Suunto 1520, PM5 manual Nomographical Height Correction

NOMOGRAPHICAL HEIGHT CORRECTION

When the nomogram is used, all correction calculation becomes unnecessary. Only a ruler or some other convenient object with a straight edge is needed to obtain the nomographical solution. The nomogram is used by placing the ruler so that its edge intersects the angle scale on the left at the slope angle point and the observed height scale (on the right) at the pertinent point. The corrected height (or distance) is read at the point where the edge intersects the corrected height scale in the middle. When using a measuring distance of 100 m / ft. along the ground the correction procedure becomes very simple. No slope angle measurement is then necessary. One needs only the reading of the top point and that of the ground point. Depending on the situation their sum or difference gives the apparent height directly in feet. This is then corrected as follows: First, find on the right-hand scale in the nomogram the point indicating the apparent height. Secondly find on the left-hand double scale the point indicating the ground point reading. Thirdly, connect these points. The corrected reading will be found from the pertinent middle scale at the point of intersection. In this procedure the slope angle can be neglected as the left-hand ground point scale has been constructed so that slope angle and the average eye level height of 1.6 m / 5.5 ft. have been taken into account.

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