, OH
The Ohio Standard Baseline (OSB) was a geodetic baseline that provided highly accurate measurements of the earth and made possible extremely fine calibrations of surveying equipment. Several such baselines were established in Europe and South America during the mid-twentieth century, specifically designed to use a measurement device called the Vaisala Comparator, a precursor of modern laser light measurement systems. In 1953, Dr. T.J. Kukkamaki, then a professor in the Department of Geodetic Science at The Ohio State University, proposed establishing a baseline in Ohio that would be part of the worldwide efforts to accurately understand how the size and shape of the earth change over time. Built between 1965 and 1966, the resulting OSB consisted of a series of eight concrete pillars supporting mirrors and instruments, spaced along a 500 meter distance. (Continued on other side)
, OH
In 1883, James E. Brown built this seven-panel Howe truss bridge over the North Branch of Caesar Creek, near the site of Lyman Ballard’s grist mill and on the property of William C. Dean. At the time it was built, iron, concrete, and steel structures began to surpass the construction of wooden covered bridges. The construction of U.S. Route 35 severed the bridge from its original connection to the Dean property. In 1975, the bridge was added to the National Register of Historic Places. As of 2016, the Ballard Road bridge is one of six covered bridges in Greene County.
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