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Level 1C relative geometric disparity metrics

Introduction​

This metadata file summarises the comparison between the different bands of an image. Tiepoints are collected for both bands.

Tiepoints are collected between different combination of bands of an image. The distances between these corresponding tiepoints are measured.

note

These tiepoints are independent of the tiepoints collected to process the image

The relative geometric verification metadata file is similar to the absolute geometric verification metadata file. However, the relative geometric verification metadata file contains measurements between the band combinations that were measured.

Sample file​

Sample: LANDSAT-9_OLI_20220804T083603_20220804T083634_L1C_R1C1_GVER_REL.json

Property details​

This section contains explanations on specific properties of the relative geometric disparity metrics file. All the properties that have been expanded on are listed in a structured manner under the Reference section.

Pixel colour mappings​

This section describes the pixelColorMappings property. This provides a legend to quantify disparities in colour ranges. This legend is used for the thumbnail referenced in imageName.

Measurements​

Each relative geometric disparity metadata file contains a measurements section. This section is an array of measurements taken between two bands, and contains:

  • from: The name of the spectral band from where the disparity is measured
  • to: The name of the spectral band to where the disparity is measured
  • imageName: The filename of the preview image being generated containing a visual representation of the results of the geometric verification
  • disparitiesXYInMeters: A 2-dimensional array containing a set of disparity measurements (see below)
  • coordLonLat: A 2-dimensional array containing the coordinates of each disparity measurements (see below)
  • coverage: A percentage (out of 100) showing how much of the scene is covered by the geometric verification results

The combination of disparitiesXYInMeters and coordLonLat can be used to generate a map of each disparity point. The coordinates, in the sequence [longitude, latitude] denotes where the measurement was taken. The disparities is expressed in meters as the distance away from the coordinate point in the sequence [longitude, latitude].

Reference: relative geometric disparity metrics​

The following reference describes the content of the relative geometric disparity metrics file.

  • measurements (array): A list of disparity metrics grouped by individual bands.
    • Items (object)
      • coordsLatLon (array): The (longitude, latitude) coordinates of the evaluated tie-points.
        • Items (array)
          • Items (number, format: double)
      • disparitiesXYInMeters (array): A list of (x,y) disparities of the evaluated tie-points (in meters).
        • Items (array)
          • Items (number, format: double)
      • from (string): The band ID of the source used during comparison.
      • imageName (string): An illustration of the quality of all the tie-points evaluated on the image.
      • to (string): The band ID of the target used during comparison.
  • pixelColorMappings (string): Mappings used to quantify disparities in color ranges (only for display purposes).