LiDAR Data Quality Standards, Certification Discussed at LiDAR Forum Session
The International Lidar Mapping Forum (ILMF) kicked off this morning with a session specifically created to discuss "hot topics" from the American Society for Photogrammetry and Remote Sensing (ASPRS). Lewis Graham, president of GeoCue moderated the session that included:
- Dr. Michael Hauck, executive director of the ASPRS who provided background on the evolution of LiDAR technology
- Dr. David Maune (pictured at right) from Dewberry that discussed the ASPRS accuracy standards for digital geospatial data
- Ajit Sampath, a USGS contractor, talked about developing internal data quality metrics for LiDAR and the ongoing research project between the ASPRS and the U.S. Geological Survey.
Hauck raised the question of whether the ASPRS should consider adopting certification requirements for those professionals using LiDAR technology similar to that of GIS certification. Many were in favor while some considered that may be within the bounds of some of the existing certifications that the ASPRS already offers such as a certified photogrammetrist. The argument is that LiDAR, like any other data type utilizing reflected light, visible or otherwise, is already within the bounds of ASPRS certification.
Maune discussed in great detail both the horizontal and vertical accuracy standards (see the ASPRS website for specifics on these standards). However, Maune drew particular attention to the Class IV Vertical Accuracy standards that provide the foundation for the USGS's 3D elevation program (3DEP). From his presentation:
Class IV elevation data equivalent to 1-foot contour accuracy approximates Quality Level 2 (QL2) from the National Enhanced Elevation Assessment (NEEA) when using airborne lidar point density of 2 points per square meter … the NEEA's Quality Level 1 (QL1) has the same vertical accuracy as QL2 but with point density of 8 points per square meter (Class III density). QL2 lidar specification are found in the USGS Lidar Base Specifications Version 1.1.
Sampath noted that Lidar data have become the primary means of 3D mapping. He said that quality standards transform lidar point cloud from a pretty visualization to metric data. However, quality control and assurance processes are not consistently applied. Pointedly he said that with large projects such as 3DEP, consistent geometric quality assessment methods for procurement purposes are needed. Currently, the USGS and ASPRS are researching a data quality metrics (DQM) test plan with the objective of correctly quantifying the quality of data for procurement and scientific applications.
Sampath noted that quality of calibration manifests most clearly in overlapping regions of adjacent swaths. The importance of well calibrated instrument cannot be overstated and that a consistently quantifiable process to check quality is needed.
Currently, Sampath said that prototype research software that implements DQMs has been developed and are being tested. ASPRS guidelines on geometric quality of lidar data will incorporate the results of the analysis. It is expected that this USGS led research will result in an across-the board improvement in the quality of lidar data and that new DQMs will provide the geospatial community with the capability to procure.