Remote Sensing

This dual conception of remote sensing brought us to the idea of preparing two different books; in addition to the first book which displays recent advances in remote sensing applications, this book is devoted to new techniques for data processing, sensors and platforms. We do not intend this book to cover all aspects of remote sensing techniques and platforms, since it would be an impossible task for a single volume. Instead, we have collected a number of high-quality, original and representative contributions in those areas

STATISTICAL PROPERTIES OF OCEAN SURFACE HEIGHTS USING REMOTE SENSORS WITH VARIABLE LINE OF SIGHT ANGLE

ABSTRACT Numerical relationships to obtain information concerning some statistical properties of surface heights from statistical properties of the intensities in a sea surface image, via remote sensing, are presented. A expression between variance of the intensity in the image and surface slopes and the association between correlation functions of the intensities in the image and surface slopes are analyzed using an improve model with variable detector angle. The one-dimensional case is analyzed and the results are presented graphically

Space-borne application of GNSS reflectometry for global sea state monitoring

This research focuses on modelling the relationship between wind conditions, sea roughness and GNSS reflections received from Low Earth Orbit (LEO). The motivation for this study lies in the recent development of a GNSS reflections receiver platform for the UK-DMC satellite and the numerous advantages proposed GNSS Reflectometry can provide in Earth Observation and global disaster monitoring. The fIrst part of the thesis focuses on the simulation procedure of received GPS-R Delay-Doppler Map (DDM). Airborne GPS-R scatterometric model has been adapted into this space-borne application research. Aft~r deriving DDM simulations according to reflection scenario, the results of two-dimensional data-model fItting are presented and analysed. The sensitivity discussion of current GPS-R model suggests some limitations of the modelling method, especially under medium and high wind speed ranges. In the second part, we investigate the inversion scheme of DDMs for the purpose of extracting a statistical wave model empirically. The similar model structure of DDM simulation is used but the processing order is turned over. After deconvolution, DDMs are inversed back to spatial energy maps and spatial slope probability maps. Three inversion algorithms are developed and compared. Preliminary synthetic and real data experiments give evidence of the feasibility of the inversion methodology. Finally, in the third part of this research, a new geometric wave slope statistical model is discussed in the context of wave fIeld simulations. The sensitivity of obtained statistical model is discussed in terms of wind speed, wave direction and observing incident angle. This provides an alternative view point to look into the wave slope probability properties and compensate the traditional theoretic and empirical wave modelling methods. Key words: GNSS-Reflectometry, Delay-Doppler Map inversion, wind conditions, sea surface roughness, slope probability density function, statistical wave slope model.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Specular point scattering contribution to the mean Synthetic Aperture Radar image of the ocean surface

n general, the return signal scattered from the ocean surface used to form synthetic aperture radar (SAR) images contains contributions from at least two scattering mechanisms. In addition to resonant Bragg‐type scattering, specular point scattering becomes important as the angle of incidence becomes small ( ≲ 20°). In this paper we include the specular point rough surface scattering mechanism in a model for the mean SAR image of the ocean surface and examine the effects of this scattering mechanism theoretically. We find that the complete mean SAR intensity image consists of a sum of images due to specular point scattering and Bragg‐type resonant scattering. Because surface specular points have a short coherence time and move with considerable velocities, the contribution to the mean image due to these scatterers is of low azimuthal resolution and is displaced from the actual sea surface, typically by several SAR resolution cells. The bandwidth of this image can easily exceed the bandwidth of a typical SAR processor, leading to a loss of mean image intensity. The local backscatter cross‐section modulation is strong and nonlinear in the slope of the longwave field in the SAR range direction. At small incidence angles, this causes the specular point return from wave slopes tipped toward the SAR to become much brighter than the Bragg‐scattering return. Taken together, these effects are capable of producing azimuthally oriented streaks in SAR images, such as have been observed by Seasat. We present numerical estimates of coherence time, azimuthal displacement, cross‐section modulation, etc., computed using the parameters of the Seasat and shuttle imaging radar‐B SARs as well as typical parameters for an airborne X band SA

Speckle Effects in Target-in-the-Loop Laser Beam Projection Systems

In target-in-the-loop laser beam projection scenarios typical of remote sensing, directed energy, and adaptive optics applications, a transmitted laser beam propagates through an optically inhomogeneous medium toward a target, scatters off the target’s rough surface, and returns back to the transceiver plane. Coherent beam scattering off the randomly rough surface results in strong speckle modulation in the transceiver plane. This speckle modulation has been a long-standing challenge that limits performance of remote sensing, active imaging, and adaptive optics techniques. Using physics-based models of laser beam scattering off a randomly rough surface, we show that received speckle-field spatial and temporal characteristics can be used to evaluate the intensity distribution of the beam projected onto the target. We derive analytical expressions that directly couple the measured target-return wave statistical characteristics, or ‘speckle metrics’, with characteristics of the laser beam intensity distribution on the target surface. We also show how measured speckle metrics can be utilized for evaluation of laser beam quality at the target surface and for adaptive compensation of atmospheric turbulence-induced phase aberrations