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QA Panels & Metrics

Each processed NEON flight line generates a set of quality assurance (QA) artifacts designed to summarize reflectance distributions, masks, geometry, and harmonization decisions.

This page describes the QA PNG, QA PDF, and QA JSON outputs.

QA PNG

The QA PNG provides a quick visual summary of:

  • reflectance distributions for key wavelengths
  • spatial distribution of masks
  • before/after brightness comparison
  • BRDF correction diagnostics
  • wavelength alignment checks

A typical PNG includes panels for:

  1. reflectance histograms
  2. strip-based brightness summaries
  3. cloud/water/snow/invalid pixel frequencies
  4. wavelength metadata
  5. sensor-specific diagnostics

Use this for fast visual inspection.

QA PDF

The PDF includes:

  • all PNG content
  • multi-page extended diagnostics
  • tabulated statistics
  • optional per-band summaries
  • BRDF coefficient tables
  • brightness adjustment coefficients

This document serves as a flight-line-level audit record.

QA JSON

The JSON file contains machine-readable metrics including:

Reflectance metrics

  • min/max/median for each band
  • proportion of saturated or masked pixels
  • brightness differences across correction stages

Mask summary metrics

  • percent cloud
  • percent cloud shadow
  • percent snow
  • percent water
  • percent invalid

BRDF metrics

  • per-band BRDF coefficients
  • reconstruction error statistics

Sensor harmonization metrics

  • brightness coefficients (per band)
  • spectral alignment checks
  • per-band RMSE for regression-based harmonization (if applicable)

Geometry metadata

  • solar zenith/azimuth
  • view zenith/azimuth
  • DEM statistics

Interpreting QA results

Flags to watch for:

  • Reflectance values > 1.5 → possible BRDF or DEM issues
  • Large brightness shifts → check convolution stage
  • High invalid or shadow fraction → consider masking strategy
  • Noisy BRDF coefficients → unstable correction in low-SNR regions

Next steps