Sentinel-1 Global Mosaics

Level-1 Ground Range Detected (GRD) products consist of focused SAR data that has been detected, multi-looked and projected to ground range using the Earth ellipsoid model WGS84. The ellipsoid projection of the GRD products is corrected using the terrain height specified in the product general annotation. The terrain height used varies in azimuth and it is constant in range (For IW/EW modes only the terrain height of first subswath is considered)

The mosaics have four bands of data (Red (B04), Green (B03), Blue (B02) and wide band Near Infrared (B08)). First, cloud masking based on the scene classification layer of the Sentinel-2 level 2 algorithm was applied, then for each pixel and band, within three-month time periods, the first quartile of the distribution of the pixel values was taken as the output value to filter out any bright pixels misclassified as not clouds. If there are no valid pixels for the given timeframe, the pixel is left empty. Sentinel-2 cloudless mosaics can be used for various purposes such as land cover classification, land use planning, or for the creation of basemaps. These images are especially useful for showing large and cloudy areas with interesting large-scale patterns. Iceland is a prime example, with frequent cloud cover and large areal extent spanning several Sentinel-2 swaths.

The Level-1C product is composed of 110x110 km2 tiles (ortho-images in UTM/WGS84 projection). Earth is subdivided on a predefined set of tiles, defined in UTM/WGS84 projection and using a 100 km step. However, each tile has a surface of 110x110 km² in order to provide large overlap with the neighbouring. The Level-1C product results from using a Digital Elevation Model (DEM) to project the image in cartographic geometry. Per-pixel radiometric measurements are provided in Top Of Atmosphere (TOA) reflectances along with the parameters to transform them into radiances.

This collection offers Sentinel-1 Level-1 Single Look Complex (SLC) products captured in the modes Interferometric Wide Swath (IW), Extra Wide Swath (EW), and Strip Map Mode (SM). Level-1 SLC products are images in the slant range by azimuth imaging plane, in the image plane of satellite data acquisition. Each image pixel is represented by a complex (I and Q) magnitude value and therefore contains both amplitude and phase information. Each I and Q value is 16 bits per pixel. The processing for all SLC products results in a single look in each dimension using the full available signal bandwidth. The imagery is geo-referenced using orbit and attitude data from the satellite. SLC images are produced in a zero Doppler geometry. This convention is common with the standard slant range products available from other SAR sensors.

Global, cloud-free, and reconstructed historical Landsat spectral bands are provided at a spatial resolution of 30 meters and temporal resolution of bimonthly intervals from 1997 onwards. The dataset was generated using the GLAD Landsat ARD version 2 as the primary input for temporal aggregation and the imputation of missing values.

The Sentinel-2 GRI STAC collection provides a multi-layer Level-1C “Global Reference Image” composed of B04 (red) band plus corresponding quality masks, derived from a multi-layer L1B GRI for improved geometric consistency.