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Topic: Altimetry

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	Operational Satellite Altimetry (Site not responding. Last check: 2007-10-15)
		Due to its global coverage the altimetry has provided information about the sea level and its spatial as well as temporal variability that previously could not be obtained from coastal tide gauges alone.
		In near-real time applications of sea level information the role of satellite altimetry is limited by the fact that measurements from about one week is needed to recover the regional pattern of the "current" sea level.
		Furthermore, the GDR altimetry from different satellite mission may have been processed using different strategies and, by time, the GDR data may be further developed when new information become available.
	research.kms.dk /~pk/cost.html (989 words)

	Cnes - Altimetry theory
		Altimetry measurements are acquired by an altimeter on a non-synchronous satellite in a repeating low-Earth orbit designed to fly over the same points at regular intervals.
		In practice, to achieve the required level of accuracy, this theoretical measurement is corrected for perturbations of the satellite on its orbit and propagation of radio waves as they pass through the atmosphere.
		The orbit of an altimetry satellite is a compromise: the shorter the orbital period, and therefore the revisit interval, the narrower the coverage area.
	www.cnes.fr /html/_455_456_1088_1090_.php (306 words)

	JPL.NASA.GOV: Feature Stories
		Scientists were quick to use altimetry data for studies ranging from long-term climate change to predicting the next El Niño.
		However, with the advent of near real-time altimetry data just a few years ago and Web sites that offer help in how to use it, a whole new group of people, such as Captain Greig, are taking advantage of this new information both for work and for pleasure.
		Near real-time altimetry, as global positioning has already done, is working its way from the military and scientific spheres into everyday life.
	www.jpl.nasa.gov /news/features.cfm?feature=609 (849 words)

	ch3
		Surface elevations derived from Magellan altimetry data are thus converted to physical temperature estimates, and used in the above equation to solve for emissivity.
		The altimetry image is extracted from the GTDR file, with a displayed range of planetary radius values from 6047 km to 6058 km.
		The altimetry data convey much topographic information that cannot be gleaned from the SAR image, such as the complex form of the corona trough, the gentle topographic swell outboard of the trough, and the dramatic asymmetric scarp-and-valley features in the central, northern and northwestern portions of the corona.
	history.nasa.gov /JPL-93-24/ch3.htm (3306 words)

	GeoLas Consulting: Laser Altimetry
		Laser altimetry is a fully automatic method of directly measuring the height or elevation of the terrain from an aircraft or a satellite.
		Imaging Laser Altimetry being a direct measurement method generating three-dimensional measurements right away it requires the least manual or interactive effort for data processing of all of the automatic or semi-automatic methods named above.
		Laser altimetry is able to produce DSMs of urban areas with planimetric resolutions in the order of 0.5 - 2 m (2-6 ft).
	www.geolas.com /Pages/laser.html (1780 words)

	Airborne laser altimetry (Site not responding. Last check: 2007-10-15)
		Laser altimetry seems to have opposite advantages and disadvantages compared with the coffee-can method.
		Laser altimetry allows large areas to be surveyed, but it is influenced by short-term variations in snow accumulation rate and densification of the subsurface snow (firn).
		We should then be able to link the snow elevation measured by laser from the aircraft or satellite with the time variation in density (from coffee cans set at different depths) and snowfall.
	www-bprc.mps.ohio-state.edu /GDG/laser.htm (234 words)

	Ocean Surface Topography from Space-Science
		The general circulation and heat budget of the North Pacific Ocean from Satellite altimetry, acoustic tomography, and a general circulation model.
		Chambers, D. Shum, B. Tapley, and R. Stewart, Large-scale, low-frequency variability of the ocean topography observed by satellite altimetry, in Proceedings of the XXI General Assembly, Int.
		Surface manifestation of internal tides in the deep ocean: Observations from altimetry and island gauges.
	topex-www.jpl.nasa.gov /science/investigators-bibliography.html (11792 words)

	Hurricanes and Satellite Altimetry (Site not responding. Last check: 2007-10-15)
		Radar altimetry may be used to indirectly estimate the sea's height anomaly and to make an estimate of the thickness of the warm water layer.
		An increase of 1 cm in sea level represents heating of 1° C for a 100 meter column of sea water.
		Suzanna Barthis a Graduate Research Assistant at CCAR and is actively involved in satellite altimetry research.
	ccar.colorado.edu /~altimetry/applications/hurricanes/index-bv3.html (825 words)

