For a full description of the data set please refer to “Global seasonal Sentinel-1 interferometric coherence and backscatter data set”. Josef Kellndorfer, Oliver Cartus, Marco Lavalle, Christophe Magnard, Pietro Mililo, Shadi Oveisgharan, Batu Osmanoglu, Paul Rosen, Urs Wegmüller. doi: 10.1038/s41597-022-01189-6 (opens in new tab)
The dataset contains three main data records:
The 1 x 1 degree tiles of the data set form the basic units of produced image data. All computed metrics are stored as image files in GeoTIFF format where the extent of the images covers exactly 1 degree in longitude and 1 degree in latitude with the origin of the upper left pixel at a full degree in latitude and longitude respectively. All GeoTIFFs have 3 arcseconds resolution in both dimensions and are output to a geographic reference system based on the WGS84 ellipsoid (EPSG:4326). Thus, each file in a tile has a raster dimension of 1,200 pixels by 1,200 lines. For all images, no data values are coded as the digital number zero. Global coverage encompasses a total number of 25,334 tiles.
Tiles in the dataset are labeled by the upper left coordinate of each 1×1 degree tile. Each tile contains the following metrics (based on available polarization covering a tile) as a GeoTiff file.
List of GeoTIFF image products and data conversion to digital numbers in a tile. No data value for all products is the digital number zero (0).
|Mean seasonal backscatter amplitudes γ⁰ (AMP)||Polarizations:|
HH, VV, HV, VH
|Scaled to 16bit unsigned interger with:|
DN=10.0^((dB+83.0)/20.0) where: dB= 10*log10(γ⁰)
|Median seasonal 6,12,18,24,36,48-days repeat-pass coherences (COHxx)||Polarizations:|
|Coherence ρ scaled to 8bit unsigned integer with:|
|Seasonal coherence decay-model parameters ρ∞, τ, and RMSE (rho, tau, rmse)||Polarizations:|
|ρ∞, τ, RMSE scaled to 16bit unsigned integer with:|
|Local incidence angle (inc)||Per relative orbit||DN=Degrees (8bit unsigned integer)|
|Layover/shadow mask (lsmap)||Per relative orbit||8bit unsigned integer where:|
1 – No Shadow or Layover
5 – Layover
17 – Shadow
21 – Shadow in Layover
Virtual Raster Tables (VRT) are available for each seasonal mosaic of a given metric such as the 12-days coherence for the (northern hemisphere) summer or the mosaic of backscatter at VH polarization in winter. In addition, global VRTs are provided which contain all seasonal mosaics of a given metric.
For visualization purposes, external overviews were produced on these files at four overview levels reducing the full resolution global mosaic by two-dimensional down-sampling with averaging by factors of 3×3, 9×9, 27×27, and 81×81. The external overview files are identified by having a filename identical to the global mosaics with the additional postfix “.ovr” appended.
From the global VRTs, downsampled cloud-optimized GeoTIFFs (COG) were generated with built-in overviews. Sample spacing in these mosaics are 0.01 degrees on both longitudinal and latitudinal directions.