Geoscience Reference
In-Depth Information
L
W
FIGURE 2.4
Rectangle.
Chaining uses a surveyor's chain or tape of known length. Stakes are placed at each end of the
tape. The stakes are used to set or locate the starting point for each progressive measurement and to
maintain an exact count of the number of times the tape was moved. Sight down the stakes to keep
the measurement in a straight line. The number of times the tape is moved multiplied by the length
of the tape equals the total distance.
Pacing uses the average distance of a person's pace or stride. To determine your pace length,
measure a 100-foot distance and pace it, counting the number of strides. Pace in a comfortable and
natural manner. Repeat the procedure several times and get an average distance for your stride. It is
good practice to always pace a distance more than once and average the number of paces (Masser
and Jennings, 1991). The formula for calculating distances from pacing is
Distance (ft) = Total number of paces × Length of average pace
A rectangle is a two-dimensional box. The area of a rectangle is found by multiplying the length
( L ) times width ( W ) (see Figure 2.4).
Area = L × W
(2.6)
EXAMPLE 2.46
Problem: Find the area of the rectangle shown in Figure 2.5.
Solution:
Area = L × W = 14 ft × 6 ft = 84 ft 2
To find the area of a circle, we need to introduce a new term, the radius , which is represented
by r . The circle shown in Figure 2.6 has a radius of 6 ft. The radius is any straight line that radiates
from the center of the circle to some point on the circumference. By definition, all radii (plural of
radius) of the same circle are equal. The surface area of a circle is determined by multiplying π
times the radius squared:
A = π × r 2
(2.7)
14 ft
6 ft
6 ft
14 ft
FIGURE 2.5
Area of a rectangle for Example 2.46.
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