When resecting or fixing a position, the geometric strength (angular disparity) of the mapped points affects the precision and accuracy of the outcome. In navigation įor broader coverage of this topic, see Position fixing. Two or more bearings to mapped, known points are taken their resultant lines of position drawn from those points to where they intersect will reveal the navigator's location. Resection simply reverses the intersection process by using crossed back bearings, where the navigator's position is the unknown. The reverse of the intersection technique is appropriately termed resection. In earlier times, the intersection method was used by forest agencies and others using specialized alidades to plot the (unknown) location of an observed forest fire from two or more mapped (known) locations, such as forest fire observer towers. The target is located where the lines intersect on the map. At each known point (hill, lighthouse, etc.), the navigator measures the bearing to the same unmapped target, drawing a line on the map from each known position to the target. When intersecting, lines of position are used to fix the position of an unmapped feature or point by fixing its position relative to two (or more) mapped or known points, the method is known as intersection. Both methods involve taking azimuths or bearings to two or more objects, then drawing lines of position along those recorded bearings or azimuths. Resection and its related method, intersection, are used in surveying as well as in general land navigation (including inshore marine navigation using shore-based landmarks).
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