This situation occurs enough to have a name - Patrol Speed Shadowing. This occurs when the radar measures ground reflections off angle, causing the radar measured patrol speed to measure low by the cosine of the angle, and target speed to compute high. The radar should be located as close to the road as practical to minimize cosine effect errors and limitations.Ī radar in moving mode can measure target speed high in some situations due to the Cosine Effect. When speed drops too fast the radar/lidar loses track and the target is in the radar's Blind Zone. As a target approaches a radar the Cosine Angle gets larger, and gets larger faster. The larger the angle the lower the measured speed.
The angle is referred to as the Cosine Effect angle because measured speed is directly proportional to the cosine of this angle. The angle between the radar or lidar and target must be small for an accurate speed measurement. A radar may track a distant large vehicle instead of a closer small vehicle without any indication to the operator which vehicle the radar is tracking. Detection range can be as low as 100 feet or less to over a mile. Target size, shape, and reflectivity effect radar detection range. Larger targets will be detected at longer ranges, usually. Target detection range depends on radar frequency and power, angle to target, antenna factors, and weather. Microwave radar radiates a cone shaped beam that has a relatively wide beam, 9° to 25°, that easily covers several lanes of traffic at a relatively short range.īeamwidth Spread Distance Calculate or Re-calculate
Measures 2 targets, fastest and strongest.Moving mode measures on-coming traffic.The strongest target reflection is usually the closest, but not always.All radars have an audio tone that indicates direction. Some, but not all, radars indicate traffic direction ("+" for approaching and "-" for receding traffic). Some radars measure approaching and receding traffic at the same time.Moving mode radars come with a patrol car mount for moving mode operation.Measures 2 targets, fastest and strongest (3).Police radars are available in 2 basic configurations, hand-held or fix mounted. Typically multiple sample periods are required when an echo is first detected, longer range targets, or if the radar has just started transmitting. The radars must dwell (sample period) on a target about a quarter to a third of a second to get one speed reading.
The reflections are frequency shifted by the Doppler Effect and proportional to speed. Police microwave Doppler radar transmits while simultaneously receiving reflections from moving objects. ( 2) a remote sensor that emits electromagnetic radio waves, microwaves, or infrared laser light in order to measure reflections for detection purposes such as presence, location, motion, speed. ( 1) acronym for RAdio Detection And Ranging. Moving mode radar is accurate to ± 2 MPH.
Max track doppler plus#
Radar and lidar are accurate to plus or minus 1 mile per hour (± 1 MPH). Lidar is also referred to as Laser Radar. Radars use microwaves, and lidar uses pulsed infrared (IR) laser light radiation, to measure target reflections to determine speed. The most common police speed measuring devices are radar and lidar. Acceleration Parameters Constants / Conversions Police 10 Codes Universal Time (UTC) Links Blog Home |
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