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vertical angles. Panels had three or four arms, each 3 feet by 9 inches in size. Nine other points were <br />established outside the zone of subsidence and re-levelled prior to each flight to provide additional <br />vertical control. Map 131 shows the predicted subsidence contours and the 17 control points outside <br />the zone of 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 <br />compared to those generated by on-the-ground surveying. <br />(2) Aerial Photograahv 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 Triangulation This process was required to density and check the <br />ground control, using sophisticated simultaneous least square bundle adjustment software. <br />• (4) Measurement of Regular Grid Digital 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 (Fasting, 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 <br />accuracy of the baseline data. <br />After a subsequent flight and re-measurement, the amount of subsidence was calculated from the <br />difference in elevation at each point which had the same X, Y coordinates. <br />(5) Topographic Base Maa From the original DTM data with additional "breaktines" such as <br />drains and ridges digitized in the analytical plotter, a contour map at a 5 foot contour interval was <br />plotted at 1"=200' scale, with the contours being generated automatically from the digitized X, Y, Z <br />points. Contours within Red Wash valley were plotted at one foot intervals so that gradient changes <br />• Permit Renewal #3 (Rev, 8/99) III-24 <br />