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presentation to CMLRD (now DRMS) within one year following cessation of subsidence. This reporting <br />will no longer be required. <br />The following is a description of the various phases of the subsidence monitoring program. <br />(1) Ground Survey Eight control monuments were established outside the zone of subsidence <br />to provide horizontal and vertical control for the area. Before each flight, the monuments were paneled <br />and re- leveled to determine their elevations by differential leveling or by using reciprocal vertical angles. <br />Panels had three or four arms, each 3 feet by 9 inches in size. Nine other points were established <br />outside the zone of subsidence and re- leveled prior to each flight to provide additional vertical control. <br />Map 131 shows the predicted subsidence contours and the 17 control points outside the zone of <br />subsidence. <br />Five additional control points were established inside the zone of subsidence. Three were established <br />along the axis of LW-1 and two were established over RP -5. These are also shown on Map 131. The <br />five monuments within the zones of subsidence were surveyed at the same time as the 17 control <br />points. Thereafter, the three "inside" monuments were surveyed every six months until the subsidence <br />was determined to have ceased. Semi - annual surveys of the "inside" monuments allowed BME to <br />determine when subsidence was complete. However, subsidence will probably continue for many <br />years over RP -1. The elevations determined by the aerial monitoring techniques can also be compared <br />to those generated by on- the - ground surveying. <br />(2) Aerial Photoaraphv Photography was taken at a scale of 1" =275' using black and white <br />film with a precise camera of 6 -inch focal length. <br />(3) Analytical Aerial Trianaulation This process was required to densify and check the <br />ground control, using sophisticated simultaneous least square bundle adjustment software. <br />(4) Measurement of Reaular Grid Dialtal Terrain Model (DTM) This was done using a highly <br />precise analytical stereoplotter. A grid boundary with grids oriented to the mining panels, was defined, <br />and the plotter driven automatically to X, Y (Easting, Northing) coordinates at exactly 100' grid intervals <br />by a computer. At each point the stereo - operator placed the measuring mark precisely on the ground, <br />after which the elevation was automatically recorded and stored together with the X, Y coordinates of <br />the point. Approximately 2800 points per square mile were measured. <br />BME proposed to determine elevations twice for the first set of photography. A comparison of the two <br />data sets were made so any significant discrepancies could be eliminated. This improved the accuracy <br />of the baseline data. <br />Permit Renewal #6 (04/2014) III -23 <br />