Technology of LADS - Laser Airborne Depth Sounder :: essays research papers

An aeroplane flies about 400-500 metres above the water at a speed of approximately 60 - 70 m/s. Then the aircraft will send out a pulse which is moderately reflected off the surface of the water and moderately broadcasted into the water and reflected off the oceans floor, as a result two pulses are sent back to the aircraft. The pulse which was reflected of the surface of the water is a red beam (infrared) which measures the aircraft height above the water and is directed vertically downward. The beam which reflects off the seabed is a green colour and is examined over a semicircle of +/ -15 degrees to the planes bearing and pulsates at approx 160 pulses per second. The aircrafts equipment will record the speed of the wave and the travel time during air to calculate depth . Therefore LADS must be flown during hours of darkness to eliminate the errors caused by the reflection of the sun off the water, which return false reading to the aircraft causing inaccurate depth. The calculate the green beam (which travels to the seabed and back up) you must obtain the speed of light in water which is given by Maxwell?s equations which basically show that When passing through a transparent or translucent material medium, like glass or air, light will have a slower speed than in a vacuum . Therefore the extra time and distance traveled by the green pulse can be calculated, giving the depth of the water. The aircraft needs to use two beams to ensure that the pulses return to the aircraft. In certain situations the pulse may not return to the aircraft due to flat glassy water surface (because of the law of reflection) . The Lads software automatically compiles arrival times and fixes errors in the data like tidal variations. Maps can be made after data is compiled from the aircraft by using Global Positioning Satellites, which constructs coordinates and data collected. The green laser is used due to its incorporation of light in murky waters is the slightest at these wavelengths. One laser is applies which creates an infrared laser. A frequency double then changes the frequency of a fraction of the beam by a aspect of two , resulting in a green light laser. Some Advantages and Disadvantages of LADS include: Advantages Disadvantages ? A quick and effortless way of measuring depth of waters. ? Can compile its data and send it to satellites, which create map images.