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Transcription
STADIA REDUCTION
DIAGRAM
Enter on the horizontal scale with
the value of the stadia reading (the
interval times the stadia constant)
and run vertically upward to inter-section with line representing
the vertical angle. The location
of this point with reference to
the dotted lines marked
"ONE" etc., gives the correction
to be subtracted from the entering value, and to which "f + c"
(usually about 1 foot) must be
added to obtain the true
horizontal distance. The
reading on the vertical
scale plus about 0.1 ft.
for each 5° of vertical angle (f + c) sin α] is the true vertical dis-tance.
If the vertical angle
is beyond the range of
diagram, use
H = R cos²α + 1 to find true horizontal distance and
V = R × ½ sin 2α for true vertical distance,
where R equals observed stadia distance and α equals vertical angle.
300
90
85
80
75
70
65
60
55
50
45
40
35
30
25
20
15
10
5
0
90
85
80
75
70
65
60
55
50
45
40
35
30
25
20
15
10
5
VERTICAL DISTANCE
STADIA READING X STADIA CONSTANT
14