Laser Technology UltraLyte, Руководство пользователя

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Electronic Copy of LTI’s UltraLyte User’s Manual – 7 th Edition June 1998
23
Measured Speed by Angle: The Cosine Effect
Angle True Speed
(degrees) 30 mph 40 mph 50 mph 60 mph 70 mph
Measured Speed (mph)
0 30.00 40.00 50.00 60.00 70.00
1 29.99 39.99 49.99 59.99 69.99
3 29.96 39.94 49.93 59.92 69.90
5 29.89 39.85 49.81 59.77 69.73
10 29.54 39.39 49.24 59.09 68.94
15 28.98 38.64 48.30 57.94 67.61
20 28.19 37.59 46.99 56.38 65.78
45 21.21 28.28 35.36 42.43 49.50
90 00.00 00.00 00.00 00.00 00.00
The cosine effect decreases as the range to the
target vehicle increases. At the maximum range of
the instrument, the vehicle is so far away that the
angle between it and the instrument is very small
indeed, and the instrument’s perception of the
target's speed is identical to its true speed. As the
vehicle approaches, however, the angle increases
until it becomes large enough to affect the
measurement.
To minimize the cosine effect, keep the angle small
by setting up the instrument as close to the road as
possible without creating safety risks, and target
down the road at ranges sufficient to keep the
angular difference small.
The following chart shows acceptable parameters
for minimizing the cosine effect. The chart indicates
the percentage of true speed measured, given the
distance from the roadway and the distance from the
target vehicle. To find a target's measured speed,
multiply the true speed by the number in the chart.
For Internal Use Only. Not for Distribution.