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Atmosphere
Published in Mohammad H. Sadraey, Aircraft Performance, 2017
An altimeter is an active instrument used to measure the altitude of an object above a fixed level. The three main types of altimeters are (1) Pressure altimeter, or aneroid barometer, which approximates altitude above sea level by measuring atmospheric pressure; (2) Radio or radar altimeter, which measures absolute altitude (distance above land or water) based on the time required for a signal; (3) GPS, which uses the satellite constellation and is fairly accurate.
Air Traffic Control System
Published in Milica Kalić, Slavica Dožić, Danica Babić, Introduction to the Air Transport System, 2022
Milica Kalić, Slavica Dožić, Danica Babić
An altimeter is an instrument used to measure the altitude of an object above a fixed level. It measures ambient air pressure, which decreases with increasing altitude (approximately 100 hPa at 800 m, i.e., 1 mmHg of column at 1,000 ft above sea level). The altimeter then calculates and displays the corresponding altitude. It is essentially a calibrated barometer that displays an altitude—a barometric altimeter.
Retarded state-multiplicative stochastic systems - Robust H ∞ and H 2 vertex-dependent filtering
Published in International Journal of Control, 2022
In order to demonstrate the application of the our theory to practical control engineering, we consider the problem of altitude estimation with measurements from a RADAR altimeter and a baro altimeter (Gershon et al., 2005). We bring a short description of the problem at hand for convenience. The barometric altitude measurement is based on a static pressure measurement. As a result of various sources of error, (e.g. initial reference error, static pressure measurement bias, or temperature measurement errors) the baro altimeter is corrupted with a bias error (see Chapter 11, Gershon et al., 2005) up to 1000 ft together with a small white noise component. Denoting the true altitude above ground by h, we have the following approximate model for the altitude hold loop which is commanded by the altitude command where is the time constant of the command response, b represents the baro altitude measurement bias and is a standard zero-mean white noise with intensity , that is: The RADAR altimeter measures the height above ground level without bias, however, its output is corrupted by a broad band measurement noise, the intensity of which increases with height due to a lower SNR (signal to noise ratio) effect at higher altitude.
Applied geophysics for cover thickness mapping in the southern Thomson Orogen
Published in Australian Journal of Earth Sciences, 2018
I. C. Roach, C. B. Folkes, J. Goodwin, J. Holzschuh, W. Jiang, A. A. McPherson, A. J. Meixner
Both methods were performed on high quality regional airborne magnetic line-data acquired with flight-line spacings of 400 m or less, detailed in Table 1. Flight-line data are preferred over the derivative gridded data for two reasons. First, flight-line data are usually recorded with a radar altimeter channel so that the aircraft height above ground is known. The actual aircraft height may vary by tens of metres from the nominal flight height, leading to significant uncertainty in the depth estimates from gridded data. Second, the sample spacing along the lines (»7 m) is less than the cell size of the derivative grids (generally 80 m for a survey acquired at 400 m flight-line spacing). The closely spaced sampling along flight-line data ensures that the highest frequency anomalies from magnetic sources at the surface are adequately sampled, meaning that there is no loss of depth resolution that may occur for the same magnetic sources from the gridded data.
Bluelink ocean forecasting Australia: 15 years of operational ocean service delivery with societal, economic and environmental benefits
Published in Journal of Operational Oceanography, 2020
Andreas Schiller, Gary B. Brassington, Peter Oke, Madeleine Cahill, Prasanth Divakaran, Mikhail Entel, Justin Freeman, David Griffin, Mike Herzfeld, Ron Hoeke, Xinmei Huang, Emlyn Jones, Edward King, Barbra Parker, Tracey Pitman, Uwe Rosebrock, Jessica Sweeney, Andy Taylor, Marcus Thatcher, Robert Woodham, Aihong Zhong
At present, satellite altimetry data is retrieved from the RADAR Altimeter Database System (RADS; Scharroo 2012), which was developed by the Delft Institute for Earth-Oriented Space Research and the NOAA Laboratory for Satellite Altimetry. This has significantly improved the efficiency of product implementation compared to multiple sources used previously. Altimetry tracks are carefully checked, using a system developed by CSIRO, at the BoM prior to use in ocean data assimilation. New satellite SST data are regularly introduced into BRAN and OceanMAPS to improve forecasts and replace decommissioned instruments. The specific platforms implemented operationally in OceanMAPS are summarised in Table 1.