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Spectral response profiles

A target profile records the bands a dataset represents, including the response method, source and version. Frozen model artifacts contain the complete profile; workers never download or update response curves at inference time.

Custom profile format​

Wavelengths and bandwidths are always in nanometres. Bands must be ordered by increasing center wavelength and have unique names. This Gaussian example has one target band:

{
  "schema_version": 1,
  "algorithm": "band-integral-v1",
  "id": "laboratory-target",
  "name": "Laboratory target",
  "version": "1",
  "method": "gaussian",
  "source": "Laboratory calibration, revision 1",
  "bands": [
    {"name": "Band 1", "center_nm": 500, "fwhm_nm": 20}
  ]
}

For measured curves, set method to sensor_response and provide response_wavelengths_nm and response arrays for each band. The arrays must have equal length, increasing finite positive wavelengths, nonnegative finite responses, positive response area and zero endpoints. The center must be inside the response interval. Supply measured FWHM where available.

interpolation profiles align centers with linear interpolation. Existing center-only dataset settings also retain their other interpolation methods.

Meaning and limits​

The operator computes a normalized response-weighted average of a piecewise linear source spectrum. Integration accounts for unequal source wavelength spacing. Gaussian approximations use supplied target FWHM and a response support of four standard deviations on either side of the center. A maximum source gap may tighten the sampling requirement; it cannot enable spectral sharpening.

Per-image FWHM can identify matching Gaussian bands and avoid convolving them again. Measured curves require explicit response identity to do the same: an ENVI header can declare spectral response fingerprint equal to the profile fingerprint supplied by the catalog. Generic sensor names and equal centers are insufficient. The full identity must describe the actual instrument and selected bands, rather than a desired output.

Source band values are treated as spectral samples. Finite source bandwidths can limit accuracy even when their sampling is dense; broad source bands cannot recover finer features. This matches spectral bands, not spatial resolution, noise, atmospheric conditions or radiometric calibration. Compare compatible physical quantities and processing levels.

Response-profile models currently require batch inference. Live inference rejects them because the live hardware path has no qualified response operator. Models without a response profile retain their existing live behavior.

PCA fitting and its analysis scores use the same resampled measurements. The current generator stores PCA analysis artifacts separately and retains spectral band values in TFRecords.

Bundled calibration sources​

The catalog preserves published numerical samples. Negative measurement noise in USGS curves is clipped to zero. Nonzero end samples receive a zero endpoint one source grid step outside the supplied range. Profile centers are response centroids; these may differ from nominal rounded product band centers. Exact band names and order are retained, including separate panchromatic and cirrus bands. Select the bands present in the intended product.

Production sensor coverage​

A read-only survey on 2026-10-13 inspected the active sensor inventory and one representative available primary header per sensor label. Thirty representative calibrations had explicit recognized units, unique wavelength centers and one positive FWHM per band. Automated tests exercise those arrays through dataset and inference operators, including WorldView-2/3, Hyperion, EnMAP, Tanager, Wyvern, PlanetScope, Sentinel-2, Landsat-9, AVIRIS, HyMap, Pixxel, OSK GHOSt, Specim FX10/FX17/GX17 and other industrial/airborne configurations.

Some production headers lack bandwidths or units, contain mismatched bandwidth counts, or have no accessible header. Those sensors can supply explicit custom calibration; a sensor name alone does not qualify a fixed response profile. The sampled fixtures establish these particular calibrations, not every instrument, product variant or acquisition bearing that name.