	Remote Sensing Tutorial Page 11-7 (Site not responding. Last check: 2007-10-15)
		Now, altimetry can be done conveniently from space using either radar (microwave) or lidar (light) pulses whose times from satellite to surface and back to satellite provide range information easily converted to distance from the satellite (whose position is accurately known at any moment) to the ground at any spot.
		Timing devices allow extremely precise determination of transit times, so that accuracies of a few centimeters in determining elevations (and their differences or relief) along the traverse are attainable.
		Radar images are capable of displaying the 3-D effect but this is usually not as "realistic" as aerial photography owing to layover, range effects, and other distortions (see page 8-4).
	rst.gsfc.nasa.gov /Sect11/Sect11_7.html (1590 words)

	Altimetry
		Altimetry and Ocean Modeling - research objective is to simulate the ocean circulation and improve it by data assimilation.
		Altimetry Atlas - mean sea surface and gravity anomaly maps of the oceans.
		Ice Altimetry - processing of satellite radar and aircraft laser altimetry over the continental ice sheets and surrounding sea ice to calculate surface elevations.
	ilrs.gsfc.nasa.gov /links/altimetry_links.html (244 words)

	Altimetry, Ocean Currents and the Marine Geoid MIT/EAPS Altimetry (Site not responding. Last check: 2007-10-15)
		A recent review of satellite altimetry with specific focus on TOPEX/POSEIDON results is given by Wunsch and Stammer (1998).
		For a more complete overview, the reader is referred to the two JGR Oceans special TOPEX/POSEIDON issues published in December of the years 1994 and 1995, respectively.
		As the extended mission data become available, and with further analysis of models and in situ data, we anticipate producing a full three dimensional frequency/wavenumber description of oceanic variability extending from about 1 month to order a decade.
	puddle.mit.edu /~detlef/altimetry/altimetry.html (1650 words)

	GeoLas Consulting: Application Examples
		Imaging Laser Altimetry as a direct 3D mapping technique is the method of choice in many of the areas listed below, providing high vertical accuracy and requiring minimal interaction in processing and surface model generation.
		Being a means of accurate three-dimensional imaging of the surface from the air Imaging Laser Altimetry is highly helpful to determine areas prone to natural hazards like floods, and to rapidly asses the damage to infrastructure after natural disasters like earthquakes, storms, landslides on a larger scale.
		Thus it is well suited to for rapid three-dimensional assessment of damage to infrastructure after earthquakes, landslides and storms, enabling a focussed response and concentration of repair forces to the most vital or severely damaged points.
	www.geolas.com /Pages/appls.html (1190 words)

	- Altimetry - Eastern Gulf of Mexico Satellite Imagery
		For current sea surface altimetry imagery, please visit Gulf of Mexico Near-Real-Time Altimetry (University of Colorado).
		Altimetry is shown using 10cm contours above (white) and below (gray) geoid.
		Altimetry values are provided by Colorado Center for Astrodynamics Research (CCAR) at the University of Colorado.
	coastal.er.usgs.gov /cgi-bin/avhrr-sat.pl?site=east_gulf&index=1&type=al (253 words)

	[No title] (Site not responding. Last check: 2007-10-15)
		Altimetry from the Mars Observer Laser Altimeter (MOLA), an instrument on board the Mars Global Surveyor (MGS) spacecraft, has been analyzed for the period of the MGS Science Phasing Orbit-1 (SPO-1) mission phase.
		Altimeter ranges have been used to improve significantly the orbit and attitude knowledge of the spacecraft by the use of crossover constraint equations derived from short passes of the MOLA data.
		The rationale for using this technique with laser altimetry over sloping terrain is laid out and evidence of the resulting benefit is presented.
	earth.agu.org /pubs/abs/gl/1999GL900223/1999GL900223.html (150 words)

	Main Page of Surveying Group
		But exploiting satellite altimetry in coastal areas requires much more sophisticated correction models and data processing techniques than in the open oceans.
		They should be combined with altimetry data for global gravity and geoid computation and estimation of high-degree geopotential model.
		Bathymetry model is an important element in, e.g., the general circulation model of the world oceans and the hydrodynamic tide model, and should be optimally derived with altimetry and other data.
	space.cv.nctu.edu.tw /IAG/main.html (494 words)

