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To compute the greatest distance D BL at which an observer B can see the top of an object L above the horizon, simply add the distances to the horizon from each of the two points: D BL = D B + D L For example, for an observer B with a height of h B =1.70 m standing on the ground, the horizon is D B =4.65 km away.
Low levels can be caused by at least three basic reasons: low transmit level, for example Wi-Fi power levels; far-away transmitter, such as 3G more than 5 miles (8.0 km) away or TV more than 31 miles (50 km) away; and obstruction between the transmitter and the receiver, leaving no clear path. NLOS lowers the effective received power.
The presence of objects not in the direct line-of-sight can cause diffraction effects that disrupt radio transmissions. For the best propagation, a volume known as the first Fresnel zone should be free of obstructions. Reflected radiation from the surface of the surrounding ground or salt water can also either cancel out or enhance the direct ...
The standard measurement for underwater visibility is the distance at which a Secchi disc can be seen. The range of underwater vision is usually limited by turbidity. In very clear water visibility may extend as far as about 80m, [18] and a record Secchi depth of 79 m has been reported from a coastal polynya of the Eastern Weddell Sea ...
At around 600 miles wide and up to 6,000 meters (nearly four miles) deep, the Drake is objectively a vast body of water. To us, that is. To the planet as a whole, less so.
This edition focuses on what you’d see if you traveled far enough into the future to watch the universe end. Luckily for us Matt Caplan, a theoretical physicist from Illinois State University ...
The first patent for a system designed to use continuous-wave radar to locate buried objects was submitted by Gotthelf Leimbach and Heinrich Löwy in 1910, six years after the first patent for radar itself (patent DE 237 944).
Pulse-Doppler radar can reduce clutter by over 60 dB, which can allow objects smaller than 1-square-foot (0.093 m 2) to be detected without overloading computers and users. Systems using pulse-Doppler signal processing with speed rejection set above the wind speed have no clutter zone.