Crop Field Extraction Method using NDVI and Texture from Landsat TM Images

Shibasaki, Ryosuke,Suzaki, Junichi 대한원격탐사학회 1998 International Symposium on Remote Sensing Vol.14 No.1

Land cover and land use classification on a huge scale, e.g. national or continental scale, has become more and more important because environmental researches need land cover and land use data on such scales. We developed a crop field extraction method, which is one of the steps in our land cover classification system for a huge area. Firstly, a crop field model is defined to characterize $quot;crop field$quot; in terms of NDVI value and textual information. Textual information is represented by the density of straight lines which are extracted by wavelet transform. Secondly, candidates of NDVI threshold value are determined by $quot;scale-space filtering$quot; method. The most appropriate threshold value among the candidates is determined by evaluating the line density of the area extracted by the threshold value. Finally, the crop field is extracted by applying level slicing to Landsat TM image with the threshold value determined above. The experiment demonstrates that the extracted area by this method coincides very well with the one extracted by visual interpretation.

Land Use/Cover Change Study for SE-Asia(LUCS-ASIA)

Shibasaki, Ryosuke,Takagi, Masataka,Twao, Koki 대한원격탐사학회 1995 International Symposium on Remote Sensing Vol.11 No.1

CLIMATE CHANGE IMPACT OVER INDIAN AGRICULTURE - A SPATIAL MODELING APPROACH

Priya, Satya,Shibasaki, Ryosuke 대한원격탐사학회 1999 International Symposium on Remote Sensing Vol.15 No.1

The large-scale distribution of crops is usually determined by climate. We present the results of a climate-crop prediction based on spatial bio-physical process model approach, implemented in a GIS (Geographic Information System) environment using several regional and global agriculture-environmental databases. The model utilizes daily climate data like temperature, rainfall, solar radiation being generated stocastically by in-built model weather generator to determine the daily biomass and finally the crop yield. Crops are characterized by their specific growing period requirements, photosynthesis, respiration properties and harvesting index properties. Temperature and radiation during the growing period controls the development of each crop. The model simulates geographic/spatial distribution of climate by which a crop-growing belt can also be determined. The model takes both irrigated and non-irrigated area crop productivity into account and the potential increase in productivity by the technical means like mechanization is not considered. All the management input given at the base year 1995 was kept same for the next twenty-year changes until 2015. The simulated distributions of crops under current climatic conditions coincide largely with the current agricultural or specific crop growing regions. Simulation with assumed weather generated derived climate change scenario illustrate changes in the agricultural potential. There are large regional differences in the response across the country. The north-south and east-west regions responded differently with projected climate changes with increased and decreased productivity depending upon the crops and scenarios separately. When water was limiting or facilitating as non-irrigated and irrigated area crop-production effects of temperature rise and higher CO₂ levels were different depending on the crops and accordingly their production. Rise in temperature led to yield reduction in case of maize and rice whereas a gain was observed for wheat crop, doubled CO₂ concentration enhanced yield for all crops and their several combinations behaved differently with increase or decrease in yields. Finally, with this spatial modeling approach we succeeded in quantifying the crop productivity which may bring regional disparities under the different climatic scenarios where one region may become better off and the other may go worse off.

A GIS-based Simulation to Predict GPS Availability along the Tehran Road in Seoul, Korea

이양원,서용철,Ryosuke Shibasaki 대한토목학회 2008 KSCE Journal of Civil Engineering Vol.12 No.6

GPS (Global Positioning System) availability is somewhat limited in urban areas because portions of the signals are blocked, reflected, and diffracted by obstructions like buildings. This has been well known through a number of on-site surveys, and recent GIS (Geographic Information System) approaches also simulate the urban GPS availability using 3-D (three-dimensional) terrain data. However, such simulation for skyscraper areas in Seoul, Korea has not been reported yet. Hence, we built a GIS-based prediction model to analyze the GPS availability in terms of LOS (Line of Sight) and DOP (Dilution of Precision), and conducted a simulation for the Tehran Road in Seoul, according to time and location. Our prediction model can show spatiotemporal aspects in GPS availability and apply to examine when and where the navigation services are usable in dense urban areas.

GEO-REFERENCING OF MULTI-SENSOR RANGE DATA FOR VEHICLE-BORNE LASER MAPPING SYSTEM(VLMS)

Manandhar, Dinesh,Shibasaki, Ryosuke 대한원격탐사학회 2000 International Symposium on Remote Sensing Vol.16 No.1

Laser mapping has became quite popular in recent days due to it's capability of providing information directly in three dimension. However, the present laser mapping systems are either air-borne or ground-based (on a static platform). We cannot achieve detail information from air-borne system, though it has it's own suitability for applications like DEM generation. Ground based static systems are not suitable far larger area mapping purpose. The vehicle-borne laser mapping system (VLMS) use laser scanners for three dimensional data acquisition, CCD cameras for texture information, GPS, INS and odometer fax positioning information. The data obtained by this system could be a good resource for developing urban 3D database, which has numerous applications in the field of virtual reality, car navigation, computer games, planning and management. In this paper, we discuss about the system architecture of VLMS, calibration of sensors, integration of all these sensors and positioning devices far direct geo-referencing.

