1,632 research outputs found
Geodetic satellite altimeter study - A review of electromagnetic scattering from the ocean surface
Electromagnetic wave scattering by sea surfaces relevant to geodetic satellite altimeter desig
Stability of Coalescence Hidden variable Fractal Interpolation Surfaces
In the present paper, the stability of Coalescence Hidden variable Fractal
Interpolation Surfaces(CHFIS) is established. The estimates on error in
approximation of the data generating function by CHFIS are found when there is
a perturbation in independent, dependent and hidden variables. It is proved
that any small perturbation in any of the variables of generalized
interpolation data results in only small perturbation of CHFIS. Our results are
likely to be useful in investigations of texture of surfaces arising from the
simulation of surfaces of rocks, sea surfaces, clouds and similar natural
objects wherein the generating function depends on more than one variable
The identification of cloud types in LANDSAT MSS images
The author has identified the following significant results. Five general families of clouds were identified: cumulonimbiform, cumuliform, stratiform, stratocumuliform, and cirriform. Four members of this five-fold primary division of clouds were further divided into a number of subgroups. The MSS observed and recorded earth radiation in four different wavebands. Two of these bands (4 and 5) image in the visible portion of the electromagnetic spectrum, while the others (6 and 7) image the short wave portion, or just into the infrared. The main differences between the appearances of clouds in the four wavebands are related to the background brightness of land and sea surfaces
Mass transfer of carbon dioxide across sea surfaces
The rate of mass transfer of carbon dioxide across the sea surface was investigated in the laboratory and at sea. In the laboratory, radioactive tracer techniques were employed using high specific activity C14O2. The equilibrium distribution of CO2 is not affected greatly and the mass transfer measured is very nearly the exchange coefficient...
Global geochemical problems
Application of remote sensing techniques to the solution of geochemical problems is considered with emphasis on the 'carbon-cycle'. The problem of carbon dioxide sinks and the areal extent of coral reefs are treated. In order to assess the problems cited it is suggested that remote sensing techniques be utilized to: (1)monitor globally the carbonate and bicarbonate concentrations in surface waters of the world ocean; (2)monitor the freshwater and oceanic biomass and associated dissolved organic carbon; (3) inventory the coral reef areas and types and the associated oceanographic climatic conditions; and (4)measure the heavy metal fluxes from forested and vegetated areas, from volcanos, from different types of crustal rocks, from soils, and from sea surfaces
Area Estimation of Deep-Sea Surfaces from Oblique Still Images
Estimating the area of seabed surfaces from pictures or videos is an important problem in
seafloor surveys. This task is complex to achieve with moving platforms such as submersibles,
towed or remotely operated vehicles (ROV), where the recording camera is typically
not static and provides an oblique view of the seafloor. A new method for obtaining seabed
surface area estimates is presented here, using the classical set up of two laser devices
fixed to the ROV frame projecting two parallel lines over the seabed. By combining lengths
measured directly from the image containing the laser lines, the area of seabed surfaces is
estimated, as well as the camera’s distance to the seabed, pan and tilt angles. The only
parameters required are the distance between the parallel laser lines and the camera’s horizontal
and vertical angles of view. The method was validated with a controlled in situ experiment
using a deep-sea ROV, yielding an area estimate error of 1.5%. Further applications
and generalizations of the method are discussed, with emphasis on deep-sea applications
Modeling Broadband Ocean Acoustic Transmissions with Time-Varying Sea Surfaces
Solutions to ocean acoustic scattering problems are often formulated in the frequency domain, which implies that the surface is frozen in time. This may be reasonable for short duration signals but breaks down if the surface changes appreciably over the transmission time. Frequency domain solutions are also impractical for source-receiver ranges and frequency bands typical for applications such as acoustic communications (e.g. hundreds to thousands of meters, 1-50 kHz band). In addition, a driving factor in the performance of certain acoustic systems is the Doppler spread, which is often introduced from sea-surface movement. The time-varying nature of the sea surface adds complexity and often leads to a statistical description for the variations in received signals. A purely statistical description likely limits the insight that modeling generally provides. In this paper, time-domain modeling approaches to the sea-surface scattering problem are described. As a benchmark for comparison, the Helmholtz integral equation is used for solutions to static, time-harmonic rough surface problems. The integral equation approach is not practical for time-evolving rough surfaces and two alternatives are formulated. The first approach is relatively simple using ray theory. This is followed with a ray-based formulation of the Helmholtz integral equation with a time-domain Kirchhoff approximation
On combining satellite altimetry with hydrographic data
It is shown, by random construction of many sea surfaces, each consistent with geostrophy and mass conservation in the underlying ocean, that absolute sea surface topography relative to a geopotential surface can be estimated to 10 cm accuracy from appropriate in situ measurements of density...
A theory of microwave apparent temperature over the ocean
In the microwave region combined active (scatterometer) and passive (radiometer) remote sensors over the ocean show promise of providing surface wind speeds and weather information to the oceanographer and meteorologist. This has aroused great interest in the investigation of the scattering of waves from the sea surface. A composite surface scattering theory is investigated. The two-scale scattering theory proposed by Semyonov was specifically extended to compute the emmision and scattering characteristics of ocean surfaces. The effects of clouds and rain on the radiometer and scatterometer observations are also investigated using horizontally stratified model atmospheres with rough sea surfaces underneath. Various cloud and rain models proposed by meteorologist were employed to determine the rise in the microwave temperature when viewing downward through these model atmospheres. For heavy rain-fall rates the effects of scattering on the radiative transfer process are included
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