Radiometric Calibration of a Dual-Wavelength, Full-Waveform Terrestrial Lidar

Abstract

Radiometric calibration of the Dual-Wavelength Echidna® Lidar (DWEL), a full-waveform terrestrial laser scanner with two simultaneously-pulsing infrared lasers at 1064 nm and 1548 nm, provides accurate dual-wavelength apparent reflectance (ρapp), a physically-defined value that is related to the radiative and structural characteristics of scanned targets and independent of range and instrument optics and electronics. The errors of ρapp are 8.1% for 1064 nm and 6.4% for 1548 nm. A sensitivity analysis shows that ρapp error is dominated by range errors at near ranges, but by lidar intensity errors at far ranges. Our semi-empirical model for radiometric calibration combines a generalized logistic function to explicitly model telescopic effects due to defocusing of return signals at near range with a negative exponential function to model the fall-off of return intensity with range. Accurate values of ρapp from the radiometric calibration improve the quantification of vegetation structure, facilitate the comparison and coupling of lidar datasets from different instruments, campaigns or wavelengths and advance the utilization of bi- and multi-spectral information added to 3D scans by novel spectral lidars.

Observing ecosystems with lightweight, rapid‐scanning terrestrial lidar scanners

“…Therefore, independent calibration of instruments is recommended, utilizing objects with equivalent geometry and reflective properties to those found in the ecosystem to be sampled. Fortunately, pulse-level uncertainties can be robustly established with everimproving methods (Kaasalainen et al 2009;Li et al 2016).…”

“…; Li et al. ) and the SALford Advanced Canopy Analyzer (SALCA) (Danson et al. ), and commercially available instruments such as the Riegl VZ‐400 (Calders et al.…”

“…Capability is characterized by improvements in the attributes of individual lidar pulses, such as range, resolution and emitted wavelengths, increasing the maximum capabilities of an instrument. Contemporary archetypes include the research instruments, the Dual-Wavelength Echidna Lidar (DWEL) (Strahler et al 2008;Douglas et al 2012;Howe et al 2015;Li et al 2016) and the SALford Advanced Canopy Analyzer (SALCA) (Danson et al 2014), and commercially available instruments such as the Riegl VZ-400 . While some of these highly capable instruments allow for variable scanning settings to decrease resolution and increase scanning speed, small, practical terrestrial lidar instruments offer the means to augment and extend the extensive, high-caliber information acquired with more capable scanners.…”

Damage Detection for Historical Architectures Based on TLS Intensity Data

“…Compared with ALS data, only a few recent studies have focused on the TLS intensity correction. And its correction also faces more unique challenges than ALS data (Li et al, 2016). Many studies have found that the intensity data does not follow the LiDAR equation in the near range and different TLS systems may result in different intensity-range relations (Kaasalainen et al, 2011;Fang et al, 2014;.…”

Evaluation of the Range Accuracy and the Radiometric Calibration of Multiple Terrestrial Laser Scanning Instruments for Data Interoperability

“…However, using intensity information from a single wavelength scanner limits this separation because the received intensity is a function of the spectral reflectance properties of the canopy constituents, the area of the beam that is intercepted, and the local angle of incidence [37]. The dual-wavelength scanners DWEL and SALCA try to overcome the limitations of a single-wavelength scanner by taking the spectral ratio of the two laser wavelengths at approximately 1064 and 1550 nm [37], [38].…”