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Zhaohui Li, E Wu, Chengkai Pang, Bingcheng Du, Yuliang Tao, Huan Peng, Heping Zeng, Guang Wu
Photon-counting laser ranging has attracted a lot of research interest for its application in the altimeter. In this letter, we report a large scale multi-beam photon-counting laser imaging system by using 100 laser beams in linear array as the light source. Taking advantage of a 100-channel low-noise high-efficiency single-photon detector, the three-dimensional image of remote targets could be constructed rapidly according to the time-of-flight measurement. This system provides a solution for a high-speed, high-resolution, low energy-consumption pushbroom airborne or spaceborne laser altimeter...
May 1, 2017: Optics Express
Elena López, Sergio García, Rafael Barea, Luis M Bergasa, Eduardo J Molinos, Roberto Arroyo, Eduardo Romera, Samuel Pardo
One of the main challenges of aerial robots navigation in indoor or GPS-denied environments is position estimation using only the available onboard sensors. This paper presents a Simultaneous Localization and Mapping (SLAM) system that remotely calculates the pose and environment map of different low-cost commercial aerial platforms, whose onboard computing capacity is usually limited. The proposed system adapts to the sensory configuration of the aerial robot, by integrating different state-of-the art SLAM methods based on vision, laser and/or inertial measurements using an Extended Kalman Filter (EKF)...
April 8, 2017: Sensors
J Rodrigo, E Gasquet, J-M Castro, M Herranz, L-M Lara, M Muñoz, A Simon, T Behnke, N Thomas
This paper presents the principal considerations when designing DC-DC converters for space instruments, in particular for the power converter module as part of the first European space laser altimeter: "BepiColombo Laser Altimeter" on board the European Space Agency-Japan Aerospace Exploration Agency (JAXA) mission BepiColombo. The main factors which determine the design of the DC-DC modules in space applications are printed circuit board occupation, mass, DC-DC converter efficiency, and environmental-survivability constraints...
March 2017: Review of Scientific Instruments
Ling Zhou, Xianghong Cheng, Yixian Zhu, Chenxi Dai, Jinbo Fu
Terrain-aided navigation is a potentially powerful solution for obtaining submerged position fixes for autonomous underwater vehicles. The application of terrain-aided navigation with high-accuracy inertial navigation systems has demonstrated meter-level navigation accuracy in sea trials. However, available sensors may be limited depending on the type of the mission. Such limitations, especially for low-grade navigation sensors, not only degrade the accuracy of traditional navigation systems, but further impact the ability to successfully employ terrain-aided navigation...
March 25, 2017: Sensors
Melanie N Ott, Joe Thomes, Eleanya Onuma, Robert Switzer, Richard Chuska, Diana Blair, Erich Frese, Marc Matyseck
The Advanced Topographic Laser Altimeter System (ATLAS) Instrument has been in integration and testing over the past 18 months in preparation for the Ice, Cloud and Land Elevation Satellite - 2 (ICESat-2) Mission, scheduled to launch in 2017. ICESat-2 is the follow on to ICESat which launched in 2003 and operated until 2009. ATLAS will measure the elevation of ice sheets, glaciers and sea ice or the "cryosphere" (as well as terrain) to provide data for assessing the earth's global climate changes. Where ICESat's instrument, the Geo-Science Laser Altimeter (GLAS) used a single beam measured with a 70 m spot on the ground and a distance between spots of 170 m, ATLAS will measure a spot size of 10 m with a spacing of 70 cm using six beams to measure terrain height changes as small as 4 mm...
August 28, 2016: Proceedings of SPIE
Rick Lumpkin, Tamay Özgökmen, Luca Centurioni
Surface drifting buoys, or drifters, are used in oceanographic and climate research, oil spill tracking, weather forecasting, search and rescue operations, calibration and validation of velocities from high-frequency radar and from altimeters, iceberg tracking, and support of offshore drilling operations. In this review, we present a brief history of drifters, from the message in a bottle to the latest satellite-tracked, multisensor drifters. We discuss the different types of drifters currently used for research and operations as well as drifter designs in development...
January 3, 2017: Annual Review of Marine Science
J T Fasullo, R S Nerem, B Hamlington
Global mean sea level rise estimated from satellite altimetry provides a strong constraint on climate variability and change and is expected to accelerate as the rates of both ocean warming and cryospheric mass loss increase over time. In stark contrast to this expectation however, current altimeter products show the rate of sea level rise to have decreased from the first to second decades of the altimeter era. Here, a combined analysis of altimeter data and specially designed climate model simulations shows the 1991 eruption of Mt Pinatubo to likely have masked the acceleration that would have otherwise occurred...
