StreamPro ADCP Operation Manual - global site

StreamPro ADCP Operation Manual------ G ------Gimbals: Frame that will support the weight of an object but allow its freerotation. Gimbals can be constructed to allow free rotation in one, two, orthree axes.Gyro: A rapidly spinning device mounted on gimbals to maintain a constantorientation. These devices are commonly used to measure heading on shipsbecause, unlike magnetic compasses, they are unaffected by ferrous metalsor by varying electromagnetic fields. They can also be used to measurepitch and roll because, unlike liquid level sensors, they are unaffected byaccelerations.------ H ------Homogeneity: The extent to which the current measured by all four beamsis the same. A key assumption of all ADCP processing is that the currentsare horizontally homogeneous across the four beams. This assumption ischecked for each measurement by using the error velocity measurement.Horizontal ADCP (H-ADCP): Instrument designed to measure velocityprofiles in a horizontal plane.------ I ------Inertial Navigation: Method for estimating the attitude and position of amoving platform (of primary interest here are AUVs) by integrating measurementsfrom gyros and accelerometers. This integration is subject tolarge errors over time, so DVLs and pressure sensors are commonly incorporatedas external inputs to measure and correct these errors.------ J ------------ K ------------ L ------Lag: A time delay between pulses or pings.Long Ranger: Model name for Workhorse ADCPs of frequency 75 kHz.Lowered ADCP (L-ADCP): Technique whereby one or two ADCPs arelowered through the water column (typically on a rosette) to obtain velocityprofiles over the full ocean depth. Note that a whole body of research existson how to properly remove the motion of the rosette from the velocitymeasurements obtained in this manner.page 104Teledyne RD Instruments