# Source: Sentinel 1 Radiometrically Terrain Corrected (RTC)
# Type: cog
# Catalog: STACConnector
# Generated by: folia catalog import
# Generated at: 2026-02-08T00:48:49.409815+00:00
#
# Do not edit manually - will be overwritten on next import.

source:
  id: planetary-computer-sentinel-1-rtc
  name: Sentinel 1 Radiometrically Terrain Corrected (RTC)
  type: cog
  url: https://planetarycomputer.microsoft.com/api/stac/v1/collections/sentinel-1-rtc
  description: 'The [Sentinel-1](https://sentinel.esa.int/web/sentinel/missions/sentinel-1)
    mission is a constellation of two polar-orbiting satellites, operating day and
    night performing C-band synthetic aperture radar imaging. The Sentinel-1 Radiometrically
    Terrain Corrected (RTC) data in this collection is a radiometrically terrain corrected
    product derived from the [Ground Range Detected (GRD) Level-1](https://planetarycomputer.microsoft.com/dataset/sentinel-1-grd)
    products produced by the European Space Agency. The RTC processing is performed
    by [Catalyst](https://catalyst.earth/).


    Radiometric Terrain Correction accounts for terrain variations that affect both
    the position of a given point on the Earth''s surface and the brightness of the
    radar return, as expressed in radar geometry. Without treatment, the hill-slope
    modulations of the radiometry threaten to overwhelm weaker thematic land cover-induced
    backscatter differences. Additionally, comparison of backscatter from multiple
    satellites, modes, or tracks loses meaning.


    A Planetary Computer account is required to retrieve SAS tokens to read the RTC
    data. See the [documentation](http://planetarycomputer.microsoft.com/docs/concepts/sas/#when-an-account-is-needed)
    for more information.


    ### Methodology


    The Sentinel-1 GRD product is converted to calibrated intensity using the conversion
    algorithm described in the ESA technical note ESA-EOPG-CSCOP-TN-0002, [Radiometric
    Calibration of S-1 Level-1 Products Generated by the S-1 IPF](https://ai4edatasetspublicassets.blob.core.windows.net/assets/pdfs/sentinel-1/S1-Radiometric-Calibration-V1.0.pdf).
    The flat earth calibration values for gamma correction (i.e. perpendicular to
    the radar line of sight) are extracted from the GRD metadata. The calibration
    coefficients are applied as a two-dimensional correction in range (by sample number)
    and azimuth (by time). All available polarizations are calibrated and written
    as separate layers of a single file. The calibrated SAR output is reprojected
    to nominal map orientation with north at the top and west to the left.


    The data is then radiometrically terrain corrected using PlanetDEM as the elevation
    source. The correction algorithm is nominally based upon D. Small, [“Flattening
    Gamma: Radiometric Terrain Correction for SAR Imagery”](https://ai4edatasetspublicassets.blob.core.windows.net/assets/pdfs/sentinel-1/2011_Flattening_Gamma.pdf),
    IEEE Transactions on Geoscience and Remote Sensing, Vol 49, No 8., August 2011,
    pp 3081-3093. For each image scan line, the digital elevation model is interpolated
    to determine the elevation corresponding to the position associated with the known
    near slant range distance and arc length for each input pixel. The elevations
    at the four corners of each pixel are estimated using bilinear resampling. The
    four elevations are divided into two triangular facets and reprojected onto the
    plane perpendicular to the radar line of sight to provide an estimate of the area
    illuminated by the radar for each earth flattened pixel. The uncalibrated sum
    at each earth flattened pixel is normalized by dividing by the flat earth surface
    area. The adjustment for gamma intensity is given by dividing the normalized result
    by the cosine of the incident angle. Pixels which are not illuminated by the radar
    due to the viewing geometry are flagged as shadow.


    Calibrated data is then orthorectified to the appropriate UTM projection. The
    orthorectified output maintains the original sample sizes (in range and azimuth)
    and was not shifted to any specific grid.


    RTC data is processed only for the Interferometric Wide Swath (IW) mode, which
    is the main acquisition mode over land and satisfies the majority of service requirements.

    '
  provider: Catalyst
  license: CC-BY-4.0
  metadata:
    stac: true
    stac_api: true
    connector_id: planetary-computer
    tags:
    - ESA
    - Copernicus
    - Sentinel
    - C-Band
    - SAR
    - RTC
    dataset:
      tier: 1
      thematic_group: Satellite Imagery
      format: cog
      crs: EPSG:4326
      temporal:
        range: 2014-10-10/..
        type: snapshot
        default_range: latest
      quality:
        coverage: global
      layout:
        type: tiled
        spatial:
          scheme: mgrs
      stac_collection_id: sentinel-1-rtc
      homepage: https://planetarycomputer.microsoft.com/api/stac/v1/collections/sentinel-1-rtc