Resolved: NEON AOP Lidar Data Quality Issues Due to Mis-Classified Atmospheric Noise

The AOP lidar noise data quality issues first described in the 29 September 2022 Lidar Data Quality Notification, and updated in the subsequent 13 January 2023 Notification have been resolved across all impacted sites for the lidar and camera data products. Data provided in the 2026 Data Release reflect these quality updates.

Summary: Data collected in hazy or cloudy atmospheric conditions, especially at higher pulse-repetition-frequencies (PRFs) or power settings, have in some cases produced dense clusters of noisy lidar returns, which were not always filtered out as part of the standard noise-filtering routines. This issue affected not only the Level 1 Lidar Classified Point Cloud data product, but also downstream Level 3 Lidar raster data products (CHM, DTM/DSM, and Slope/Aspect) as well as the products derived from Camera and Spectrometer sensors, which rely on the Lidar DEM for orthorectification. In most cases the mis-classified noise was isolated to small portions of each site. NEON scientists have implemented improved algorithms for identifying and filtering out the dense and mis-classified noise, and in some cases have manually removed the noisy regions. We note that this may result in small data gaps for some sites.  All lidar and camera data products affected by this issue have now been updated. The spectrometer data products will be updated when they are re-processed to apply the topographic and BRDF corrections.

Most of the sites and dates affected have already been updated and included in previous releases, but as of RELEASE-2026, all of the remaining NEON site-years that exhibited this dense and mis-classified noise issue (PUUM 2019-01, REDB 2019-05, UNDE 2019-06, UKFS 2019-05) have now been updated. For a summary of when the lidar and camera data products were updated for the sites and dates affected, please refer to Table 1 below. Please also refer to the AOP Lidar Data Quality Notification - Update for a complete summary of data products, sites and dates originally affected by this data quality issue.

Table 1: Sites and years where the noise-related data quality issue was identified, and Release tag where the data quality issue was resolved. Note that the older releases are now Tombstoned, but all of these data quality updates are included in the most recent Release (RELEASE-2026).

Updated data products:

• Discrete return LiDAR point cloud (DP1.30003.001)
• Ecosystem structure (Canopy Height Model; DP3.30015.001)
• Elevation - Lidar (DP3.30024.001)
• Slope and Aspect - Lidar (DP3.30025.001)
• High-resolution orthorectified camera imagery (DP1.30010.001)
• High-resolution orthorectified camera imagery mosaic (DP3.30010.001)

Note that NEON's more recently acquired lidar sensors (Teledyne Optech Galaxy Prime and Riegl VQ780 II-S) operate at much higher frequencies (see the NEON Lidar webpage for more details) so we have continued to see dense atmospheric noise arise when operating in sub-optimal atmospheric conditions in more recent data acquisitions. The science team has implemented improved QA processes to identify and resolve the issue before publishing, so we don't anticipate this issue to be present in the data moving forward. 

Data quality updates are an ongoing process, and we value input from the community. If you notice any quality issues in AOP data collected over other NEON sites or dates, please use NEON's Contact Us form to report the issue.