2016: Scientific Reports
Farshid Daryabor, See Hai Ooi, Azizan Abu Samah, Abolghasem Akbari
A three-dimensional Regional Ocean Modeling System is used to study the seasonal water circulations and transports of the Southern South China Sea. The simulated seasonal water circulations and estimated transports show consistency with observations, e.g., satellite altimeter data set and re-analysis data of the Simple Ocean Data Assimilation. It is found that the seasonal water circulations are mainly driven by the monsoonal wind stress and influenced by the water outflow/inflow and associated currents of the entire South China Sea...
2016: PloS One
Alba Martín-Español, Andrew Zammit-Mangion, Peter J Clarke, Thomas Flament, Veit Helm, Matt A King, Scott B Luthcke, Elizabeth Petrie, Frederique Rémy, Nana Schön, Bert Wouters, Jonathan L Bamber
We present spatiotemporal mass balance trends for the Antarctic Ice Sheet from a statistical inversion of satellite altimetry, gravimetry, and elastic-corrected GPS data for the period 2003-2013. Our method simultaneously determines annual trends in ice dynamics, surface mass balance anomalies, and a time-invariant solution for glacio-isostatic adjustment while remaining largely independent of forward models. We establish that over the period 2003-2013, Antarctica has been losing mass at a rate of -84 ± 22 Gt yr(-1), with a sustained negative mean trend of dynamic imbalance of -111 ± 13 Gt yr(-1)...
February 2016: Journal of Geophysical Research. Earth Surface
Ma Yue, Wang Mingwei, Li Guoyuan, Lu Xiushan, Yang Fanlin
The current waveform model of a laser altimeter is based on the Gaussian laser beam of the fundamental mode, whose cross section is a circular spot, whereas some of the cross sections of Geoscience Laser Altimeter System lasers are closer to elliptical spots. Based on the expression of the elliptical Gaussian beam and the waveform theory of laser altimeters, the primary parameters of an echo waveform were derived. In order to examine the deduced expressions, a laser altimetry waveform simulator and waveform processing software were programmed and improved under the circumstance of an elliptical Gaussian beam...
March 10, 2016: Applied Optics
C M Risien, P T Strub
We form a new 'blended' data set of sea level anomaly (SLA) fields by combining gridded daily fields derived from altimeter data with coastal tide gauge data. Within approximately 55-70 km of the coast, the altimeter data are discarded and replaced by a linear interpolation between the tide gauge and remaining offshore altimeter data. To create a common reference height for altimeter and tide gauge data, a 20-year mean is subtracted from each time series (from each tide gauge and altimeter grid point) before combining the data sets to form a blended mean sea level anomaly (SLA) data set...
2016: Scientific Data
Angelo Maria Sabatini, Gabriele Ligorio, Andrea Mannini, Vincenzo Genovese, Laura Pinna
This paper investigates a fall detection system based on the integration of an inertial measurement unit with a barometric altimeter (BIMU). The vertical motion of the body part the BIMU was attached to was monitored on-line using a method that delivered drift-free estimates of the vertical velocity and estimates of the height change from the floor. The experimental study included activities of daily living of seven types and falls of five types, simulated by a cohort of 25 young healthy adults. The downward vertical velocity was thresholded at 1...
July 2016: IEEE Transactions on Neural Systems and Rehabilitation Engineering
Vojtěch Michálek, Ivan Procházka, Josef Blažej
During last two decades, several photon counting detectors have been developed in our laboratory. One of the most promising detector coming from our group silicon K14 Single Photon Avalanche Diode (SPAD) is presented with its valuable features and space applications. Based on the control electronics, it can be operated in both gated and non-gated mode. Although it was designed for photon counting detection, it can be employed for multiphoton detection as well. With respect to control electronics employed, the timing jitter can be as low as 20 ps RMS...
