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The design sight distance allows a below-average driver to stop in time to avoid a collision in most cases. Driver perception/reaction distance is calculated by: d PRT = 0.278 Vt (metric) d PRT = 1.47 Vt (US customary) Where: d PRT = driver perception-reaction distance, m (ft) V = design speed, km/h (mph) t = brake reaction time, in seconds
See also Non-line-of-sight propagation for more on impairments in propagation. It is important to take into account the curvature of the Earth for calculation of line-of-sight paths from maps, when a direct visual fix cannot be made. Designs for microwave formerly used 4 ⁄ 3 Earth radius to compute clearances along the path.
In practice it is not necessary to use zenith distances, which are 90° minus altitude, as the calculations can be done using observed altitude and calculated altitude. Taking a sight using the intercept method consists of the following process: Observe the altitude above the horizon Ho of a celestial body and note the time of the observation.
Sight distance, in the context of road design, is defined as "the length of roadway ahead visible to the driver".[1] Sight distance is how far a road user (usually a vehicle driver) can see before the line of sight is blocked by a hill crest, or an obstacle on the inside of a horizontal curve or intersection.
Soldier observed at 400 m: The stadiametric rangefinder in the bottom-left corner of the PSO-1 telescopic sight reticle can be used to determine the distance from a 1.70-meter (5 ft 7 in) tall person or object from 200 m (bracket number 2 to the right) to 1,000 m (bracket number 10 to the left).
Sight is defined as the observation of the altitude, and sometimes also the azimuth, of a celestial body for a line of position; or the data obtained by such observation. [1] The mathematical basis of sight reduction is the circle of equal altitude. The calculation can be done by computer, or by hand via tabular methods and longhand methods.
With this calculation, the horizon for a radar at a 1-mile (1.6 km) altitude is 89-mile (143 km). The radar horizon with an antenna height of 75 feet (23 m) over the ocean is 10-mile (16 km). However, since the pressure and water vapor content of the atmosphere varies with height, the path used by the radar beam is refracted by the change in ...
b) the greatest distance at which lights of 1,000 candelas can be seen and identified against an unlit background. Note.— The two distances have different values in air of a given extinction coefficient, and the latter b) varies with the background illumination. The former a) is represented by the meteorological optical range (MOR).