The solid outcrop line indicates where the bed has been mapped with assurance as to its intersection with the ground surface; the dashed line indicates uncertainty as to the exact location.
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Figure 9 illustrates how to determine areas of reliability (areas based on distance of from points of thickness measurements-- measured, indicated, inferred, and hypothetical coal) where a coal bed has been mapped on the surface and the thickness of coal has been measured at five points. The solid outcrop line indicates where the bed has been mapped with assurance as to its intersection with the ground surface; the dashed line indicates uncertainty as to the exact location. Utilizing radii originating at the points of thickness measurements, arcs are constructed at appropriate distances according to the criteria for the measured, indicated, inferred, and hypothetical reliability categories. The arcs enclose areas theoretically underlain by coal for each reliability category.

Figure 10 uses the same coal bed outcrop as figure 9 and shows the effect of additional thickness information from drill-hole measurements and a small mine. A comparison of figures 9 and 10 illustrates how the additional data derived from drill-holes and mining expand the areas designated in figure 10 as measured and indicated and modify the inferred and hypothetical areas.

中国矿业大学采矿工程系的林老师告诉记者，地质图上煤层分布、岩石构造、水文情况都标示得十分清楚，每个小窑主都会在决定开采时采取措施趋利避害。