HOME | CONTENTS | GEOLOGIC DISCUSSION | DATA/GIS | METADATA | REFERENCES | CONTACTS

Table of Contents:

OF 2004-1014

Disc Contents

Geologic Discussion

Data/GIS

• Getting Started

• Navigation

• Seismic-reflection

• Sidescan-sonar mosaics

• Ground-Truthing

Metadata/Data
    Catalog

References Cited

Contacts

SIDESCAN-SONAR MOSAICS

As described in the Geologic Discussion, the sidescan-sonar imagery was collected using an SIS-1000 system. The sidescan-sonar imagery enabled detailed mapping of the surficial geology of the reservoir floor. This imagery is presented such that a strong acoustic signal (backscatter) is white and a weak backscatter signal is black. The digitally acquired data were processed and mapped to provide proper geographic locations of features identified in the imagery. The processing steps included subsampling the raw sidescan-sonar data using median filtering to suppress speckle noise and reduce file size. Other steps included correcting for slant-range distortion, signal attenuation, and dropped sonar pings. These initial processing steps were accomplished using XSonar software package (Danforth and others, 1991). The individual sidescan swaths were then mapped with each pixel geographically positioned at a resolution of 2 m/pixel using techniques summarized by Paskevich (1996). Individual swaths were then mosaicked into a continuous cover image to serve as the base map for ground truth work in the reservoir. This mosaic was mapped at a resolution of 2 m/pixel, in Washington State Plane South, NAD83 projection. Due to the size of the reservoir, two mosaics were created. One for the eastern end of the reservoir, and one for the western portion. These images are available in the data/sidescan/stateplane folder. These segments are also available in a geographic coordinate system in the data/sidescan/geographic folder. The mosaics were combined into a single mosaic in a MrSid image format, available in the Washington State Plane South projection, as well as geographic coordinates.