Mitsuharu Tokunaga

Filtering Airborne Laser Scanner Data: A Wavelet-Based Clustering Method

Filtering the airborne laser scanner data is challenging due to the complex distribution of objects on Earth’s surface and it is still in development stage. This problem has been investigated so far with varieties of algorithms, but they suffer from different magnitudes of drawbacks. This study proposed a new and improved hybrid method based on multi-resolution analysis. Wavelet was adopted in this multi-resolution clustering approach. It enabled the classification of objects based on their size and the efficiency to filter out unwanted information at a specific resolution, and the proposed algorithm is named the ALSwave (Airborne Laser Scanner Wavelet) method. ALSwave has been tested on two data sets acquired over the urban areas of Tokyo, Japan and Stuttgart, Germany. The results showed a well-filtered, bare earth surface coupled with acceptable computational time. The accuracy assessment was carried out by comparison between the filtered bare earth surface by ALSwave and the manually filtered surface. The Root Mean Square Error (RMSE) follows a linear relationship with respect to terrain slope. This wavelet-based approach has opened a new way to filter the raw laser data that subsequently generates fast and more accurate digital terrain models.

Wavelet-based extraction of building features from airborne laser scanner data

A new approach based on wavelet analysis to detect buildings in a dense urban area from airborne laser scanner data is presented in this paper. Without the spectral reflectance from the buildings, their detection from the laser cloud points is mainly based on the discrimination of the buildings elevation and its surroundings. This detection becomes more challenging in a dense urban area, which contains skyscrapers, interspersed with a myriad of low and small as well as large houses along with crowded outdoor human activities. Integration of the objects size and its elevation could mitigate the difficulty of detection. Wavelet analysis was proposed and adopted to build up the framework for size-based detection. The study focused on the detection of buildings and the generation of a three-dimensional (3D) building database. The extractable information from the aerial photographs is optional. The proposed approach was tested in Shinjuku-ku, Tokyo, Japan, and the result has successfully matched with the existing two-dimensional (2D) vector data. Wavelet-based multi-resolution has proved an appropriate approach in eliminating the unnecessary features surrounding buildings and in extracting the buildings.

Wavelet-based system for classification of airborne laser scanner data

A new semi-automatic processing system for classification of airborne laser scanner cloud points is developed. To mitigate the difficulty caused by the complex distribution of objects on Earths surface, wavelet was adopted in size-based clustering of laser points. A hybrid method of processing laser scanner data in both grid and raw formats was also adopted to speed up the processing time and adjust the smoothing effect of interpolation. The processing focused on processing the data acquired over urban area. This paper presents and explains the components of the system using the test data acquired over Shinjuku area, Tokyo, Japan.

The utility of renewal system for barrier-free map by using remote sensing and RTK-GPS

Research proposed that wheelchair user uses remote sensing (RS), Real-Time Kinematic-Global Positioning System (RTK-GPS) and Geographic Information System (GIS) support to make barrier-free map. In this paper, Remote Sensing means high-resolution satellite imageries. If equipment of RTK-GPS attach to wheelchair, barrier-free map can be able to revise as the imageries on computer every day. Wheelchair users always can get the latest information of urban conditions. Proposed system automatically make barrier-free map. In other words, it suggests that mapping process dose not need much labor and time. In addition, the system as mentioned above makes more useful barrier-free map using Remote Sensing imageries as a background. Combination of remote sensing, RTK-GPS and GIS applied to barrier-free map prepared by local government improve rapidly life style for wheelchair users

Detection of Volcanic Deposits on Mount Mayon Using SAR Interferometry

Abstract Eruption of Mount Mayon causes severe loss of human life and damage to property. The main damage is caused during an eruption and from subsequent erosion of the deposited material. Heavy rainfall in the Mayon area erodes volcanic deposits, mainly pyroclastic and ash deposits, which flow as lahar to the foothill of the mountain. These lahar flows cause drastic damage to the economically important areas. It is therefore important to detect the volcanic deposits on Mount Mayon to develop mitigation plans for future disasters. In this study an attempt was made to apply the SAR interferometric technique to detect the volcanic deposits. Using interferometric technique, height of the volcanic deposits of February 1993 eruption on Mount Mayon were identified with the accuracy of 5 to 10 meters.

Updating geomorphic features of watersheds and their boundaries in hazardous areas using satellite synthetic aperture radar.

Volcanic disasters can cause severe loss of human life and damage to property. The main damage is caused during an eruption and from subsequent erosion of deposited materials. Heavy rainfall in volcanic areas erodes volcanic deposits, mainly pyroclastic flows and ash fall deposits, which flow as lahar to the foothill of the mountain and cause drastic damage to economically important areas. This post-eruption disaster becomes complex due to the occurrence of stream captures and watershed breakouts that lead to devastating lahars. Continuous monitoring of such geomorphic and hydrologic changes is necessary to cope with changing hazard conditions. Therefore it is important to update the watershed boundaries in order to study current hazard conditions and develop mitigation plans for future disasters. Changes of geomorphic and watershed boundary have occurred in the Mayon Volcano in the Philippines mainly as a result of a major volcanic eruption of 1993, due to which mitigation structures were constructed and modified in the low lying areas. In this study interferometry was used to develop DEM from SAR data to delineate watershed boundaries. New lava flows, pyroclastic flows and lahar deposits in the watersheds were mapped using elevation changes, coherence and intensity derived from the SAR images. Updating geomorphic features of the watersheds and their boundaries using SAR provides a new weather independent alternative technique for monitoring the effect of volcanic activity.

Accuracy verification of DSM obtained from UAV using commercial software

Recently, some commercial software to generate digital surface model (DSM) were provided from some vender. One software is based on the bundle method using conventional Photogrammetry, another one is based on structure-from-motion method (SfM) under computer graphics technology. It is wavered to choose which software to generate DSM derived from drones. In this work, the accuracies of DSM were verified using the software such as Image Master (TOPCON), PhotoScan (Agisoft) and Postflight Tera 3D (sensefly). The experiments carried out some cases that UAVs height and camera resolution were changed. UAV also were used both of the fixed wing type and the rotor wing type. The results show that the software based on SfM provides the precisely centimeter order DSM without the ground control points (GCP) and the deference of accuracy by UAVs altitude shows non-linear using the camera with the lens distortion is large.

3-D viewed vegetation landscapes generated from day and night time AVHRR data

Uses daytime and nighttime AVHRR data to characterize terrain environments. The 3-D terrain view, draped on the CC image of three AVHRR derived bands, daytime vegetation temperature index (VTI), day-nighttime temperature difference (DT) and LSTn-derived elevation (ELE), illustrated vegetation landscapes in which can be used for forest degradation on fragile highland and monitoring topographic-based land uses.