Analysis of Land and Sea Area Identification using GPS-Reflections Daeyun Shin, Dinesh Manandhar, Ryosuke Shibasaki Centre for Spatial Information Science The University of Tokyo shindy@iis.u-tokyo.ac.jp ABSTRACT Bi-static remote sensing using GPS signal (direct and reflect signals) has become a new application where GPS/GNSS signals are used besides its main purpose of positioning, navigation and timing applications. The characteristics of reflected electromagnetic wave are affected by the object that reflects the signal. The coefficient of reflection depends upon the dielectric properties of the material and the incidence angle of the wave to the reflecting object. The dielectric properties of water and dry soil differ by 80 times. Thus, there will be big difference of amplitude of reflected signal from water and dry soil. The reflected signal characteristics are also affected by the polarization of the signal and the antennas to receive the signals. GPS signal is right hand circular polarization. The polarization of the signal may change from right hand to left hand when the signal is reflected. Right hand circular polarization antenna is used to receive direct signal and left hand circular polarization antenna is used to receive reflect signal. A comparative analysis of left hand circular polarization signal is done with respect to right hand circular polarization signal to compute code phase delay and signal amplitude. These values are used for developing models to identify the characteristics of reflecting materials. In this research, we would like to study the possibilities of identifying land and sea areas. INTRODUCTION Researchers have been using reflected GPS signal as a source of information for remote sensing application. All these applications are based on bi- static remote sensing, in which two antennas (transmitting and receiving) are separated by quite a large distant and may be on different platforms. Some of the references are [2], [10] for soil moisture, [5], [9] for wind velocity over ocean. We are doing various analysis using different types of platforms, antennas and front-end devices to study and analyze GPS reflected signal. In this paper, we will present about our studies related with data collected from Cessna aircraft flown over sea and land using RHCP and LHCP antennas. The data acquired by the front-end devices are processed to calculate the range delay and power amplitude of reflected signal with respect to direct signal. Our goal is to analyze whether it will be possible to differentiate between the signals reflected from the ground (non-water body) and sea (or water body). SYSTEM ARCHITECTURE The data logger consists of a dual-antenna front- end device. It down-converts the signal from GPS L1 band, 1.57542 GHz to an intermediate frequency at 4.1304 MHz and digitize it at 4 bits at a sampling frequency of 16.3676 MHz. Same clock is used for both the antenna down-converters in order to synchronize the data from two antennas and to have the same