Level 1C absolute geometric disparity metrics

This metadata file summarises the comparison between a specific band of processed image and a reference image.

Tiepoints are collected that correspond between the reference and processed images. The distances between these corresponding tiepoints are measured.

note

The tiepoints collected during the quality assessment are collected independently of the tiepoints collected during processing.

Sample file

Sample: LANDSAT-9_OLI_20220804T083603_20220804T083634_L1C_R1C1_GVER_ABS.json

Property details

This section contains explanations on specific properties of the absolute geometric disparity metrics file. All the properties 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 absolute geometric disparity metadata file contains a measurements section. This section is an array of measurements taken against a reference dataset.

Property	Description
id	The band-ID being measured
refBand	A formatted string describing the reference band used for the measurement (example, "Band 4 (red)")
refResolution	An array with across- and along-track resolutions for the reference band
refSpacecraft	The name of the reference spacecraft being used (example, "Sentinel-2")
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: absolute geometric disparity metrics

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

• measurements (array): A list of disparity metrics grouped by individual bands.
  • Items (object)
    • coordsLonLat (array): The (longitude, latitude) coordinates of the evaluated tie-points.
      • Items (array)
        • Items (number, format: double)
    • coverage (integer, format: int32): Total percentange of the scene that could be evaluated by the tie-points.
    • disparitiesXYInMeters (array): A list of (x,y) disparities of the evaluated tie-points (in meters).
      • Items (array)
        • Items (number, format: double)
    • id (string)
    • imageName (string): An illustration of the quality of all the tie-points evaluated on the image.
    • refBand (string): The band ID of the reference image being used during comparison.
    • refResolution (array): The resolution of the reference image used during comparison.
      • Items (number, format: double)
    • refSpacecraft (string): The Spacecraft ID of the associated reference image.
• pixelColorMappings (string): Mappings used to quantify disparities in color ranges (only for display purposes).