	Tides Gauge vs. Altimetry (Site not responding. Last check: 2007-10-15)
		There is no historical altimetry worth talking about, but there is about 100 years or more of tide gauge data.
		While I agree that the future is certainly going to be driven more by satellite altimetry than by the tide gauges, tide gauges will continue to play an important role in the mean sea level problem for the forseeable future.
		Even if there is a break of a a few years in satellite altimetry, the tide gauge data collected during that interval would not provide a reliable figure for any change in global sea level during that period.
	www.pol.ac.uk /psmsl/gb/gb1/tgalt.html (3221 words)

	JCE 1999 (76) 1635 [Dec] Using TOPEX Satellite El Niño Altimetry Data to Introduce Thermal Expansion and Heat ... (Site not responding. Last check: 2007-10-15)
		With appropriate corrections and calibrations the TOPEX altimetry data give an average height over an area 6 to 12 km in diameter accurate to within 3-5 cm, which allows for the detection of large-area, low-profile hills and valleys on the ocean surface.
		The calculations of thermal energy excess in warm-water ocean bumps from radar altimetry data alone, while not unreasonable, must be understood to be a simplification for an extremely complex system.
		The data for the cells and the pictorial representation of the relative TOPEX altimetry data of the Pacific basin were very kindly provided by the TOPEX/Poseidon Project conducted by the Jet Propulsion Laboratory of the California Institute of Technology under contract with NASA.
	jchemed.chem.wisc.edu /journal/issues/1999/dec/abs1635.html (3175 words)

	Improved Free-air Gravity Anomalies by Satellite Altimetry (Site not responding. Last check: 2007-10-15)
		ERS-1 168-day mission altimetry was residualized to a reference geoid surface generated by integrating Anderson and Knudsen¡¯s free-air gravity anomalies for the Barents Sea.
		The altimetry tracks were reduced and filtered to extract the shortest wavelengths (between 4 and 111 km) from both ascending and descending tracks, respectively.
		These data were recombined using existing quadrant-swapping techniques in the wavenumber domain to generate a correlated, high frequency gravity field related to the local geologic sources.
	dasan.sejong.ac.kr /~rigg/jwkim/abstract/improvedFree.htm (127 words)

	GLAS/ICESat L1 and L2 Global Altimetry Data
		Secondary objectives of GLAS are to measure sea ice roughness and thickness, cloud and atmospheric properties, land topography, vegetation canopy heights, ocean surface topography, and surface reflectivity.
		GLAS has a 1064 nm laser channel for surface altimetry and dense cloud heights, and a 532 nm lidar channel for the vertical distribution of clouds and aerosols.
		The GLAS Altimetry Data Dictionary provides further detail about the format of individual parameters, including scaling factors and ranges.
	nsidc.org /data/docs/daac/glas_icesat_l1_l2_global_altimetry.gd.html (5401 words)

	ESA - Observing the Earth - Envisat radar altimetry tracks river levels worldwide
		Hydrologists need no previous knowledge of radar altimetry to make use of the new data, with one product known as River Lake Hydrology providing data corresponding to river crossing points, just as though there were actual river gauges in place.
		Such gauges are the traditional way that river and lake level measurements are obtained, but their number in-situ has declined sharply in the last two decades.
		The other product is called River Lake Altimetry, intended for altimetry specialists, and provides all crossing points for a water body, together with detailed information on all instrumental and geophysical corrections.
	www.esa.int /export/esaSA/SEM7TF0P4HD_earth_0.html (851 words)

	Ocean ESIP Sea Level Data and Altimetry (Site not responding. Last check: 2007-10-15)
		Skylab (1974) demonstrated that satellite altimetry was possible, Geos-3 (1974-77) made measurements good enough for geoid studies, Seasat (1978-78) showed the potential for ocean studies, and Geosat (1985-89) and ERS-1 (1991-1996) produced routine ocean products without the long wavelength components, due to orbit and media errors.
		It now may be feasible to monitor the rise of the global sea level and its potential acceleration, to an accuracy of 1 mm/yr or better.
		The current altimetry missions, ERS-2 (1996-) and especially TOPEX/Poseidon (1992-) added precise, large-scale measurements, allowing retrieval of both fast and interannual sea level variations.
	oceanesip.jpl.nasa.gov /sealevel (487 words)

