In quest of the grid

Böhm, Gualtiero; Vesnaver, Aldo

doi:10.1190/1.1444618

Cited by 46 publications

(25 citation statements)

References 33 publications

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“…Intuitively, this corresponds to at least two rays crossing each bin. In spite of this severe limitation, a meaningful retrieval can be achieved following a nonregular grid as suggested by [Bohm and Vesnaver, 1999]. We start with 39 bins and proceed to group them horizontally when they are crossed by the same rays imposing horizontal continuity, and to group them vertically using an ''a priori'' vertical structure of the atmosphere.…”

Section: System Geometry and Forward Modelingmentioning

confidence: 99%

“…[4] The tomographic technique introduced in this work is widely applied in seismology for the determination of the propagation velocity of elastic waves [Bohm and Vesnaver, 1999]. Through its application, it is possible to obtain the specific absorption of the atmosphere, from sky observations by a radiometer operating at a single frequency.…”

Section: Introductionmentioning

confidence: 99%

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Retrieval of two‐dimensional absorption coefficient structure from a scanning radiometer at 23.8 GHz

Bosisio

Drufuca

2003

Radio Science

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[1] In this work the retrieval of the structure of the atmospheric specific absorption coefficient through a tomographic acquisition is discussed. Brightness temperatures have been collected daily at 23.8 GHz using a radiometer in tipping curve mode regardless of the sky condition, except for rainy days, for about 60 elevation scans. Each scan has been processed to retrieve the two-dimensional structure of the underlying atmosphere through the (x-z) values of the specific absorption coefficient. The forward model is inverted after binning in space and linearization around a reference model. The scanned vertical plan is modeled by allocating M bins spanning in both the vertical and the horizontal direction, whereas the measurements have been collected at 12 elevation angles between 23°and 90°. Singular value decomposition allows identifying an orthogonal basis for the data space (12 elevation angles) and for the model space (M bins). It indicates also that only five eigenvalues are such that the condition number of the matrix representing the linearized problem is acceptable (%20), so that only five components of the model space may be resolved. A higher number would imply unacceptable noise contamination. In spite of these limitations, the retrieved panel of specific absorption coefficient reveals the horizontal structure of the atmosphere. The scale of the experiment is of the order of kilometers. Therefore, because the vertical structure of the atmosphere dominates over the horizontal, a vertical detrending is needed to reveal horizontal structures. An example shows the typical problems encountered in the inversion and the remedies that have been adopted.INDEX TERMS: 0933 Exploration Geophysics: Remote sensing; 6994 Radio Science: Instruments and techniques; 3260 Mathematical Geophysics: Inverse theory; KEYWORDS: water vapor absorption, radiometry, tomography, inversion Citation: Bosisio, A. V., and G. Drufuca, Retrieval of two-dimensional absorption coefficient structure from a scanning radiometer at 23.8 GHz,

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Section: System Geometry and Forward Modelingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Retrieval of two‐dimensional absorption coefficient structure from a scanning radiometer at 23.8 GHz

Bosisio

Drufuca

2003

Radio Science

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“…This time stability provides opportunity for certain level of grid optimization according to the particular measurement set up. By modifying the grid accordingly we can increase the tomographic resolution (using smaller grid point separations) at locations where more observations cross and reduce the resolution (using larger grid point separations) for areas covered less by observations (Böhm and Vesnaver 1999).…”

Section: The Tomographic Techniquementioning

confidence: 99%

Ground-Based GPS Tomography of Water Vapor: Analysis of Simulated and Real Data

Gradinarsky

Jarlemark

2004

Journal of the Meteorological Society of Japan

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We present the concept, some of the approaches used, and the capabilities of the technique referred to as GPS tomography. It is used for retrieval of the 3-dimensional distribution of the refractivity due to atmospheric water vapor. We discuss the presently used methods for retrieval of the primary observable in the GPS tomography, the slant path delay, as well as their shortcomings. Comparisons of GPS slant delays to independent data from a microwave radiometer are included. From a tomographic point of view we concentrate on the capabilities to retrieve the vertical structure of the wet refractivity. For this purpose we present and apply two methods for tomographic inversion. Both are based on the Kalman filtering technique, where the expected statistical behavior of the refractivity is utilized. The difference between the two is in the way the covariance matrix of the Kalman filter is constructed. We base our study on simulated and real data from the ground network of 8 GPS receivers operating in Göteborg, Sweden. The results demonstrate that at present the limitations of the GPS tomographic technique are errors in the retrieved wet slant delays and their poor geometric distribution.

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“…A further tomographic analysis was computed using the "staggered grid" method (Böhm and Vesnaver, 1999), a procedure implemented in another tomographic package (Cat3d). This method uses a single grid, called base grid, on which different shifts in space are applied along X, Y and Z Near Surface Geoscience Turin, Italy, 6-10 September 2015 directions.…”

Section: Tomographic Analysismentioning

confidence: 99%

Photogrammetry and 3-D Ultrasonic Tomography to Estimate the Integrity of Two Sculptures of the Egyptian Museum of Turin

Sambuelli¹,

Böhm²,

Colombero³

et al. 2015

Near Surface Geoscience 2015 - 21st European Meeting of Environmental and Engineering Geophysics

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SUMMARYWe present a fruitful combination of geophysical tests (Ultrasonic Measurements) and photogrammetric processing (Structure from Motion) for the analysis of the integrity of a couple of statues from the Egyptian Museum of Turin. Aim of the study was to investigate the persistence of the exterior widespread fractures within the sculptures. More than one hundred ultrasonic measurements were acquired on selected travel-paths across each statue, using an ultrasonic pulse velocity instrument. Dealing with complex-shape objects of restrained dimensions, it was very important to accurately define the three-dimensional coordinates of sources and receivers, in order to precisely measure their distances. A 3-D model of the statues was obtained from photogrammetric techniques. The acquired data were analyzed with both a statistical approach and tomographic processing, comparing the use of classical and staggered grids, in order to obtain the best fit of the local resolution. The final results revealed a valuable tool to guide the procedures for the mobilization, transport and restoration of the sculptures.

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In quest of the grid

Cited by 46 publications

References 33 publications

Retrieval of two‐dimensional absorption coefficient structure from a scanning radiometer at 23.8 GHz

Retrieval of two‐dimensional absorption coefficient structure from a scanning radiometer at 23.8 GHz

Ground-Based GPS Tomography of Water Vapor: Analysis of Simulated and Real Data

Photogrammetry and 3-D Ultrasonic Tomography to Estimate the Integrity of Two Sculptures of the Egyptian Museum of Turin

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