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~~~'~.' <br />• At the present time 1t is planned to only survey ling points before <br />subsidence commences and after subsidence has ceased. <br />The subsidence/strain monuments will be intensively surveyed throughout <br />the subsidence cycle. The frequency of surveying will vary from semi- <br />annually for monuments more than 2000 ft. from the mining face to two <br />times a week for actively subsiding points. After subsidence has nearly <br />stopped. surveying will be reduced to bi-weekly monthly and flnatly. <br />semi-annually. <br />Actual surveying will be performed with a M11d T-2 one-second theodolite <br />and a Mild/Sercel distomat. Each survey of a monument will consist of a <br />slope distance measurement an inverted and erect vertical angle <br />• measurement and an inverted and erect horizontal angle measurement. <br />Data Processing <br />The survey data for a point M111 be reduced to provide coordinates and <br />elevations_of the subsidence monument. Values obtained from each survey <br />will be compared to the baseline values obtained before subsidence <br />began. All calculations will be performed with programmable calculators <br />and computers. <br /> <br />31 <br />