	TOPEX/POSEIDON Frequently Asked Questions
		The sea surface measured by altimetry is related to the temperature at ALL depths, as well as other parameters, such as the water salinity and ocean currents.
		The measurement geometry and operation principles of the TOPEX Altimeter are very well described in D. Chelton, et als, "Pulse compression and sea level tracking in satellite altimetry", J. Atmospheric and Oceanic Tech., Vol 6, #3, June 1989.
		The altimeter footprint for ocean applications (or other very flat surfaces, relief less than 100 m) is determined by the compressed pulse length (3.125 nsec), the satellite altitude, and the significant wave height.
	www.tsgc.utexas.edu /topex/topexfaq.html (1637 words)

	GSFC ICE ALTIMETRY PAGE (Site not responding. Last check: 2007-10-15)
		There now exists radar altimeter measurements from 1978 through the present of the Greenland and Antarctic Ice sheets, the spatial and temporal coverage is summarized in this table.
		The ice elevation data set (Level 2 - Ice Data Record) consists of the full rate altimetry with location, time, surface height and all pertinent corrections.
		It is mainly used by scientists who are trying to improve the algorithms to calculate the corrections or who require knowledge of what effect the corrections have on the data.
	icesat4.gsfc.nasa.gov /ia_home/hcabufg.html (413 words)

	Altimetry and Hurricane Intensification
		Altimetry and Hurricane Intensification: Upper Ocean Conditions in the Tropical Atlantic, Caribbean Sea and Gulf of Mexico
		The intensification of hurricanes involves a combination of different favorable atmospheric conditions such as atmospheric trough interactions and vertical shear, which lead to good outflow conditions aloft.
		Satellite altimetry data from TOPEX is a useful tool to study oceanic mesoscale dynamic processes from its coverage of the sea height anomaly (SHA) field, and provides information on the vertical ocean structure when complemented by hydrographic data.
	www.aoml.noaa.gov /phod/dataphod/work/goni/cyclone (1024 words)

	Real-Time Altimetry from ERS-2
		One of the great advantages of working with altimetry data from the ERS satellites is the timeliness with which the Fast-Delivery data are received.
		Because of the substantial orbit error present in the RGDRs, further treatment of the sea height data is required to derive accurate maps of sea surface topography.
		The primary benefit of altimetry is that it is an all- weather, and all-season, data source that can be used to continuously monitor the Loop current and its associated eddies.
	ibis.grdl.noaa.gov /SAT/pubs/papers/florence_97 (2894 words)

	NGDC/WDC MGG, Boulder-Measured and Estimated Global Seafloor Topography Info Page
		Analyses of GEOSAT and ERS data from the NOAA Laboratory for Satellite Altimetry
		Global Seafloor Topography from Satellite Altimetry, Walter H.F. Smith and David T. Sandwell,
		Marine Gravity from Satellite Altimetry, David T. Sandwell, Walter H.F. Smith, and Mara M. Yale
	www.ngdc.noaa.gov /mgg/announcements/announce_predict.html (595 words)

	ESEAS: Operational Satellite Altimetry (Site not responding. Last check: 2007-10-15)
		Sea level information may be provided by satellite altimetry (see e.g.
		NASA/JPL or the AVISO altimetry web pages) Especially, altimeter data from the GEOSAT satellite mission (1985-88) and the ongoing ERS and TOPEX/POSEIDON satellite missions have been used in a broad range of sea level analysis and proven its high value in marine research.
		Satellite altimetry may be valuable for the ship traffic and other off-shore activities on an operational basis.
	research.kms.dk /ESEAS (919 words)

	Amazon.co.uk: Books: Satellite Altimetry and the Earth Sciences (A Volume in the INTERNATIONAL GEOPHYSICS Series) (Site not responding. Last check: 2007-10-15)
		Satellite Altimetry and Earth Sciences has integrated the expertise of the leading international researchers to demonstrate the techniques, missions, and accuracy of satellite altimetry, including altimeter measurements, orbit determination, and ocean circulation models.
		Satellite altimetry is helping to advance studies of ocean circulation, tides, sea level, surface waves and allowing new insights into marine geodesy.
		Satellite Altimetry and Earth Sciences is for a very broad spectrum of academics, graduate students, and researchers in geophysics, oceanography, and the space and earth sciences.
	www.amazon.co.uk /exec/obidos/ASIN/0122695453 (745 words)

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