Absolute Radiometric Calibration of ALS Intensity Data: Effects on Accuracy and Target Classification

Kaasalainen, Sanna; Pyysalo, Ulla; Krooks, Anssi; Vain, Ants; Kukko, Antero; Hyyppä, Juha; Kaasalainen, M.

doi:10.3390/s111110586

Cited by 39 publications

(29 citation statements)

References 32 publications

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“…Further processing was carried out at the FGI. A range correction was applied to the intensity information to make relative radiometric calibration (Ahokas et al, 2006;Kaasalainen et al, 2011). As expected, our preliminary analyses with uncorrected data showed that intensity values were highest in the middle of a flight line and decreased as the distance from the scanner increased.…”

Section: Multispectral Als Datamentioning

confidence: 56%

Multispectral Airborne Laser Scanning for Automated Map Updating

Matikainen¹,

Hyyppä²,

Litkey³

2016

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

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ABSTRACT:During the last 20 years, airborne laser scanning (ALS), often combined with multispectral information from aerial images, has shown its high feasibility for automated mapping processes. Recently, the first multispectral airborne laser scanners have been launched, and multispectral information is for the first time directly available for 3D ALS point clouds. This article discusses the potential of this new single-sensor technology in map updating, especially in automated object detection and change detection. For our study, Optech Titan multispectral ALS data over a suburban area in Finland were acquired. Results from a random forests analysis suggest that the multispectral intensity information is useful for land cover classification, also when considering ground surface objects and classes, such as roads. An out-of-bag estimate for classification error was about 3% for separating classes asphalt, gravel, rocky areas and low vegetation from each other. For buildings and trees, it was under 1%. According to feature importance analyses, multispectral features based on several channels were more useful that those based on one channel. Automatic change detection utilizing the new multispectral ALS data, an old digital surface model (DSM) and old building vectors was also demonstrated. Overall, our first analyses suggest that the new data are very promising for further increasing the automation level in mapping. The multispectral ALS technology is independent of external illumination conditions, and intensity images produced from the data do not include shadows. These are significant advantages when the development of automated classification and change detection procedures is considered.

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Section: Multispectral Als Datamentioning

confidence: 56%

Multispectral Airborne Laser Scanning for Automated Map Updating

Matikainen¹,

Hyyppä²,

Litkey³

2016

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

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“…Ya que la zona de estudio es extensa y el terreno muestra una alta variabilidad en cuanto a pendientes y altitudes, los valores de intensidad se normalizaron en función de un rango estándar, con el fin de eliminar la dependencia de los valores de intensidad con respecto a la altura de vuelo (García et al 2010) y al ángulo de incidencia (Kaasalainen et al 2011). Así, la intensidad normalizada (I') se obtuvo mediante la multiplicación del valor bruto de la intensidad (I) por el cociente entre el rango de cada retorno (rg, m) y el rango estándar (rg s , m) (en este caso 1.000 m) y por el inverso del coseno del ángulo de incidencia del rayo láser (α, radianes).…”

Section: Normalización De La Intensidad De Los Datos Lidarunclassified

Estimación de las existencias maderables de Pinus radiata a escala provincial utilizando datos LiDAR de baja resolución

