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CORRECTING FOR SLOPE. When
you take a measurement with a tape along an inclined plane (along the natural slope of the ground),
obviously, the taped distance is greater than the horizontal distance. This taped distance is
represented by s in figure 12-15. The difference between the slope distance and the horizontal distance (s d) is called the slope correction. This correction is always subtracted from the slope distance. To compute for the slope correction, you should know either the vertical
Figure 12-15.-Correction for slope distance. angle, A, or the difference in elevation h between the taped stations. When the vertical angle is used, the formula for slope correction is as follows:
When the difference in elevation is used, the approximate formula derived by Pythagorean theorem of a right triangle (fig. 12-15) for the slope correction is as follows:
But for a small slope, d is approximately equal to s; therefore,
For slopes greater than 5 percent, a closer approximation of Ch can be determined by expanding the above formula to this form.
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