Assessment of Pseudolite Layout under urban Environments Using a Simulation System for Seamless Positioning

Yong-Cheol Sub,Ryosuke Shibasaki 대한토목학회 2003 KSCE journal of civil engineering Vol.7 No.3

Road Network Extraction from High-Resolution Satellite image for GIS Applications

Yongcheol Sub,Huijing Zhao,Ryosuke Shibasaki 대한토목학회 2003 KSCE journal of civil engineering Vol.7 No.5

A Simulation Based Assessment for Evaluating the Effectiveness of Quasi-Zenith Satellite System

Suh, Yong-Cheol,Shibasaki, Ryosuke The Korean Society of Remote Sensing 2003 大韓遠隔探査學會誌 Vol.19 No.3

Since the operation of the first satellite-based navigation service, satellite positioning has played an increasing role in both surveying and geodesy, and has become an indispensable tool for precise relative positioning. However, in some situations, e.g. at a low angle of elevation, the use of satellites for navigation is seriously restricted because obstacles like buildings and mountains can block signals. As a mean to resolve this problem, the quasi-zenith satellite system has been proposed as a next-generation satellite navigation system. Quasi-zenith satellite is a system which simultaneously deploys several satellites in a quasi-zenith geostationary orbit so that one of the satellites always stay close to the zenith if viewed from a specific point on the ground of East Asia. Thus, if a position measurement function compatible with CPS is installed in the quasi-zenith and stationary satellites, and these satellites are utilized together with the CPS, four satellites can be accessed simultaneously nearly all day long and a substantial improvement in position measurement, especially in metropolitan areas, can be achieved. The purpose of this paper is to evaluate the effectiveness of quasi-zenith satellite system on positioning accuracy improvement through simulation by using precise orbital information of the satellites and a three-dimensional digital map. Through this developed simulation system, it is possible to calculate the number of simultaneously visible satellites and available area for positioning without the need of actual observation. Furthermore, this system can calculate the Dilution Of Precision (DOP) and the error distribution.

High Accurate and Efficient Positioning in Urban Areas Using GPS and Pseudolites Integration

SUH, Yong-Cheol,SHIBASAKI, Ryosuke Korean Society of Surveying 2002 Korean journal of geomatics Vol.2 No.1

The Global Positioning System technology has been widely used in positioning and attitude determination. It is well known that the accuracy, availability and reliability of the positioning results are heavily dependent on the number and geometric distribution of tracked GPS satellites. Because of this limitation, in some situations, such as in urban canyons, underground or inside of buildings, it is difficult to navigate with GPS receiver. Therefore, in order to improve the performance of satellite-based positioning, the integration of GPS with the pseudolite technology has been proposed. With this pseudolite technology, it is expected that seamless positioning service can be provided in a wider area without replacing existing GPS receivers. On the other hand, to adopt pseudolites on a larger scale, it is necessary to verify how the pseudolites may complement the existing GPS-based positioning. In this paper the authors present the details of the experiments and the results of the fundamental verification for seamless positioning using integration of GPS and pseudolite. This paper shows that the accuracy and efficiency of integrating GPS and pseudolite through the dynamic and static positioning experiment. The influence of pseudolite signal on GPS receiver is also discussed. The experimental results indicate that the accuracy of the height component can indeed be significantly improved, to approximately the same level as the horizontal component.

Analysis of GPS Signal Acquisition Performance

Xiaofan LI,Dinesh MANANDHAR,Ryosuke SHIBASAKI 한국항해항만학회 2006 한국항해항만학회 학술대회논문집 Vol.2 No.-

Acquisition is to detect the presence of the GPS signal. Once the signal is detected, the estimated frequency and code phase are passed to a tracking loop to demodulate the navigation data. In order to detect the weak signal, multiple length of data integration is always needed. In this paper, we present five different acquisition approaches based on circular correlation and Fast Fourier Transform (FFT), using coherent as well as non-coherent integration techniques for the multiple length of collected GPS satellite signal. Moreover a general approach of determining the acquisition threshold is introduced based on noise distribution which has been proved effective, and independent of the hardware. In the end of this paper, the processing speed and acquisition gain of each method are illustrated, compared, and analyzed. The results show that coherent approach is much more time consuming compared to noncoherent approaches, and in the case of multiple length of data integration from 2ms to 8ms, the processing times consumed by the fastest non-coherent acquisition method are only 25.87% to 1.52% in a single search, and 34.76% to 1.06% in a global search of those in the coherent acquisition. However, coherent acquisition also demonstrates its better performance in the acquisition gain, and in the case of 8ms of data integration it is 4.23 to 4.41 dB higher than that in the non-coherent approaches. Finally, an applicable scheme of combining coherent and non-coherent acquisition approaches in the development of a real-time Software GPS receiver in the University of Tokyo is provided.