration annotations contain calibration information and the beta nought, sigma nought, gamma and digital number look-up tables that can be used for absolute product calibration. Noise data annotations contain the estimated thermal noise look-up tables. Annotated data sets are provided in XML format.
In the preview folder, quicklook data sets are power detected, averaged and decimated to produce a lower resolution version of the image. Single polarisation products are represented with a grey scale image. Dual polarisation products are represented by a single composite colour image in RGB with the red channel (R) representing the co-polarisation VV or HH), the green channel (G) represents the cross-polarisation (VH or HV) and the blue channel (B) represents the ratio of the cross an co-polarisations.
Representation data sets found in the support folder contain information about the format or syntax of the measurement and annotated data sets and can be used to validate and exploit these data. Representation data sets are provided as XML schemas.
Measurement data sets contain the binary information of the actual acquired or processed data. For Level-0 this is the instrument data, for Level-1 it is processed data. There is one measurement data set per polarisation and per swath. TOPSAR SLC products contain one complex measurement data set in GeoTIFF format per sub-swath per polarisation. Level-1 GRD products contain one detected measurement data set in GeoTIFF format per polarisation.
For further details on the Sentinel-1 Level-1 product formatting, please refer to the Sentinel-1 Level-1 and Level-2 Product Specification document found in the document library.