http://www.loc.gov/mods/v3 http://www.loc.gov/standards/mods/v3/mods-3-2.xsd
A fiber optic system for measuring magnetic heading and pitch of one or more compass heads in a towed acoustic array has been developed as a cooperative effort between engineers at Fiber Dynamics, Inc., and faculty and graduate students at Texas A&M. An unconventional photolithographic process for producing a bar-code pattern on a curved (spherical) surface was successfully implemented. First, an absorption process for applying a thin layer of photoresist uniformly to the gold-coated surface of a glass sphere was perfected. Then, a system for defining the patterns in the metal was assembled. A LabView computer program controlled the system as required to define the bar code pattern in the metal. High-quality bar code patterns were produced on floating spheres by this method. The data acquisition/signal processing system digitized and processed the raw data returning from the compass heads, and computed magnetic heading and pitch from the data. Processing of the signal from a single compass head required readout of a 7-bit binary code giving coarse heading, using timing information to obtain fine heading, and measuring the apparent width of an analog bar to determine pitch. When monitoring multiple compass heads distributed along the fiber, a time-division demultiplexing technique was used for separating the data from the individual compass heads. For testing the system, the cylindrical sensor head was mounted on a machinist's table for rotating it through 360° in the horizontal plane to vary the heading, and through ±10° about a horizontal axis to vary pitch. Measured resolutions of the system were 0.044° for heading, and 0.85° for pitch.
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