GLORIA image processing: The state of the art

Searle, R. C.; Bas, Tim Le; Mitchell, Neil C.; Somers, M. L.; Parson, L. M.; Patriat, P.

doi:10.1007/bf00310560

Cited by 39 publications

(11 citation statements)

References 4 publications

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“…Details of the technical specification, data acquisition, processing and interpretation of GLORIA images have been included in a number of recent reviews (e.g. Somerset al, 1978;Laughton, 1981;Chavers, 1986;Searle et al, 1989), and only the main points are reiterated here. For the purpose of the interpretation of data presented in this paper, the GLORIA sonographs, all of which here have a total swath width of 45 kin, may be considered to record levels of energy backscattered from features or 'targets' to the seafloor.…”

Section: New Datamentioning

confidence: 99%

Segmentation of the Central Indian Ridge between 12°12′ S and the Indian Ocean Triple Junction

et al. 1993

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Abstract. The present morphology and tectonic evolution of more than 1500 kilometres of the Central Indian Ridge are described and discussed following the integration of GLORIA side-scan sonographs with conventional geophysical datasets. Segmentation of the ridge occurs by a series of ridge axis discontinuities ranging in periodicity along strike from 275 km to less than 30 km. These segment boundaries we have classified into two types: first order fracture zones of offsets greater than 50 km which bound five major. (mega-) segments, and smaller scale structures of a variety of offset styles and amplitudes which cut four of these segments. We refer to these as ridge-axis discontinuities. The frequent opposite sense of offset identified between the first order structures and the subordinate discontinuities between these major structures is interpreted as resulting from the adjustment to new kinematic parameters after magnetic anomaly 20. As far as our data allows us to determine, the central major segment is not subdivided by minor ridge axis discontinuities, which we suggest is a result of its proximity to the Rodriguez hotspot.

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Section: New Datamentioning

confidence: 99%

Segmentation of the Central Indian Ridge between 12°12′ S and the Indian Ocean Triple Junction

et al. 1993

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“…These images were digitally mosaicked and then merged with the Seabeam bathymetry data. This processing was performed with the Mini Image Processing System (MIPS) developped at the USGS and IOSDL (Chavez, 1986;Searle et al, 1990).…”

Section: Data Processing and Compilationmentioning

confidence: 99%

Structural analysis of the segmentation of the Central Indian Ridge between 20�30?S and 25�30?S (Rodriguez Triple Junction)

Briais

1995

Mar Geophys Res

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Abstract. The morphological characteristics of the segmentation of the Central Indian Ridge (CIR) from the Indian Ocean Triple Junction (25°30'S) to the Egeria Transform Fault system (20°30'S) are analyzed. The compilation of Sea Beam data from R/V Sonne cruises SO43 and SO52, and R/V Charcot cruises Rodriguez t and 2 provides an almost continuous bathymetric coverage of a 450-km-long section of the ridge axis. The bathymetric data are combined with a GLORIA side-scan sonar swath to visualize the fabric of the ridge and complement the coverage in some areas. This section of the CIR has a full spreading rate of about 50 mm yr -~, increasing slightly from north to south. The morphology of the CIR is generally similar to that of a slow-spreading center, despite an intermediate spreading rate at these latitudes. The axis is marked by an axial valley 5 35 km wide and 500-1800 m deep, sometimes exhibiting a 100-600 m-high neovolcanic ridge. It is offset by only one 40-km offset transform fault (at 22°40'S), and by nine second-order discontinuities, with offsets varying from 4 to 21 km, separating segments 28 to 85 km long. The bathymetry analysis and an empirical orthogonal function analysis performed on across-axis profiles reveal morphologic variations in the axis and the second-order discontinuities. The ridge axis deepens and the relief across the axial valley increases from north to south. The discontinuities observed south of 22°S all have morphologies similar to those of the.slowspreading Mid-Atlantic Ridge. North of 22°S, two discontinuities have map geometries that have not been observed previously on slow-spreading ridges. The axial valleys overlap, and their tips curve toward the adjacent segment. The overlap distance is 2 to 4 times greater than the offset. Based on these characteristics, these discontinuities resemble overlapping spreading centers (OSCs) described on the fast-spreading EPR. The evolution of one such discontinuity appears to decapitate a nearby segment, as observed for the evolution of some OSCs on the EPR. These morphological variations of the CIR axis may be explained by an increase in the crustal thickness in the north of the study area relative to the Triple Junction area. Variations in crustal thickness could be related to a broad bathymetric anomaly centered at 19°S, 65°E0 which probably reflects the effect of the nearby R6union hotspot, or an anomaly in the composition of the mantle beneath the ridge near 19°S. Other explanations for the morphological variations include the termination of the CIR at the Rodriguez Triple Junction or the kinematic evolution of the triple junction and its resultant lengthening of the CIR. These latter * Now at: GRGS-UMR 39, CNRS, Observatoire Midi-Pyr6n6es,

