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Dou J.,University of Tokyo | Chang K.-T.,Minghsin University of Science and Technology | Chen S.,Guangzhou Institute of Geography | Yunus A.P.,University of Tokyo | And 3 more authors.
Remote Sensing | Year: 2015

This paper proposes an automatic method for detecting landslides by using an integrated approach comprising object-oriented image analysis (OOIA), a genetic algorithm (GA), and a case-based reasoning (CBR) technique. It consists of three main phases: (1) image processing and multi-image segmentation; (2) feature optimization; and (3) detecting landslides. The proposed approach was employed in a fast-growing urban region, the Pearl River Delta in South China. The results of detection were validated with the help of field surveys. The experimental results indicated that the proposed OOIA-GA-CBR (0.87) demonstrates higher classification performance than the stand-alone OOIA (0.75) method for detecting landslides. The area under curve (AUC) value was also higher than that of the simple OOIA, indicating the high efficiency of the proposed landslide detection approach. The case library created using the integrated model can be reused for time-independent analysis, thus rendering our approach superior in comparison to other traditional methods, such as the maximum likelihood classifier. The results of this study thus facilitate fast generation of accurate landslide inventory maps, which will eventually extend our understanding of the evolution of landscapes shaped by landslide processes. © 2015 by the authors; licensee MDPI, Basel, Switzerland.

Liu J.-K.,LiDAR Technology Co. | Chang K.-T.,Minghsin University of Science and Technology | Lin C.,National Chiayi University | Chang L.-C.,National Chiao Tung University
International Geoscience and Remote Sensing Symposium (IGARSS) | Year: 2015

Recently, some global-scale DEM products, such as GTOPO30, ETOPO1, SRTM and ASTER GDEM have been published for geoscience applications. The latest product, ALOS DEM was announced to be available for a global coverage in 2016. This study examined the performance of ALOS-DEM in describing accurate morphometric and volumetric measurement of land features. A comparison was made on basis of DEM and DSM data of airborne full-waveform LiDAR data. Results showed that ALOS DEM is more approximately in reality an ALOS DSM which reveals the ground envelop surface rather than the ground bare surface. The differences between ALOS DEM and LiDAR DSM are mainly from 0 to 2.75 m with a standard deviation of 1.58 m. The differences between ALOS DEM and LiDAR DEM give a bias of as large as 20m, mostly located at the areas with abrupt change of relief and mainly in the north-facing slopes. This is probably due to ALOS sensor's geometry in corresponding to its looking-direction. The stream networks derived from both ALOS DEM and LiDAR DEM are in good agreement. It is suggested that further studies on methods for assessing geomorphometric changes in landform structures should be developed and compared. © 2015 IEEE.

Chang K.T.,Sudan University of Science and Technology | Lin C.,National Chiayi University | Lin Y.C.,Chung Cheng Institute of Technology | Liu J.K.,LIDAR Technology Co.
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences - ISPRS Archives | Year: 2016

Forest canopy density and height are used as variables in a number of environmental applications, including the estimation of biomass, forest extent and condition, and biodiversity. The airborne Light Detection and Ranging (LiDAR) is very useful to estimate forest canopy parameters according to the generated canopy height models (CHMs). The purpose of this work is to introduce an algorithm to delineate crown parameters, e.g. tree height and crown radii based on the generated rasterized CHMs. And accuracy assessment for the extraction of volumetric parameters of a single tree is also performed via manual measurement using corresponding aerial photo pairs. A LiDAR dataset of a golf course acquired by Leica ALS70-HP is used in this study. Two algorithms, i.e. a traditional one with the subtraction of a digital elevation model (DEM) from a digital surface model (DSM), and a pit-free approach are conducted to generate the CHMs firstly. Then two algorithms, a multilevel morphological active-contour (MMAC) and a variable window filter (VWF), are implemented and used in this study for individual tree delineation. Finally, experimental results of two automatic estimation methods for individual trees can be evaluated with manually measured stand-level parameters, i.e. tree height and crown diameter. The resulting CHM generated by a simple subtraction is full of empty pixels (called "pits") that will give vital impact on subsequent analysis for individual tree delineation. The experimental results indicated that if more individual trees can be extracted, tree crown shape will became more completely in the CHM data after the pit-free process.

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.

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.

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.

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.

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.

Liu J.-K.,LIDAR Technology Co. | Lin T.-Y.,LIDAR Technology Co. | Hsu W.-C.,LIDAR Technology Co.
35th Asian Conference on Remote Sensing 2014, ACRS 2014: Sensing for Reintegration of Societies | Year: 2014

Manually delineation of the outer boundaries of submerged rocks of an offshore island is often required for practical use of understanding the extension of the island, coral reefs, shoals and banks in the shallow water. The mapping procedure is affected by optical properties of the water bodies such as water clarity, depth attenuation, bottom reflectance, and scattered suspended material. Since WorldView-2image has more bands than other high resolution satellite imagery, it may provide more information for the mapping. The purpose of this study is to make experiments of three selected enhancement methods for improving the contrast of the outer boundaries of submerged rocks of an offshore island with high spatial resolution imagery. The methods include GBC false color composite, Green Index, and Principal components. The study area is located in the southeast offshore isle of Taiwan know as Green Isle, a volcanic island. The results show that (1) Both GBC false color composite and images of green indices can give better interpretation than the original images or RGB images of any combinations of individual bands; (2) For various combinations of principal components, the false color composite with PC6, PC7 and PC8 performs best for visual interpretation of the boundaries.

Liu J.-K.,LIDAR Technology Co. | Chang H.-C.,LIDAR Technology Co. | Hsu W.-C.,LIDAR Technology Co.
35th Asian Conference on Remote Sensing 2014, ACRS 2014: Sensing for Reintegration of Societies | Year: 2014

Typhoon Morakot attacked Taiwan on 6th August 2010 and exhibited a historical record of accumulated rainfall of 2854 mm in 3 days. Hsiaolin Village was smashed by the massive debris flow originated from the deep-seated Hsiaolin Landslide. Unanimously, the trigger factor was rainfall. Nevertheless, there have been a lot of debates with controversial remarks about the cause of the deep-seated landslide. The purpose of this study is to check the land surface evidences related to pre-clues of the landslide with historical aerial photographs. In total, 15 aerial photographs in 6 years are used in this study, i.e. 1966, 1982, 1988, 2002, 2005, and 2007. Firstly, parameters of Interior Orientation for various types of aerial camera are applied. Then, orthophotos of the area acquired right before Morakot Event are used for geodetic control and airborne LiDAR digital surface model (DSM) acquired in 2005 are used for vertical control. Thirdly, all stereo-pairs of various years are used to generate DSM and orthophotos for the respective year. Finally, comparisons of the orthophotos and DSM in various years are made to check the topographic change in sequence of time. The accuracy of aerial triangulation is around one meter. No ground cracks or fissures can be observed before Morakot event. This may imply that no obvious deformation took place before the event or the deformation features were hidden by forest cover. Nevertheless, it was observed that the outer shape of deforestation area on 1988 photos coincided with the crown area of the deep-seated landslide. Further observation of the large-scaled landslides in the neighborhood revealed that the crown boundaries are mostly coincided with deforestation boundaries. This may indicate a link between activities of deforestation and deep-seated landslides for this study area.

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