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Keelung, Taiwan

Chang H.-C.,LIDAR Technology Co. | Sung Q.-C.,Chien Hsin University of Science and Technology
35th Asian Conference on Remote Sensing 2014, ACRS 2014: Sensing for Reintegration of Societies | Year: 2014

The south-western part of the Western Foothills is located at the deformation front of Taiwan Orogen. As the southern section of the Western Foothills is a part of incipient collision zone, the Plio-Pleistocene Gutingkeng Mudstone crops out extensively. The terraces, meanders, badlands and mud volcanoes are the most distinct landscapes in the Gutingkeng mudstone area, and this area has been known to have high rates of erosion and drastic landform changes. This study used multi-temporal geomorphological data to analyze the landform changes in Gutingkeng mudstones, and to elaborate the denudation rate and erosion characteristics in the mudstone area. This study adopted the Digital Elevation Model generated from 1921's topographic map and 1980's Orthophoto Base Map to assess the denudation rate; and used the archived satellite images to analyze the erosion characteristics of the mudstone area; finally estimated the surface erosion rate of a reserved mud-volcano district measured by 3D ground-based laser scanner in a typhoon event. The results showed the erosion rate of the Gutingkeng mudstone is about 39 mm/yr in the last 60 years by subtracting the 1980's DEM from the 1921's; The bald mudstone area has extended at a rate of 2.5 km2/yr in the last 7 years estimated from satellite image analysis and encroaches on the vegetated lands in an outward and backward fashion. Using a 3D ground-based Laser Scanner to monitor the mud volcanoes changes, the results showed a high erosion rate in the Gutingkeng mudstone of at least 9.8 cm yearly, especially when attacked by the typhoons or/and torrential rainfalls. Source

Chen Y.-C.,National Cheng Kung University | Chen C.-Y.,National Cheng Kung University | Matzarakis A.,Research Center Human Biometeorology | Liu J.-K.,LIDAR Technology Co. | Lin T.-P.,National Cheng Kung University
Atmospheric Research | Year: 2016

Assessment of outdoor thermal comfort is becoming increasingly important due to the urban heat island effect, which strongly affects the urban thermal environment. The mean radiant temperature (Tmrt) quantifies the effect of the radiation environment on humans, but it can only be estimated based on influencing parameters and factors. Knowledge of Tmrt is important for quantifying the heat load on human beings, especially during heat waves. This study estimates Tmrt using several methods, which are based on climatic data from a traditional weather station, microscale ground surface measurements, land surface temperature (LST) and light detection and ranging (LIDAR) data measured using airborne devices. Analytical results reveal that the best means of estimating Tmrt combines information about LST and surface elevation information with meteorological data from the closest weather station. The application in this method can eliminate the inconvenience of executing a wide range ground surface measurement, the insufficient resolution of satellite data and the incomplete data of current urban built environments. This method can be used to map a whole city to identify hot spots, and can be contributed to understanding human biometeorological conditions quickly and accurately. © 2016 Elsevier B.V. Source

Tseng C.-M.,Chang Jung Christian University | Lin C.-W.,National Cheng Kung University | Stark C.P.,Lamont Doherty Earth Observatory | Liu J.-K.,LIDAR Technology Co. | And 2 more authors.
Earth Surface Processes and Landforms | Year: 2013

Sediments produced by landslides are crucial in the sediment yield of a catchment, debris flow forecasting, and related hazard assessment. On a regional scale, however, it is difficult and time consuming to measure the volumes of such sediment. This paper uses a LiDAR-derived digital terrain model (DTM) taken in 2005 and 2010 (at 2m resolution) to accurately obtain landslide-induced sediment volumes that resulted from a single catastrophic typhoon event in a heavily forested mountainous area of Taiwan. The landslides induced by Typhoon Morakot are mapped by comparison of 25cm resolution aerial photographs taken before and after the typhoon in an 83.6km2 study area. Each landslide volume is calculated by subtraction of the 2005 DTM from the 2010 DTM, and the scaling relationship between landslide area and its volume are further regressed. The relationship between volume and area are also determined for all the disturbed areas (VL=0.452AL 1.242) and for the crown areas of the landslides (VL=2.510AL 1.206). The uncertainty in estimated volume caused by use of the LiDAR DTMs is discussed, and the error in absolute volume estimation for landslides with an area >105m2 is within 20%. The volume-area relationship obtained in this study is also validated in 11 small to medium-sized catchments located outside the study area, and there is good agreement between the calculation from DTMs and the regression formula. By comparison of debris volumes estimated in this study with previous work, it is found that a wider volume variation exists that is directly proportional to the landslide area, especially under a higher scaling exponent. Copyright © 2013 John Wiley & Sons, Ltd. Source

Chiu C.-L.,Central Geological Survey | Fei L.-Y.,Central Geological Survey | Liu J.-K.,LIDAR Technology Co. | Wu M.-C.,National Cheng Kung University
International Geoscience and Remote Sensing Symposium (IGARSS) | Year: 2015

For the purposes of geohazard study, a national airborne LiDAR mapping program spanning 2010 to 2015 was launched with the aim of simultaneously capturing the territory (36,000km2) by airborne LiDAR and digital imagery. The results include very detailed digital elevation models (DEM) and digital surface models (DSM) of 1m grid and digital aerial photograph of 50 cm grid, as well as an inventory of the geological disastrous features with the acquired LiDAR data and images. In total, 400 deep-seated landslides are obtained in a preliminary interpretation. In this paper, an example in Chasan Tribal Settlement of the large-scaled landslides is selected for validation to further inspected with other geological investigation means. The results of this paper demonstrate the merit of the national airborne LiDAR survey and the effectiveness of simple manual interpretation approach for a census of deep-seated landslides with LiDAR-derived images of various types of enhancement such as shaded relief. © 2015 IEEE. Source

Chang K.-T.,Minghsin University of Science and Technology | Liu J.-K.,LIDAR Technology Co. | Wang C.-I.,Minghsin University of Science and Technology
Journal of Marine Science and Technology (Taiwan) | Year: 2012

Landslides are natural phenomena for the dynamic balance of the earth's surface. Because of frequent occurrences of typhoons and earthquakes in Taiwan, mass movements are common threats to people's lives. In this paper, the interpretation of knowledge is quantified as recognition criteria. Multisource high-resolution data, for example, a SPOT satellite image, 20 m × 20 m Digital Terrain Model (DTM) reduced from Light Detection And Ranging (LiDAR) data, and aerial orthophotos were used to construct the feature space for landslide analysis. Landslides were recognized by an objectoriented method combining edge-based segmentation and a Supported Vector Machine (SVM) method. The classification results are evaluated in comparison with those by manual interpretation. Two cases from northern and central Taiwan are tested. Both cases show that the object-based SVM method is better than a pixel-based method in classification accuracy. The commission error of the proposed method is also smaller than that of the pixel-based method. Moreover, except for the spectral features, the slope and Object Height Model (OHM) characteristics are also important factors for improving landslide classification accuracy. Further study is required for assessing the mixed pixel effect when the resolution is as large as 20 m and for characterizing the effects of sampling rates or scaling caused by changes in resolution. Source

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