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Global Seasonal Sentinel-1 Interferometric Coherence and Backscatter Dataset

Data Records

The dataset contains three main data records:

  1. 1 x 1-degree tiles. Each tile contains GeoTIFFs at 3 arcsec pixel spacing of all metrics available in the tile.
  2. Global Virtual Raster Tables (VRT) with external overview files of seasonal backscatter, coherence, rho, tau, and rmse including VRT stacks of seasons.
  3. Global mosaicked tiles as cloud optimized GeoTIFFs at 0.01-degree pixel spacing for each of the computed metrics

Naming and Organization of 1 x 1-degree tile data

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.

 

  • Tile naming convention
    • Tile identifiers (TILEID) in the data set are labeled by the upper left coordinate of each 1×1 degree tile using North (N) and South (S), and East (E) and West (W) qualifiers.
    • Examples
      • N48W090 covers the area of 47°-48° northern latitude and 90°-89° degrees western longitude
      • S01E012 covers the area of 1°-2° southern latitude and 12°-13° degrees eastern longitude
  • File naming convention for backscatter, coherence, and model parameter files
    • <TILEID>_<SEASON>_<POLARIZATION>_<METRIC>.tif
      • TILEID = Identifier of tile referenced to upper left tile corner
      • SEASON = winter, spring, summer, or fall (referring to Northern hemisphere seasons)
      • POLARIZATION = vv, vh, hh, or hv
      • METRIC = AMP, COHxx, rho, tau, rmse
        • xx = 06, 12, 18, 24, 36, 48
    • Examples
      • N49E012_winter_vv_COH06.tif
      • N49E012_spring_vv_COH48.tif
      • N49E012_summer_vh_AMP.tif
  • File naming convention for incidence angle and layover/shadow files
    • <TILEID>_<000><F>_<METRIC>.tif
      • TILEID = Identifier of tile referenced to upper left tile corner
      • 000 = Relative orbit number from 001 to 175
      • F = A or D for ascending or descending flight direction
      • METRIC = inc or lsmap
    • Example
      • N49E012_095D_inc.tif

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.

Winter
winter_vv_AMPwinter_hh_AMP
winter_vh_AMPwinter_hv_AMP
winter_vv_COH06winter_hh_COH06
winter_vv_COH12winter_hh_COH12
winter_vv_COH18winter_hh_COH18
winter_vv_COH24winter_hh_COH24
winter_vv_COH36winter_hh_COH36
winter_vv_COH48winter_hh_COH48
winter_vv_rhowinter_hh_rho
winter_vv_rmsewinter_hh_rmse
winter_vv_tauwinter_hh_tau
Spring
spring_vv_AMPspring_hh_AMP
spring_vh_AMPspring_hv_AMP
spring_vv_COH06spring_hh_COH06
spring_vv_COH12spring_hh_COH12
spring_vv_COH18spring_hh_COH18
spring_vv_COH24spring_hh_COH24
spring_vv_COH36spring_hh_COH36
spring_vv_COH48spring_hh_COH48
spring_vv_rhospring_hh_rho
spring_vv_rmsespring_hh_rmse
spring_vv_tauspring_hh_tau
Summer
summer_vv_AMPsummer_hh_AMP
summer_vh_AMPsummer_hv_AMP
summer_vv_COH06summer_hh_COH06
summer_vv_COH12summer_hh_COH12
summer_vv_COH18summer_hh_COH18
summer_vv_COH24summer_hh_COH24
summer_vv_COH36summer_hh_COH36
summer_vv_COH48summer_hh_COH48
summer_vv_rhosummer_hh_rho
summer_vv_rmsesummer_hh_rmse
summer_vv_tausummer_hh_tau
Fall
fall_vv_AMPfall_hh_AMP
fall_vh_AMPfall_hv_AMP
fall_vv_COH06fall_hh_COH06
fall_vv_COH12fall_hh_COH12
fall_vv_COH18fall_hh_COH18
fall_vv_COH24fall_hh_COH24
fall_vv_COH36fall_hh_COH36
fall_vv_COH48fall_hh_COH48
fall_vv_rhofall_hh_rho
fall_vv_rmsefall_hh_rmse
fall_vv_taufall_hh_tau

 

 

Data Conversion to Digital Numbers (Tile Data)

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).

Metric Format
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:
HH, VV
Coherence ρ scaled to 8bit unsigned integer with:
DN=ρ*100
Seasonal coherence decay-model parameters ρ, τ, and RMSE (rho, tau, rmse)Polarizations:
HH, VV
ρ, τ, RMSE scaled to 16bit unsigned integer with:
DN= ρ/τ/RMSE*1000
Local incidence angle (inc)Per relative orbitDN=Degrees (8bit unsigned integer)
Layover/shadow mask (lsmap)Per relative orbit8bit unsigned integer where:
1 – No Shadow or Layover
5 – Layover
17 – Shadow
21 – Shadow in Layover

 

Naming and Organization of Virtual Raster Tables

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.

    • File naming conventions for seasonal single metric VRTs
      • Global_<SEASON>_<POLARIZATION>_<METRIC>.vrt
        • SEASON = winter, spring, summer, or fall (referring to Northern hemisphere seasons)
        • POLARIZATION = vv, vh, hh, or hv
        • METRIC = AMP, COHxx, rho, tau, rmse
          • xx = 06, 12, 18, 24, 36, 48
      • Examples
        • Global_spring_vv_COH06.vrt
        • Global_winter_vh_AMP.vrt
    • File naming conventions for all-season VRT stacks
      • Global__<POLARIZATION>_<METRIC>.vrt
        • POLARIZATION = vv, vh, hh, or hv
        • METRIC = AMP, COHxx, rho, tau, rmse
          • xx = 06, 12, 18, 24, 36, 48
      • Examples
        • Global__vv_COH06.vrt
        • Global__hh_AMP.vrt

Naming and Organization of global GeoTiff Mosaics with 0.01-degree sample spacing

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.

  • File naming convention for global 0.01-degree sample spacing GeoTiffs
    • Global_<SEASON>_<POLARIZATION>_<METRIC>_100ppd.tif
      • SEASON = winter, spring, summer, or fall (referring to Northern hemisphere seasons)
      • POLARIZATION = vv, vh, hh, or hv
      • METRIC = AMP, COHxx, rho, tau, rmse
        • xx = 06, 12, 18, 24, 36, 48
    • Examples
      • Global_spring_vv_COH06_100ppd.tif
      • Global_fall_vv_rho_100ppd.tif
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