Structural mapping of rock walls imaged with a LiDAR mounted on an unmanned aircraft system

Structural mapping of rock walls to determine fracture orientation provides critical geological information in support of mining operations. A helicopter-style UAS (rotor diameter 2 m; take-off mass 35 kg; payload mass 11 kg) instrumented with a high-resolution LiDAR imaged a 75 m long and 10–15 m high series of four adjacent rock walls at the Canadian Wollastonite mine. A point cloud with a density of 484 point/m2 acquired at an angle of incidence of ∼41.7° from a flight altitude of 41.7 m above ground level was selected for structural mapping. The point cloud was first meshed using the Poisson surface reconstruction method and then remeshed to achieve an even element size distribution. Visualization of the remeshed Poisson mesh using a 360° hue–saturation–lightness colour wheel highlighted areas of higher fracture density, whereas visualization using a 180° colour wheel accentuated sliver-like geological features. Two joint sets were identified at 156/82 and 241/86 (strike/dip in degrees). A total of 18 virtual strike measurements and 13 virtual dip measurements were within 10% of manual compass measurements. This study demonstrated that the task of structural mapping of large rock walls can be automated by processing 3D images acquired with a LiDAR mounted on a UAS.

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Geomorphological evolution of landslides near an active normal fault in northern Taiwan, as revealed by lidar and unmanned aircraft system data

Natural Hazards and Earth System Science ◽

10.5194/nhess-18-709-2018 ◽

2018 ◽

Vol 18 (3) ◽

pp. 709-727 ◽

Cited By ~ 8

Author(s):

Kuo-Jen Chang ◽

Yu-Chang Chan ◽

Rou-Fei Chen ◽

Yu-Chung Hsieh

Keyword(s):

Remote Sensing ◽

Normal Fault ◽

Unmanned Aircraft ◽

Airborne Lidar ◽

Reconstruction Method ◽

Remote Sensing Techniques ◽

Aircraft System ◽

Geomorphological Evolution ◽

Northern Taiwan ◽

Landslide Morphology

Abstract. Several remote sensing techniques, namely traditional aerial photographs, an unmanned aircraft system (UAS), and airborne lidar, were used in this study to decipher the morphological features of obscure landslides in volcanic regions and how the observed features may be used for understanding landslide occurrence and potential hazard. A morphological reconstruction method was proposed to assess landslide morphology based on the dome-shaped topography of the volcanic edifice and the nature of its morphological evolution. Two large-scale landslides in the Tatun volcano group in northern Taiwan were targeted to more accurately characterize the landslide morphology through airborne lidar and UAS-derived digital terrain models and images. With the proposed reconstruction method, the depleted volume of the two landslides was estimated to be at least 820 ± 20  ×  106 m3. Normal faulting in the region likely played a role in triggering the two landslides, because there are extensive geological and historical records of an active normal fault in this region. The subsequent geomorphological evolution of the two landslides is thus inferred to account for the observed morphological and tectonic features that are indicative of resulting in large and life-threatening landslides, as characterized using the recent remote sensing techniques.

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Geomorphological evolution of landslides near an active normal fault in Northern Taiwan, as revealed by LiDAR and unmanned aircraft system data

10.5194/nhess-2017-227 ◽

2017 ◽

Author(s):

Kuo-Jen Chang ◽

Yu-Chang Chan ◽

Rou-Fei Chen ◽

Yu-Chung Hsieh

Keyword(s):

Remote Sensing ◽

Normal Fault ◽

Unmanned Aircraft ◽

Airborne Lidar ◽

Reconstruction Method ◽

Remote Sensing Techniques ◽

Aircraft System ◽

Geomorphological Evolution ◽

Northern Taiwan ◽

Landslide Morphology

Abstract. Several remote sensing techniques, namely traditional aerial photographs, an unmanned aircraft system (UAS), and airborne LiDAR, were used in this study to decipher the morphological features of obscure landslides in volcanic regions. A morphological reconstruction method was proposed to assess landslide morphology based on the dome-shaped topography of the volcanic edifice and the nature of its morphological evolution. Two large-scale landslides in the Tatun volcano group in Northern Taiwan were targeted to more accurately characterize the landslide morphology through airborne LiDAR and UAS-derived digital terrain models and images. With the proposed reconstruction method, the depleted volume of the two landslides was estimated to be at least 820 ± 20 × 106 m3, approximately six times higher than the reported largest landslide volume in Taiwan. Normal faulting in the region likely played a role in triggering the two landslides, because there are extensive geological and historical records of an active normal fault in this region. The subsequent geomorphological evolution of the two landslides is inferred to account for the observed morphological and tectonic features, as characterized using the remote sensing techniques.

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Evaluation of Incident Light Sensors on Unmanned Aircraft for Calculation of Spectral Reflectance

Remote Sensing ◽

10.3390/rs11222622 ◽

2019 ◽

Vol 11 (22) ◽

pp. 2622

Author(s):

E. Raymond Hunt ◽

Alan J. Stern

Keyword(s):

Near Infrared ◽

Incident Light ◽

Accurate Determination ◽

Ground Level ◽

Unmanned Aircraft ◽

Landsat 8 ◽

The Sun ◽

Area Index ◽

Flight Direction ◽

Aircraft System

Including incident light sensors (ILS) with multispectral sensors is an important development for agricultural remote sensing because spectral reflectances are necessary for accurate determination of plant biophysical variables such as leaf area index and leaf chlorophyll content. Effects of different aircraft flight conditions on accuracy of surface reflectances retrieved using an ILS are not known. The objectives of this study were to assess the effects of ILS orientation with respect to sun and aircraft altitude. A Tetracam Miniature Multiple Camera Array (Mini-MCA) was mounted on a fixed-wing unmanned aircraft system (UAS) with the ILS mounted on top of the aircraft’s fuselage. On two dates the aircraft flew over six 50-ha agricultural fields with center-pivot irrigation at three different altitudes (450, 650 and 1800 m above ground level (AGL)). Ground reflectances were estimated using atmospherically corrected Landsat 8 Operational Land Imager data acquired at or near the time of the aircraft overflights. Because the aircraft had a positive pitch during flight, the ILS pointed opposite to the flight direction. The first date had flight lines closely oriented towards and away from the sun. The second date had flight lines oriented perpendicularly to the solar azimuth. On the first date, red and near-infrared (NIR) reflectances were significantly higher when the ILS was oriented away from the sun, whereas ILS orientation had little effect on the second date. For both dates, red and near-infrared reflectances were significantly greater at 450 m compared to 1800 m. Both the effects of ILS orientation and flight altitude are correctable during image processing because the physical basis is well known.

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