[1] It describes a variety of techniques used for finding moving objects, like an aircraft, and filter out unmoving ones, like hills or trees.These were subject to a wide variety of noise effects that made them useful only for strong signals, generally for aircraft or ship detection.This technique is far more resistant to noise, and can easily be tuned to select different velocity thresholds to filter out different types of motion.The MTI radar uses low pulse repetition frequency (PRF) to avoid range ambiguities.Phase jitter, Doppler effects, and environmental influences limit MTI sub-clutter visibility Measure of Performance to about 25 dB improvement.The probability of detecting a given target at a given range any time the radar beam scans across it, Pd is determined by factors that include the size of the antenna and the amount of power it radiates.To capture most of this traffic, even when it is moving almost tangentially through the radar (i.e., perpendicular to the radar-target line), a system must have the ability to detect very slow radial velocities.This is calculated as:[citation needed] Any target with a velocity less than this minimum (MDV) cannot be detected because there is not sufficient Doppler shift in its echo to separate it from the mainlobe clutter return.Other factors which may be relevant include grid spacing, size of the power amplifier, module quantization, the number of beams processed and system losses.The earth's curvature and screening from terrain, foliage, and buildings cause system altitude to be another key factor determining depth of coverage.Frequent revisits are very important to the radar's ability to achieve track continuity and contribute to an increased probability of target detection by lessening the chance of obscuration from screening by trees, buildings, or other objects.A fast revisit rate becomes critical to providing an uncorrupted track when a target moves in dense traffic or is temporarily obscured, if only by trees along a road.