et al. 2017

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SUMMARYIn this study, the stand volume (V, m 3 ha -1 ) of Pinus radiata plantations of the province of Lugo (NW of Spain) was estimated using LiDAR-derived metrics from the low-density countrywide LiDAR dataset provided by the Spanish National Aerial Photography Program. The estimate was based on a oriented field inventory design to improve the fit of the model and on a inferential method based on the variability of the model parameter estimation and the variability of the LiDAR variable in the target population, which allowed to estimate the population mean and the standard error of V. A total of 25 permanent field inventory plots −that represent adequately the existing range of ages, stand densities and sites of the species in the province− were measured in order to fit the empirical relationship between field-measured V and LiDAR-derived metrics, using linear and (multiplicative) power function models. Regression analysis indicated a strong relationship between V and the 70 percentile of the LiDAR normalized height distribution (h 70 ) using a power function model (R 2 = 0.899; RMSE = 63.4 m 3 ha -1 ). The selected model was applied to all timber and high-pole development stands of P. radiata with coverage of this species superior to the 60 % according to the Spanish National Forest Map. Finally, a spatial-explicit map that describes V was produced. In 2009, the estimated mean population for V was 166.3 m 3 ha -1 with a relative sampling error of 13.9 %. This methodology will allow generating thematic maps every six years (temporal resolution scheduled for the PNOA LiDAR flights).Key words: Airborne Laser Scanning (ALS), Forest Inventory (FI), Remote Sensing (RS), estimators, regression models. RESUMENSe estimó el volumen de madera de rodal (V, m 3 ha -1 ) de Pinus radiata en la provincia de Lugo (NO España) a partir de métricas de datos LiDAR de baja resolución del PNOA (Plan Nacional de Ortofotografía de España). La estimación se basó en un diseño de muestreo orientado para mejorar el ajuste del modelo y en un método inferencial basado en la variabilidad de la estimación de los parámetros del modelo y en la variabilidad de la variable LiDAR en la población objetivo, lo que permitió estimar la media poblacional y el error en la estimación de V. Se usaron 25 parcelas permanentes, que cubren el rango existente de calidad, edad y densidad en los rodales de la especie en la provincia y se ajustaron modelos lineales y potenciales. El mejor resultado se obtuvo con un modelo potencial entre V y el percentil 70 de la altura normalizada (h 70 ) (R 2 = 0,899; REMC = 63,4 m 3 ha -1 ). Dicho modelo se aplicó a todas las teselas de P. radiata de la provincia de Lugo con estados de desarrollo de latizal y fustal y con ocupación de la especie superior al 60 % según el Mapa Forestal de España. Luego, se elaboró un mapa espacialmente explícito que describe V a escala provincial. En 2009 la media poblacional estimada para V fue de 166,3 m 3 ha -1 , con un error relativo de muestreo del 13,9 %. Esta metodología permitirá gener...

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“…Although Equation (4) is a simplified mathematical law and the light scattering behaviors of most natural surfaces are not Lambertian, many studies have reported that incidence angle dependence for many surfaces approximately follows the cosθ relation [4,7,8,[15][16][17][18]. However, the accuracy of the correction of the incidence angle effect can be further improved.…”

Section: Existing Correction Methods For Distance and Incidence Anglementioning

confidence: 99%

“…For relative correction [17], only a value related to the reflectance should be acquired so that f 1 pρ s q can be arbitrarily defined; this scenario means that the corrected intensity value calculated by Equation (23) is relative but comparable. Selecting different reference targets leads to different relative correction results.…”

Section: Proposed Model For Intensity Correctionmentioning

confidence: 99%

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Correction of Incidence Angle and Distance Effects on TLS Intensity Data Based on Reference Targets

Tan

Cheng

2016

Remote Sensing

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Abstract:The original intensity value recorded by terrestrial laser scanners is influenced by multiple variables, among which incidence angle and distance play a crucial and dominant role. Further studies on incidence angle and distance effects are required to improve the accuracy of currently available methods and to implement these methods in practical applications. In this study, the effects of incidence angle and distance on intensity data of the Faro Focus 3D 120 terrestrial laser scanner are investigated. A new method is proposed to eliminate the incidence angle and distance effects. The proposed method is based on the linear interpolation of the intensity values of reference targets previously scanned at various incidence angles and distances. Compared with existing methods, a significant advantage of the proposed method is that estimating the specific function forms of incidence angle versus intensity and distance versus intensity is no longer necessary; these are canceled out when the scanned and reference targets are measured at the same incidence angle and distance. Results imply that the proposed method has high accuracy and simplicity in eliminating incidence angle and distance effects and can significantly reduce the intensity variations caused by these effects on homogeneous surfaces.

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Absolute Radiometric Calibration of ALS Intensity Data: Effects on Accuracy and Target Classification

Cited by 39 publications

References 32 publications

Multispectral Airborne Laser Scanning for Automated Map Updating

Multispectral Airborne Laser Scanning for Automated Map Updating

Estimación de las existencias maderables de Pinus radiata a escala provincial utilizando datos LiDAR de baja resolución

Correction of Incidence Angle and Distance Effects on TLS Intensity Data Based on Reference Targets

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