2015: Sensors
V K Jineesh, K R Muraleedharan, K Lix John, C Revichandran, P V Hareesh Kumar, K R Naveen Kumar
This manuscript presents the analysis of current meter records at Kollam and Kannur along the 20-m isobaths during November-December 2005. Currents in the coastal waters are strongly influenced by winds (both local and remote forcing), tides, propagation of coastal Kelvin and Rossby waves, etc. We hypothesize that the mesoscale (spatial scales of 10-500 km and temporal scale of 10-100 days) features in ocean are also competent to alter the characteristics of coastal currents to a large extent. Analysis of sea level anomaly from the merged altimeter data reveals the existence of a large anticyclonic eddy in the southeastern Arabian Sea during the winter monsoon...
August 2015: Environmental Monitoring and Assessment
Erwan Mazarico, Michael K Barker, Gregory A Neumann, Maria T Zuber, David E Smith
The Lunar Orbiter Laser Altimeter instrument onboard the Lunar Reconnaissance Orbiter spacecraft collected more than 5 billion measurements in the nominal 50 km orbit over ∼10,000 orbits. The data precision, geodetic accuracy, and spatial distribution enable two-dimensional crossovers to be used to infer relative radial position corrections between tracks to better than ∼1 m. We use nearly 500,000 altimetric crossovers to separate remaining high-frequency spacecraft trajectory errors from the periodic radial surface tidal deformation...
April 16, 2014: Geophysical Research Letters
Makoto Watanabe, Masahiko Murakami, Yoshiaki Ozawa, Marie Uchida, Kimiyasu Yamazaki, Akira Fujimori, Koji Otsuka, Takeshi Aoki
Loop colostomy prolapse is associated with an impaired quality of life. Surgical treatment may sometimes be required for cases that cannot be closed by colon colostomy because of high-risk morbidities or advanced disease. We applied the Altimeter operation for patients with transverse loop colostomy. The Altemeier operation is therefore indicated for rectal prolapse. This technique involves a simple operation, which includes a circumferential incision through the full thickness of the outer and inner cylinder of the prolapsed limb, without incising the abdominal wall, and anastomosis with sutures using absorbable thread...
November 2015: Surgery Today
Fernando S Paolo, Helen A Fricker, Laurie Padman
The floating ice shelves surrounding the Antarctic Ice Sheet restrain the grounded ice-sheet flow. Thinning of an ice shelf reduces this effect, leading to an increase in ice discharge to the ocean. Using 18 years of continuous satellite radar altimeter observations, we have computed decadal-scale changes in ice-shelf thickness around the Antarctic continent. Overall, average ice-shelf volume change accelerated from negligible loss at 25 ± 64 cubic kilometers per year for 1994-2003 to rapid loss of 310 ± 74 cubic kilometers per year for 2003-2012...
April 17, 2015: Science
Mario A Pardo, Tim Gerrodette, Emilio Beier, Diane Gendron, Karin A Forney, Susan J Chivers, Jay Barlow, Daniel M Palacios
We inferred the population densities of blue whales (Balaenoptera musculus) and short-beaked common dolphins (Delphinus delphis) in the Northeast Pacific Ocean as functions of the water-column's physical structure by implementing hierarchical models in a Bayesian framework. This approach allowed us to propagate the uncertainty of the field observations into the inference of species-habitat relationships and to generate spatially explicit population density predictions with reduced effects of sampling heterogeneity...
2015: PloS One
Sheng-Bo Chen, Jing-Ran Wang, Peng-Ju Guo, Ming-Chang Wang
The Moon may be considered as the frontier base for the deep space exploration. The spectral analysis is one of the key techniques to determine the lunar surface rock and mineral compositions. But the lunar topographic relief is more remarkable than that of the Earth. It is necessary to conduct the topographic correction for lunar spectral data before they are used to retrieve the compositions. In the present paper, a lunar Sandmeier model was proposed by considering the radiance effect from the macro and ambient topographic relief...
September 2014: Guang Pu Xue Yu Guang Pu Fen Xi, Guang Pu
David T Sandwell, R Dietmar Müller, Walter H F Smith, Emmanuel Garcia, Richard Francis
Gravity models are powerful tools for mapping tectonic structures, especially in the deep ocean basins where the topography remains unmapped by ships or is buried by thick sediment. We combined new radar altimeter measurements from satellites CryoSat-2 and Jason-1 with existing data to construct a global marine gravity model that is two times more accurate than previous models. We found an extinct spreading ridge in the Gulf of Mexico, a major propagating rift in the South Atlantic Ocean, abyssal hill fabric on slow-spreading ridges, and thousands of previously uncharted seamounts...
October 3, 2014: Science
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