Effect of Target Moisture on Laser Scanner Intensity

Kaasalainen, Sanna; Niittymäki, Henri; Krooks, Anssi; Koch, Katharina; Kaartinen, Harri; Vain, Ants; Hyyppä, Hannu

doi:10.1109/tgrs.2009.2036841

Cited by 46 publications

(28 citation statements)

References 30 publications

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“…To estimate the parameters of the Phong model, natural logarithms can be conducted on the two sides of Equation (12). Thus, Equation (12) can be written as: log e (K) + n· log e [cos(2θ)] = log e (M) (13) where e is the Euler's number and K = K 0 ·k s .…”

Section: Proposed Methodsmentioning

confidence: 99%

“…Intensity, which is insensitive to ambient light and shadowing [5], is initially used to improve point cloud separability. Apart from visualization purposes, intensity data can be used as a major or complementary data source in various studies, such as vegetation and forest investigation [6,7], road traffic marking identification [8,9], water content extraction [6,[10][11][12][13], metro tunnel inspection [10,14], and lithological differentiation [5,15,16].…”

Section: Introductionmentioning

confidence: 99%

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Specular Reflection Effects Elimination in Terrestrial Laser Scanning Intensity Data Using Phong Model

Tan

Cheng

2017

Remote Sensing

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Abstract:The intensity value recorded by terrestrial laser scanning (TLS) systems is significantly influenced by the incidence angle. The incidence angle effect is an object property, which is mainly related to target scattering properties, surface structures, and even some instrumental effects. Most existing models focus on diffuse reflections of rough surfaces and ignore specular reflections, despite that both reflections simultaneously exist in all natural surfaces. Due to the coincidence of the emitter and receiver in TLS, specular reflections can be ignored at large incidence angles. On the contrary, at small incidence angles, TLS detectors can receive a portion of specular reflections. The received specular reflections can trigger highlight phenomenon (hot-spot effects) in the intensity data of the scanned targets, particularly those with a relatively smooth or highly-reflective surface. In this study, a new method that takes diffuse and specular reflections, as well as the instrumental effects into consideration, is proposed to eliminate the specular reflection effects in TLS intensity data. Diffuse reflections and instrumental effects are modeled by a polynomial based on Lambertian reference targets, whereas specular reflections are modeled by the Phong model. The proposed method is tested and validated on different targets scanned by the Faro Focus 3D 120 terrestrial scanner. Results imply that the coefficient of variation of the intensity data from a homogeneous surface is reduced by approximately 38% when specular reflections are considered. Compared with existing methods, the proposed method exhibits good feasibility and high accuracy in eliminating the specular reflection effects for intensity image interpretation and 3D point cloud representation by intensity.

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Section: Proposed Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Specular Reflection Effects Elimination in Terrestrial Laser Scanning Intensity Data Using Phong Model

Tan

Cheng

2017

Remote Sensing

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“…Since laser scanners never measure exactly the same point twice (Hodge et al, 2009); the perimeter of these holes and the position of topographic edges will move between successive point clouds, even despite no movement of the instrument. The likelihood of generating similar point distributions between surveys is also influenced by surface reflectance characteristics, such as moisture and colour, and by surface relief (Clark and Robson, 2004;Bae et al, 2005;Lichti et al, 2007;Kaasalainen et al, 2008Kaasalainen et al, , 2010Pesci et al, 2008Pesci et al, , 2011Soudarissanane et al, 2011). Scan lines in most laser scanners result in non-uniformly distributed data, with heterogeneity often on a scale and orientation comparable to surface structure, leading to aliasing that is also inconsistent (Lichti and Jamtsho, 2006).…”

