Xsonar/ShowImage, a complete system for rapid sidescan sonar processing and display

Danforth, W.W.

doi:10.3133/ofr97686

Cited by 20 publications

(12 citation statements)

References 3 publications

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“…The submerged trees are only visible in the 400 kHz data, possibly explaining why the trees were not systematically located earlier using standard 50 kHz fish-finders. Individual sonar swaths were processed and digitally merged by xsonar (Danforth, 1997) into a seamless, geo-referenced mosaic. The corrected 400 kHz data were mosaiced at 0.2-m resolution, with the final images exported as GeoTIFF files.…”

Section: Methodsmentioning

confidence: 99%

Duration and severity of Medieval drought in the Lake Tahoe Basin

Kleppe

Kent

Biondi

et al. 2011

Quaternary Science Reviews

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a b s t r a c tDroughts in the western U.S. in the past 200 years are small compared to several megadroughts that occurred during Medieval times. We reconstruct duration and magnitude of extreme droughts in the northern Sierra Nevada from hydroclimatic conditions in Fallen Leaf Lake, California. Stands of submerged trees rooted in situ below the lake surface were imaged with sidescan sonar and radiocarbon analysis yields an age estimate of w1250 AD. Tree-ring records and submerged paleoshoreline geomorphology suggest a Medieval low-stand of Fallen Leaf Lake lasted more than 220 years. Over eighty more trees were found lying on the lake floor at various elevations above the paleoshoreline. Waterbalance calculations suggest annual precipitation was less than 60% normal from late 10th century to early 13th century AD. Hence, the lake's shoreline dropped 40e60 m below its modern elevation. Stands of pre-Medieval trees in this lake and in Lake Tahoe suggest the region experienced severe drought at least every 650e1150 years during the mid-and late-Holocene. These observations quantify paleoprecipitation and recurrence of prolonged drought in the northern Sierra Nevada.Published by Elsevier Ltd.

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Section: Methodsmentioning

confidence: 99%

Duration and severity of Medieval drought in the Lake Tahoe Basin

Kleppe

Kent

Biondi

et al. 2011

Quaternary Science Reviews

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“…Side-scan sonar data was processed using USGS, Xsonar and Showimage software as described by Danforth [1997]. A four pixel, across track by three pixel, along track approximately 0.5 meter by 0.5 meter, boxcar filter was used to reduce noise in data.…”

Section: Sampling and Analytical Proceduresmentioning

confidence: 99%

Sediment deposition in the lower Hudson River estuary

Woodruff¹

1999

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This study uses geophysical and sedimentological data collected from the Lower Hudson River estuary to identify the depositional response of the estuary to high river discharge events. Erosional and depositional environments in the estuary are identified through the use of side-scan sonar, bottom penetrating sonar and surficial sediment sampling. Sediment cores are used to document deposit thicknesses and to obtain the spatial distribution of estuarine deposits.Results show a high degree of spatial and temporal variability in sedimen tation within the estuary. Two primary deposits are identified underneath the turbidity maximum for the estuary. Approximately 300,000 metric tons of sed iment were deposited within these two deposits during May and June of 1998. This short-term accumulation underneath the turbidity maximum of the es tuary can account for 30 to 98 percent of the estimated, river-borne sediment load supplied to the estuary during the 1997-1998 water year. Both the tidally produced stratigraphy observed in sediment cores and the spatial distribution of identified deposits, support the theory that sedimentation underneath the turbidity maximum of the estuary is primarily the results of a convergence in bottom water flow, caused by the formation of a salinity front during ebb tide.

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“…The Klein sidescan-sonar data were processed following the methodology of Danforth and others (1991), Danforth (1997), andPaskevich (1996) to remove radiometric and geometric distortions in the raw data. Processed sonar data were mosaicked following the procedures described in Paskevich (1996) using PCI Geomatics OrthoEngine (PCI Geomatics, 2009).…”

Section: Swath Bathymetry and Acoustic Backscattermentioning

confidence: 99%

“…Backscatter data were extracted from the raw SWATHplus data files and converted to USGS Xsonar/Showimage file format (Danforth, 1997) by using SwathEd swath-bathymetric processing software (Hughes Clarke, 1998). Radiometric and geometric distortions in the backscatter data were corrected by using Xsonar/Showimage following the methodology of Danforth (1997). A georeferenced acoustic backscatter mosaic was generated at a pixel resolution of 0.5 m and converted to a TIFF image (Hughes Clarke, 1998).…”

Section: Swath Bathymetry and Acoustic Backscattermentioning

confidence: 99%