B
ASIC
S
PEED
M
EASUREMENT
Electronic Copy of LTI’s UltraLyte User’s Manual – 7
th
Edition June 1998
22
It means one of two things: either you are targeting a
strong light source such as headlights, or a targeted
vehicle is employing a laser jamming device.
Regardless of the level of interference, you will
never get an erroneous speed reading. At a low
level of interference, you will get a good speed
reading, even though the jam tone sounds and the
indicator blinks. At a high level of interference, you
will get an E06 error condition.
Line of Sight
You must at all times have a clear line of sight to the
target vehicle. If an object intersects the beam while
a velocity measurement is being taken, an error
message displays.
The Cosine Effect
If a target vehicle is moving directly toward or away
from you, the velocity measured by the UltraLyte is
identical to the vehicle’s true speed.
For safety, however, the instrument is usually set up
on the side of the road, resulting in an angle
between the instrument’s position and the target
vehicle's direction of travel. When the angle is
significant, the measured speed is less than the
target's true speed. The phenomenon is known as
the “cosine effect.” (“Cosine” is a trigonometric
function related to the phenomenon.)
The difference between the measured speed and
the true speed depends upon the angle between the
instrument’s
ideal
position— the position where
targets would be moving in direct line with the
instrument—and its
actual
position. The larger the
angle, the lower the measured speed. The effect
always works to the motorist's advantage.
Loosely speaking, the cosine effect is not significant
as long as the angle remains small. The following
table shows the effect:
For Internal Use Only. Not for Distribution.
Summary of Contents for UltraLyte
Page 1: ...For Internal Use Only Not for Distribution...
Page 70: ......
