Suunto Tandem manual 100

When calculating the hori-
zontal distance	by using
the ground distance and
the slope angle, it must be
pointed out that an error is				29%
introduced if the slope		is	24.7 m [81 ft]		1.6 m
measured from eye level to			23%	9%
					[5½ ft]
the pillar base. Measuring			1.6 m
the slope along the ground
			[5½ ft]
would be cumbersome and
inconvenient. No error		is
introduced, however, when			Fig. 11. Calculating horizontal distance by using
the slope angle is mea-			ground distance and slope angle
sured from eye level to a
sighting mark	made	or

placed on the pillar at eye level (Fig. 11) whereby the two lines of measurement become parallel. The true angle of slope is 9 degrees. The example shown in Fig. 11 illustrates both methods of calculation.

Method 1. Measure the ground distance. This is found to be 25 m [82 ft]. Then measure the slope angle. This is 9 degrees. Read percentages of top and ground points. These are 29 and 23 per cent.

Calculate:
23	29	52
--------	+ --------=	--------
100	100	100

16