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Sheng Nie, Cheng Wang, Xiaohuan Xi, Shezhou Luo, Guoyuan Li, Jinyan Tian, Hongtao Wang
The upcoming space-borne LiDAR satellite Ice, Cloud and land Elevation Satellite-2 (ICESat-2) is scheduled to launch in 2018. Different from the waveform LiDAR system onboard the ICESat, ICESat-2 will use a micro-pulse photon-counting LiDAR system. Thus new data processing algorithms are required to retrieve vegetation canopy height from photon-counting LiDAR data. The objective of this paper is to develop and validate an automated approach for better estimating vegetation canopy height. The new proposed method consists of three key steps: 1) filtering out the noise photons by an effective noise removal algorithm based on localized statistical analysis; 2) separating ground returns from canopy returns using an iterative photon classification algorithm, and then determining ground surface; 3) generating canopy-top surface and calculating vegetation canopy height based on canopy-top and ground surfaces...
May 14, 2018: Optics Express
Nathaniel E Putzig, Isaac B Smith, Matthew R Perry, Frederick J Foss, Bruce A Campbell, Roger J Phillips, Roberto Seu
Over the last decade, observations acquired by the Shallow Radar (SHARAD) sounder on individual passes of the Mars Reconnaissance Orbiter have revealed the internal structure of the Martian polar caps and provided new insights into the formation of the icy layers within and their relationship to climate. However, a complete picture of the cap interiors has been hampered by interfering reflections from off-nadir surface features and signal losses associated with sloping structures and scattering. Foss et al...
July 1, 2018: Icarus
Song Li, Wenhao Zhang, Yue Ma, Xiao Hua Wang, Fanlin Yang, Dianpeng Su
Current land-cover classification methods using ICESat/GLAS's (Ice, Cloud, and land Elevation Satellite/Geoscience Laser Altimeter System) datasets are based on empirical thresholds or machine learning by training multiple GLAS parameters, e.g., the reflectivity and elevation of the target and width, amplitude, kurtosis, and skewness of the return waveform. A theoretical classifier is derived based on a waveform model of an actual laser altimeter illuminating the sea surface. With given system parameters and the sea surface wind corresponding to the location of a laser footprint (the wind can be calculated by using the National Centers for Environmental Prediction dataset), a precise theoretical waveform can be generated as a reference...
April 1, 2018: Applied Optics
R S Nerem, B D Beckley, J T Fasullo, B D Hamlington, D Masters, G T Mitchum
Using a 25-y time series of precision satellite altimeter data from TOPEX/Poseidon, Jason-1, Jason-2, and Jason-3, we estimate the climate-change-driven acceleration of global mean sea level over the last 25 y to be 0.084 ± 0.025 mm/y2 Coupled with the average climate-change-driven rate of sea level rise over these same 25 y of 2.9 mm/y, simple extrapolation of the quadratic implies global mean sea level could rise 65 ± 12 cm by 2100 compared with 2005, roughly in agreement with the Intergovernmental Panel on Climate Change (IPCC) 5th Assessment Report (AR5) model projections...
February 27, 2018: Proceedings of the National Academy of Sciences of the United States of America
F S Paolo, L Padman, H A Fricker, S Adusumilli, S Howard, M R Siegfried
Satellite observations over the past two decades have revealed increasing loss of grounded ice in West Antarctica, associated with floating ice shelves that have been thinning. Thinning reduces an ice-shelf's ability to restrain grounded-ice discharge, yet our understanding of the climate processes that drive mass changes is limited. Here, we use ice-shelf height data from four satellite altimeter missions (1994-2017) to show a direct link between ice-shelf-height variability in the Antarctic Pacific sector and changes in regional atmospheric circulation driven by the El Niño-Southern Oscillation...
2018: Nature Geoscience
Yue Ma, Song Li, Wenhao Zhang, Zhiyu Zhang, Hui Zhou, Ma Xin
The echo width is one of the most essential parameters of waveforms, which can be used to evaluate the ranging performance of a laser altimeter or retrieve wind speeds when laser pulses illuminate on the sea surface. The classical expression of waveform widths is not suitable for a current satellite laser altimeter because only the waves on the sea with smaller wavelengths can be covered by a satellite laser altimeter due to its small footprint. A new expression is derived by dividing the broadening effect of echo widths into the wind wave with small wavelengths and the swell cause with large wavelengths...
August 1, 2017: Applied Optics
Junfeng Xie, Xinming Tang, Fan Mo, Guoyuan Li, Guangbin Zhu, Zhenming Wang, Xingke Fu, Xiaoming Gao, Xianhui Dou
Successfully launched on 30 May 2016, ZY3-02 is the first Chinese surveying and mapping satellite equipped with a lightweight laser altimeter. Calibration is necessary before the laser altimeter becomes operational. Laser footprint location prediction is the first step in calibration that is based on ground infrared detectors, and it is difficult because the sample frequency of the ZY3-02 laser altimeter is 2 Hz, and the distance between two adjacent laser footprints is about 3.5 km. In this paper, we build an on-orbit rigorous geometric prediction model referenced to the rigorous geometric model of optical remote sensing satellites...
September 21, 2017: Sensors
Matteo Albéri, Marica Baldoncini, Carlo Bottardi, Enrico Chiarelli, Giovanni Fiorentini, Kassandra Giulia Cristina Raptis, Eugenio Realini, Mirko Reguzzoni, Lorenzo Rossi, Daniele Sampietro, Virginia Strati, Fabio Mantovani
Flight height is a fundamental parameter for correcting the gamma signal produced by terrestrial radionuclides measured during airborne surveys. The frontiers of radiometric measurements with UAV require light and accurate altimeters flying at some 10 m from the ground. We equipped an aircraft with seven altimetric sensors (three low-cost GNSS receivers, one inertial measurement unit, one radar altimeter and two barometers) and analyzed ~3 h of data collected over the sea in the (35-2194) m altitude range. At low altitudes (H < 70 m) radar and barometric altimeters provide the best performances, while GNSS data are used only for barometer calibration as they are affected by a large noise due to the multipath from the sea...
August 16, 2017: Sensors
Tianjin Huang, Li Jia, Massimo Menenti, Jing Lu, Jie Zhou, Guangcheng Hu
We present in this paper a polynomial fitting method applicable to segments of footprints measured by the Geoscience Laser Altimeter System (GLAS) to estimate glacier thickness change. Our modification makes the method applicable to complex topography, such as a large mountain glacier. After a full analysis of the planar fitting method to characterize errors of estimates due to complex topography, we developed an improved fitting method by adjusting a binary polynomial surface to local topography. The improved method and the planar fitting method were tested on the accumulation areas of the Naimona'nyi glacier and Yanong glacier on along-track facets with lengths of 1000 m, 1500 m, 2000 m, and 2500 m, respectively...
August 5, 2017: Sensors
F Giannessi, L Ryskalin, R Ruffoli
The paratympanic organ (PTO) is a sensory organ located in the medial wall of the tympanic cavity of birds. The organ looks like a small tapering vesicle, and is equipped with a sensory epithelium formed by supporting cells (SCs) and Type II hair cells (Type II-HCs). The function of the PTO has not yet been precisely defined. The prevailing current hypothesis is that the PTO assesses the air pressure exerted on the external surface of the tympanic membrane. The PTO could may thus function as a barometer and, in flying birds, also as an altimeter...
July 1, 2017: Archives Italiennes de Biologie
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...
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...
August 10, 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
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