Hemispherical reflectance model for passive images in an outdoor environment

The intensity data recorded by terrestrial laser scanning systems are considered significant measures of the spectral property of scanned objects. These data can be used in an extensive range of object-based applications. However, the direct retrieval of reflectance from intensity information is infeasible because intensity data are influenced by multiple variables, particularly distance and incidence angle. This study proposes a new method to recover the absolute reflectance value of the scanned surface by eliminating the effects of distance and incidence angle. The Faro Focus 120 terrestrial scanner is utilized in the case study. Two sets of experiments are designed to estimate the parameters of the developed model by using Lambertian targets at different reflectance values. With the estimated parameters, the proposed method is applied to recover the reflectance values of natural surfaces. The deviation of the retrieved reflectance values of natural surfaces from the reflectance values measured by a spectrometer is approximately 2.64%. Results show that the proposed method exhibits high accuracy in retrieving reflectance values and can be utilized for actual mapping tasks and geological applications.

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Modeling hemispherical reflectance for natural surfaces based on terrestrial laser scanning backscattered intensity data

Tan

Cheng

2016

Opt. Express

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Independent of instrumental properties and scanning geometry, target reflectance is significantly important for terrestrial laser scanning (TLS) data processing and utilization, especially in multi-temporal and multi-sensor cases. In addition to the 3D topographic coordinates, TLS systems also record the backscattered intensity value of each point that provides additional information on the reflectance characteristics of the scanned surface. However, a number of confounding variables, particularly the distance and incidence angle, distort the ability of the original intensity to directly retrieve the target reflectance. This study proposes a new method to model the hemispherical reflectance of natural surfaces from the TLS intensity data by eliminating the effects of incidence angle and distance. The incidence angle effect is corrected by the Oren-Nayar reflectance model which takes individual surface roughness into account whereas the irregular distance effect is eliminated by reference targets without estimating the specific distance-intensity function. The Faro Focus^3D 120 terrestrial scanner is utilized in the case study. Six typical natural surfaces are chosen as the experimental objects. Results imply that the proposed method exhibits high accuracy in retrieving reflectance values. The deviation of the retrieved reflectance values from that measured by a spectrometer is approximately 4.29% and the root mean square error (RMSE) is approximately 0.0562.

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Hemispherical reflectance model for passive images in an outdoor environment

Cited by 4 publications

References 13 publications

Bidirectional reflection distribution function modeling (BRDF) for terahertz diffuse scattering analysis of dielectric rough targets

Bidirectional reflection distribution function modeling (BRDF) for terahertz diffuse scattering analysis of dielectric rough targets

Surface reflectance retrieval from the intensity data of a terrestrial laser scanner

Modeling hemispherical reflectance for natural surfaces based on terrestrial laser scanning backscattered intensity data

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