Pat S. Chavez

Processing, mosaicking and management of the Monterey Bay digital sidescan-sonar images

Abstract Sidescan-sonar imaging systems with digital capabilities have now been available for approximately 20 years. In this paper we present several of the various digital image processing techniques developed by the U.S. Geological Survey (USGS) and used to apply intensity/radiometric and geometric corrections, as well as enhance and digitally mosaic, sidescan-sonar images of the Monterey Bay region. New software run by a WWW server was designed and implemented to allow very large image data sets, such as the digital mosaic, to be easily viewed interactively, including the ability to roam throughout the digital mosaic at the web site in either compressed or full 1-m resolution. The processing is separated into the two different stages: preprocessing and information extraction. In the preprocessing stage, sensor-specific algorithms are applied to correct for both geometric and intensity/radiometric distortions introduced by the sensor. This is followed by digital mosaicking of the track-line strips into quadrangle format which can be used as input to either visual or digital image analysis and interpretation. An automatic seam removal procedure was used in combination with an interactive digital feathering/stenciling procedure to help minimize tone or seam matching problems between image strips from adjacent track-lines. The sidescan-sonar image processing package is part of the USGS Mini Image Processing System (MIPS) and has been designed to process data collected by any ‘generic’ digital sidescan-sonar imaging system. The USGS MIPS software, developed over the last 20 years as a public domain package, is available on the WWW at: http://terraweb.wr.usgs.gov/trs/software.html .

Integration of geologic, geochemical, and geophysical data of the Cement oil field, Oklahoma, using spatial array processing

Geologic, geochemical, and geophysical measurements were made at the Cement oil field, Oklahoma, test site using airborne and spaceborne sensors coupled with ground‐based data collection. The data collected include (1) airborne gamma‐ray spectrometry (214Bi, 208Tl, 40K, and total intensity channels), (2) low‐altitude aeromagnetic profiles, (3) precision gravity measurements, (4) images from the Landsat multispectral scanner (MSS) systems and U-2 photography, and (5) geologic and topographic maps. In order to reduce, analyze, display, and correlate the information, it was necessary to transform the data from vector space to raster space (a two‐dimensional image array) with fixed resolution and array dimension. With the data in array form, spatial array processing techniques were applied to (1) correct geometrically the data for proper registration, (2) perform areal interpolation and smoothing, (3) display the data as images, and (4) perform integration and correlation studies. Each data set was transforme...

Digital image processing of airborne geophysical data for uranium‐mineralized breccia pipes exploration in northwestern Arizona

Digital image processing and integration of data sets have been used to develop exploration models from airborne electromagnetics (EM), magnetics, and very‐low‐frequency electromagnetics (VLF-EM) data collected over an area in northwestern Arizona. The area has potential for the occurrence of uranium‐mineralized breccia pipes. Apparent resistivity and overburden thickness were derived from the EM measurements using half‐space models. Digital image processing techniques applied to the geophysical data sets included: (1) conversion of the data into gridded‐scale images, (2) spatial filtering for noise removal, (3) integration and analysis of the data sets, and (4) modeling using various parameter combinations. The general relationships between the geophysical variables/parameters and their ability to detect metallic deposits were used as guides in selecting digital number ranges that were used as input into various models. One of the best models incorporated apparent resistivity and total‐field magnetics; t...