Automated measurements of terrain reflection and height variations using an airborne infrared laser system

Schreier, H.; Lougheed, J.; Tucker, C.; Leckie, Donald G.

doi:10.1080/01431168508948427

Cited by 61 publications

(35 citation statements)

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“…For pulse lasers, intensity often represents the peak amplitude of the returned pulse. Although it was demonstrated already in the mid 1980s that intensity from airborne lasers could assist in classification of individual trees into conifers and broadleaves [19], further development has been hampered by lack of methods for radiometric calibration of the intensity [20]. Lately, there is evidence of various intensity variables from ALS providing useful information for tree species classification [21][22][23][24][25][26][27].…”

Section: Introductionmentioning

confidence: 99%

Discrimination between Ground Vegetation and Small Pioneer Trees in the Boreal-Alpine Ecotone Using Intensity Metrics Derived from Airborne Laser Scanner Data

Næsset¹

2016

Remote Sensing

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Abstract:It has been shown that height measurements obtained by airborne laser scanning (ALS) with high point density (>7-8 m´2) can be used to detect small trees in the alpine tree line-an ecotone sensitive to climate change. Because the height measurements do not discriminate between trees and other convex structures with positive height values, this study aimed at assessing the contribution of ALS backscatter intensity to classification of trees and non-trees. The study took place in a boreal-alpine ecotone in southeastern Norway and was based on 500 precisely georeferenced small trees and non-tree objects for which ALS height and intensity were derived from four different ALS acquisitions, representing different sensors, pulse repetition frequencies (PRF), and flying altitudes. The sensors operated at 1064 nm. Based on logistic regression modeling, it was found that classification into three different tree species ((1) spruce; (2) pine; and (3) birch)) and two different non-tree object types (objects with: (1) vegetated surface; and (2) rock) was significantly better (p < 0.001-0.05) than a classification based on models with trees and non-trees as binary response. The cause of the improved classification is mainly diverse reflectivity properties of non-tree objects. No effect of sensor, PRF, and flying altitude was found (p > 0.05). Finally, it was revealed that in a direct comparison of the contribution of intensity backscatter to improve classification models of trees and non-trees beyond what could be obtained by using the ALS height information only, the contribution of intensity turned out to be far from significant (p > 0.05). In conclusion, ALS backscatter intensity seems to be of little help in classification of small trees and non-trees in the boreal-alpine ecotone even when a more detailed discrimination on different species and different non-tree structures is applied.

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Section: Introductionmentioning

confidence: 99%

Discrimination between Ground Vegetation and Small Pioneer Trees in the Boreal-Alpine Ecotone Using Intensity Metrics Derived from Airborne Laser Scanner Data

Næsset¹

2016

Remote Sensing

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“…Airborne laser surveys have been used to measure vegetation properties (Schreier et al 1985, Nelson et al 1988, Ritchie et ai 1992, 1993, erosion and stream features Jackson 1989, Ritchie et al 1993 b), topography (Krabill et al 1984), and aerodynamic roughness Ritchie 1992, 1994). Surface features of the Earth and other planets have been measured from lasers on satellites (Bufton 1989, Seshamani 1993).…”

Section: Introductionmentioning

confidence: 99%

Measurements of land surface features using an airborne laser altimeter: the HAPEX-Sahel experiment

Ritchie

Menenti

Weltz

1996

International Journal of Remote Sensing

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Abstract. An airborne laser profiling altimeter was used to measure surface features and properties of the landscape during the HAPEX-Sahel Experiment in Niger, Africa in September 1992. The laser altimeter makes 4000 measurements per second with a vertical resolution of 5 cm. Airborne laser and detailed field measurements of vegetation heights had similar average heights and frequency distribution. Laser transects were used to estimate land surface topography, gully and channel morphology, and vegetation properties (height, cover and distribu tion). Land surface changes related to soil erosion and channel development were measured. For 1 km laser transects over tiger bush communities, the maximum vegetation height was between 4-5 and 6-5m, with an average height of 21m. Distances between the centre of rows of tiger bush vegetation averaged 100 m. For two laser transects, ground cover for tiger bush was estimated to be 22-5 and 30-1 per cent for vegetation greater than 0-5m tall and 190 and 25-8 per cent for vegetation greater than 10m tall. These values are similar to published values for tiger bush. Vegetation cover for 14 and 18 km transects was estimated to be 4 per cent for vegetation greater than 0-5 m tall. These cover values agree within 1-2 per cent with published data for short transects (<100m) for the area. The laser altimeter provided quick and accurate measurements for evaluating changes in land surface features. Such information provides a basis for understanding land degradation and a basis for management plans to rehabilitate the landscape.

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“…The amount of intercepted laser energy by foliage is correlated to the well-known indices related to leaf area (e.g., leaf area index, LAI) which is, in turn, related to stem diameter by different allometric relationships [47,48], as was also tested on large footprint FW LiDAR in [49]. Intensity was also found to give a valid contribution to vegetation cover classification in [50] due to the above reasons. These points contribute to explaining the positive correlation between the total return intensity and the measured AGB and BA values.…”

Section: Discussionmentioning

confidence: 99%

Small Footprint Full-Waveform Metrics Contribution to the Prediction of Biomass in Tropical Forests

et al. 2014

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Abstract:We tested metrics from full-waveform (FW) LiDAR (light detection and ranging) as predictors for forest basal area (BA) and aboveground biomass (AGB), in a tropical moist forest. Three levels of metrics are tested: (i) peak-level, based on each return echo; (ii) pulse-level, based on the whole return signal from each emitted pulse; and (iii) plot-level, simulating a large footprint LiDAR dataset. Several of the tested metrics have significant correlation, with two predictors, found by stepwise regression, in particular: median distribution of the height above ground (nZ median ) and fifth percentile of total pulse return intensity (i_tot 5th ). The former contained the most information and explained 58% and 62% of the variance in AGB and BA values; stepwise regression left us with two and four predictors, respectively, explaining 65% and 79% of the variance. For BA, the predictors were standard deviation, median and fifth percentile of total return pulse intensity (i_tot stdDev , i_tot median and i_tot 5th ) and nZ median , whereas for AGB, only the last two were used. The plot-based metric showed that the median height of echo count (HOMTC) performs best, with very similar results as nZ median , as expected. Cross-validation OPEN ACCESSRemote Sens. 2014, 6 9577 allowed the analysis of residuals and model robustness. We discuss our results considering our specific case scenario of a complex forest structure with a high degree of variability in terms of biomass.

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Automated measurements of terrain reflection and height variations using an airborne infrared laser system

Cited by 61 publications

References 1 publication

Discrimination between Ground Vegetation and Small Pioneer Trees in the Boreal-Alpine Ecotone Using Intensity Metrics Derived from Airborne Laser Scanner Data

Discrimination between Ground Vegetation and Small Pioneer Trees in the Boreal-Alpine Ecotone Using Intensity Metrics Derived from Airborne Laser Scanner Data

Measurements of land surface features using an airborne laser altimeter: the HAPEX-Sahel experiment

Small Footprint Full-Waveform Metrics Contribution to the Prediction of Biomass in Tropical Forests

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