OF 2004-1247 HOME

Disc Contents

Introduction

Data/GIS

• Getting Started
  
  
• Interpretation
  
  
• Navigation
  
  
• Seismic-Reflection
  
  
• Sidescan-Sonar
  
  

Metadata/Data Catalog

References Cited

Contacts

Sidescan-Sonar:

More than 362 km of sidescan-sonar imagery were collected using an Edgetech DF1000 system recorded to a Triton Elics QMIPS system. The sonar data were acquired using swath widths of 150m to 600m (ranges 75m to 300m) at an operating frequency of 100 kHz. More information regarding this acquisition system is available on the USGS Woods Hole Science Center SeaFloor Mapping web page.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. The individual sidescan swaths were then mapped with each pixel geographically positioned at a resolution of 2 m/pixel. These initial processing steps were accomplished using XSonar software package (Danforth and others, 1991). Individual swaths were then mosaicked into a continuous cover image using techniques summarized by Paskevich (1996). This mosaic was mapped at a resolution of 2 m/pixel, in UTM, Zone 11, WGS84 projection. These images were subsequently reprojected to UTM, Zone 11, NAD83 as well as a geographic coordinated system. These reprojected TIFF images as well as MrSid compressed images are available from the data/sidescan folder. These images are also available from the sidescan-sonar mosaic section of the Metadata/Data Catalog page.

What follows is a series of images showing the sidescan-sonar coverage of the lake working from north to south. Clicking on any image will open a larger image of the same area.