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“…Images of signal backscattered from the seabed are a montage of image textures arising in large part from the backscattering characteristics of seabed materials. A sonar image is rendered more interpretable in terms of distributions of seabed materials if confounding nonseabed effects are corrected for (e.g., Reed and Hussong [9]; Searle et al [10]; Augustin and Lurton [11]), and effects of the seabed that are a function of angle are normalized to the effect at a reference angle. We summarize these effects as due to: 1) absorption by travel through water; 2) geometrical spreading (incorporating the area of the seabed ensonified by the sonar pulse); 3) the sonar beam function (i.e., the responses for the sonar's port and starboard transmitting-receiving transducer arrays verses inclination angle with respect to the sonar's reference frame); in this paper Beam Function is abbreviated to BF); 4) sonar vehicle roll; 5) seabed backscatter functions (the backscattering ratio response verses inclination angle with respect to the seabed's frame of reference-or grazing angle; in every day speech we refer to one of these as a Scatter Function and the abbreviation SF is employed in the paper); and 6) seabed slope.…”

Section: Introductionmentioning

confidence: 99%

Sidescan Sonar Beam Function and Seabed Backscatter Functions From Trace Amplitude and Vehicle Roll Data

2016

IEEE J. Oceanic Eng.

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A sidescan sonar's beam function (BF) (the sonar's transmit-receive response versus inclination angle in the sonar's frame of reference) can be extracted from an ensemble of contiguous sonar traces affected by sonar vehicle roll for a uniform seabed. The rotation of the sonar's frame of reference relative to the seabed's frame of reference is employed to extract a number of discrete overlapping beam subfunctions each with angular extent corresponding to the extent of vehicle roll. These are then reconciled to form a composite sonar BF. A seabed backscatter function (SF) (the backscatter response of the seabed versus inclination angle in the seabed's frame of reference) may subsequently be inferred with respect to the BF from trace data, whether affected by roll or not. Independent sonar BF and seabed SFs allow the effect of sonar vehicle roll to be corrected when BF compensation is applied to images, and the effect of seabed slope to be corrected when SF compensation is applied. In an alternate approach to extracting a sonar BF, a seabed SF may be extracted first from the sonar traces affected by vehicle roll, by extracting a number of overlapping backscatter subfunctions, and reconciling these into a composite SF. The sonar BF may then be inferred from the trace data with respect to the SF. Seabed SFs inferred from trace data with respect to the BF may be used as a basis for seabed characterization.Index Terms-Backscatter, beam function, sidescan sonar. 0364-9059

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GLORIA image processing: The state of the art

Cited by 39 publications

References 4 publications

Segmentation of the Central Indian Ridge between 12°12′ S and the Indian Ocean Triple Junction

Segmentation of the Central Indian Ridge between 12°12′ S and the Indian Ocean Triple Junction

Structural analysis of the segmentation of the Central Indian Ridge between 20�30?S and 25�30?S (Rodriguez Triple Junction)

Sidescan Sonar Beam Function and Seabed Backscatter Functions From Trace Amplitude and Vehicle Roll Data

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