Section: Scanning From a Fixed Positionmentioning

confidence: 99%

Optimising 4-D surface change detection: an approach for capturing rockfall magnitude–frequency

et al. 2018

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Abstract. We present a monitoring technique tailored to analysing change from near-continuously collected, high-resolution 3-D data. Our aim is to fully characterise geomorphological change typified by an event magnitude-frequency relationship that adheres to an inverse power law or similar. While recent advances in monitoring have enabled changes in volume across more than 7 orders of magnitude to be captured, event frequency is commonly assumed to be interchangeable with the time-averaged event numbers between successive surveys. Where events coincide, or coalesce, or where the mechanisms driving change are not spatially independent, apparent event frequency must be partially determined by survey interval.The data reported have been obtained from a permanently installed terrestrial laser scanner, which permits an increased frequency of surveys. Surveying from a single position raises challenges, given the single viewpoint onto a complex surface and the need for computational efficiency associated with handling a large time series of 3-D data. A workflow is presented that optimises the detection of change by filtering and aligning scans to improve repeatability. An adaptation of the M3C2 algorithm is used to detect 3-D change to overcome data inconsistencies between scans. Individual rockfall geometries are then extracted and the associated volumetric errors modelled. The utility of this approach is demonstrated using a dataset of ∼ 9 × 10 3 surveys acquired at ∼ 1 h intervals over 10 months. The magnitude-frequency distribution of rockfall volumes generated is shown to be sensitive to monitoring frequency. Using a 1 h interval between surveys, rather than 30 days, the volume contribution from small (< 0.1 m 3 ) rockfalls increases from 67 to 98 % of the total, and the number of individual rockfalls observed increases by over 3 orders of magnitude. High-frequency monitoring therefore holds considerable implications for magnitude-frequency derivatives, such as hazard return intervals and erosion rates. As such, while high-frequency monitoring has potential to describe short-term controls on geomorphological change and more realistic magnitude-frequency relationships, the assessment of longer-term erosion rates may be more suited to less-frequent data collection with lower accumulative errors.

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“…The use of the intensity return associated with each 3D point has been relatively limited, with most projects being restricted to singular intensity wavelength analysis. As the intensity return can be affected by the target surface reflectance values, the incidence angle, distance to target and atmospheric conditions (Kaasalainen, 2010), analysis of such data quickly becomes a complex multi-faceted problem to solve. Instrument calibration factors in heavily, especially if meaningful and accurate results are to be produced (Höfle, 2007).…”

Section: Related Workmentioning

confidence: 99%

“…Hence, the trial highlights the different results that are caused by use of different wavelength scanners. Kaasalainen et al (2010) performed a detailed study of the effects of scanning targets with varying percentage levels of moisture saturation to determine the effect on the returning intensity values. It was found that when using a near-infrared TLS there was a significant decrease in the backscattered reflectance values, but it depended strongly on both the target material composition and the level of moisture content.…”

Section: Related Workmentioning

confidence: 99%

Multispectral Analysis of Indigenous Rock Art Using Terrestrial Laser Scanning

Skoog

Helmholz

Belton

2016

Int. Arch. Photogramm. Remote Sens. Spatial Inf. Sci.

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ABSTRACT:Multispectral analysis is a widely used technique in the photogrammetric and remote sensing industry. The use of Terrestrial Laser Scanning (TLS) in combination with imagery is becoming increasingly common, with its applications spreading to a wider range of fields. Both systems benefit from being a non-contact technique that can be used to accurately capture data regarding the target surface. Although multispectral analysis is actively performed within the spatial sciences field, its extent of application within an archaeological context has been limited. This study effectively aims to apply the multispectral techniques commonly used, to a remote Indigenous site that contains an extensive gallery of aging rock art. The ultimate goal for this research is the development of a systematic procedure that could be applied to numerous similar sites for the purpose of heritage preservation and research. The study consisted of extensive data capture of the rock art gallery using two different TLS systems and a digital SLR camera. The data was combined into a common 2D reference frame that allowed for standard image processing to be applied. An unsupervised k-means classifier was applied to the multiband images to detect the different types of rock art present. The result was unsatisfactory as the subsequent classification accuracy was relatively low. The procedure and technique does however show potential and further testing with different classification algorithms could possibly improve the result significantly.

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Effect of Target Moisture on Laser Scanner Intensity

Cited by 46 publications

References 30 publications

Specular Reflection Effects Elimination in Terrestrial Laser Scanning Intensity Data Using Phong Model

Specular Reflection Effects Elimination in Terrestrial Laser Scanning Intensity Data Using Phong Model

Optimising 4-D surface change detection: an approach for capturing rockfall magnitude–frequency

Multispectral Analysis of Indigenous Rock Art Using Terrestrial Laser Scanning

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