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TARGET SPEED ACQUISITION
A target can be anything that is moving. To acquire the speed of a target, with the Speedster
powered on, aim the Speedster at the target and depress the TRIGGER. The RADAR ACTIVE
icon will appear in the upper right corner of the LCD display. This indicates the Doppler Radar
is functioning. The speed of the target will appear on the LCD display. When the speed appears,
release the trigger so that the speed displayed will "lock" on the display for easy viewing.The units
of measure will appear at the top of the LCD screen and can be changed from MPH to KPH, or
vice versa via the SETUP screen.
The Bushnell Speedster is capable of tracking Last and Average speeds.
Speedster to record and track Last and Average speeds, simply press the ENTER button after
every speed measurement is locked onto the LCD display. A speed is locked onto the LCD
display after the release of the TRIGGER. The Speedster will automatically save this data for
later use to internal memory while in the "SPEED + BASEBALL STATS" Mode. Data captured
in the "SPEED" only mode can not be saved to internal memory.
There are certain mathematical properties of Doppler Radar that affect the accuracy of your
Bushnell Speedster. Please read COSINE AFFECT ON TARGET VELOCITY below. As a
quick reference to accuracy, remember to keep your targets direction of travel in a direct line with
you, and not perpendicular.
COSINE EFFECT ON TARGET VELOCITY
The Speedster will measure the relative speed of a target as it approaches the Speedster. If the
target is in a direct line (collision course) with the Speedster the measured speed will be exact. As
the angle of incidence increases, if you move either right or left of this direct line, the accuracy
will decrease.
The measured speed will decrease as you move off this centerline. This
phenomenon is called the Cosine Effect. It is so called because the measured speed is directly
related to the cosine of the angle between the Speedster and the target's direction of travel. Figure
9 below relates this to a little league baseball field.
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Table 1 below gives calculated distances for the Figure 9 above.
Total distance
Pitcher to seats
If you desire for the
According to the table, assuming the average distance from the pitcher to catcher (y) is 60 feet, there
will also be an average distance behind the catcher to the seats (y1). This is assumed to be an average
of 20 feet. So the total distance from pitcher to Speedster (ytot) is 80 feet for this example. This is the
straight-line direction of ball travel, not the distance from the pitcher to the actual Speedster position,
which is R.
If you sit at a distance of 14 ft. off center of the direct pitcher to catcher line, then you have an angle
of incidence of 10°. Most importantly, this gives you an error of 1.5% in measured speed, which is
acceptable. Following the chart across, if you sit 29 ft. off center this correlates to a 20° angle and a
6% error. See the Measured Speed vs Angle chart for more information on error percentage.
As noted earlier, the larger the angle of incidence the greater the error in the measured speed. Figure
10 below indicates the percent error vs. the angle of incidence.
The graph indicates that at an angle of 0° (direct line) there is no error. If there is an angle of 10° the
error is about 1.5%, for a 20° angle it is about 6% and for a 30° angle the error is about 13%, probably
unacceptable for baseball pitches.
Distance off center (x)
Distance off center (x)
at a 10° angle
(ytot)
(gives a 1.5% error)
30
5 ft.
40
7 ft.
50
8 ft.
60
10 ft.
70
12 ft.
80
14 ft.
90
15 ft.
100
17 ft.
Measured Speed vs Angle (% of actual speed)
100
90
80
70
60
50
40
30
20
10
0
0
10
20
30
40
Angle of Incidence
Angle of Incidence
Distance off center (x)
at a 20° angle
at a 30° angle
(gives a 6% error)
(gives a 13% error)
10 ft.
17 ft.
14 ft.
23 ft.
18 ft.
28 ft.
21 ft.
34 ft.
25 ft.
40 ft.
29 ft.
46 ft.
32 ft.
51 ft.
36 ft.
57 ft.
50
60
70
80
90
100
(Figure 10)
Table 1
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