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1.
Airborne laser scanning (ALS) is an active remote sensing technique providing range data as 3D point clouds. This paper aims at presenting a survey of the literature related to such techniques, with emphasis on the new sensors called full-waveform lidar systems. Indeed, an emitted laser pulse interacts with complex natural and man-made objects leading to a temporal distortion of the returned energy profile. The new technology of full-waveform laser scanning systems permits one to digitize the complete waveform of each backscattered pulse. Full-waveform lidar data give more control to an end user in the interpretation process of the physical measurement and provide additional information about the structure and the physical backscattering characteristics of the illuminated surfaces. In this paper, the theoretical principles of full-waveform airborne laser scanning are first described. Afterwards, a review of the main sensors as well as signal processing techniques are presented. We then discuss the interpretation of full-waveform measures with special interest on vegetated and urban areas. 相似文献
2.
J. L. Mallet 《Mathematical Geology》1988,20(8):977-990
Lett= (x, y, z) be an ore grade function sampled at the nodes of a three dimensional regular grid. Ift
0 is a given cut-off, the ore deposit may be considered to be constituted by all the points (x, y, z) such that (x, y, z)>t
0. In fact, the ore deposit may be constituted by one or several disconnected bodies and two algorithms to display these bodies may be considered. The first consists in drawing intersections of the bodies with a series of equidistant parallel planes. The second consists in covering their surface with painted triangles. In both cases, how to remove hidden parts of the drawing is shown. An interactive approach of the problem also is considered.This paper presented at Emerging Concepts, MGUS-87 conference, Redwood City, California, 13–15 April 1987. 相似文献
3.
This paper addresses the problem of characterizing the shape of a geological surface on the basis of its principal curvatures.
The surface is assumed to be modeled as a set of adjacent triangles defined by the location of their vertices and a method
is proposed for estimating numerically the principal curvatures at the vertices of the triangles using a local C2 interpolant. Also shown is how principal curvatures can be useful for studying the deformation of a geological surface (with
application to 3D balanced unfolding), and analyzing the folding or faulting of the interface between two adjacent layers. 相似文献
4.
Dan Eude Kpannieu Martine Mallet Lacina Coulibaly Mustapha Abdelmoula Christian Ruby 《Comptes Rendus Geoscience》2019,351(1):37-47
Aqueous phosphate removal by three geomaterials from Ivory Coast was evaluated to determine their potential application as low-cost phosphate adsorbents in wastewater treatment. Batch experiments showed that phosphate uptake strongly depended on pH. Laterite and sandstone dissolution was less pronounced compared to shale. A correlation between concentrations of aqueous cation species released from shale and phosphate uptake was observed. The kinetics were well described using the pseudo-second-order model. Isotherms displayed a saturation level on shale, while phosphate uptake continuously increased for laterite and sandstone. The removal efficiency decreased in the following ranking order: laterite > sandstone > shale. Laterite was also the most efficient adsorbent in column experiments. The high phosphate removal efficiency of laterite (8.3 mg PO4 g?1) was attributed to the presence of superparamagnetic low grain sizes of goethite. Laterite is a particularly promising material for further investigation in wastewater treatment technology such as constructed wetlands. 相似文献
5.
Compilation of the offshore and onshore altitudinal limits of the loess deposits of western France and southern England shows that they were deposited by low-level wind fields. These relate to (i) the deflation of silt-rich sediment extracted from the outwash plains of the not far distant British–Irish Ice Sheet and from the palaeo-rivers of the Channel, and (ii) the existence of north and north-western palaeo-winds deduced from particle size analysis and heavy mineral distribution, and suggest (iii) that loess particles were transported by strong katabatic winds blowing from the northern ice-covered regions towards Brittany and Normandy. Comparison between the main orientation of Neanderthal shelters and the direction of the katabatic winds shows that they were perpendicular to each other. The dominant orientation of the shelters was apparently ruled by these winds. A small-scale study concentrating on the penultimate glaciation shows that in contrast to Brittany and Normandy where loess deposits accumulated on north-facing cliffs, in England the same particles were deposited on the leeside of the hills. The existence of deflation zones, violently swept by Marine Isotope Stage 6 katabatic winds south of the British–Irish ice sheet, was probably at the origin of the restricted number of Neanderthals at that time in England. © 2021 John Wiley & Sons, Ltd. 相似文献
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At‐sea sampling is a common approach used by fisheries scientists to assess changes in fished populations. Traditional sampling programmes focus on short intensive sampling periods by fisheries personnel, although there has been a move to increase temporal sampling frequency within a fishing season by using harvesters. To determine the suitability of these two options, we compared the precision of estimates obtained for the American lobster (Homarus americanus) fishery in the southern Gulf of St. Lawrence, Canada. The sampling variance estimation for the mean catch‐per‐unit‐effort (CPUE) was based on a three‐stage sampling design with days as the primary unit, and buoy and trap as secondary and third stage units, respectively. Using the estimated variance components to predict and compare the variance of the mean CPUE for different at‐sea sampling designs, we show that it would be more efficient to sample a few traps (at least 3) every day for the entire fishing season than the traditional at‐sea sampling of the entire fishing gear twice or three times in a season by scientific personnel. Designing a harvester‐based at‐sea sampling programme could be an efficient approach for reducing costs while gathering essential fishery data, improving dialogue between the industry and scientists, and increasing harvesters’ participation in managing the resource. 相似文献
8.
In this, the seventh in an occasional series of earth phenomena the author recounts tales of sudden flames issuing from the ground, paroxysmal eruptions and serpent spirits presiding over volcanoes. 相似文献
9.
V. A. Kudryavtsev N. J. C. Spooner P. K. Lightfoot J. W. Roberts M. J. Lehner T. Gamble M. J. Carson T. B. Lawson R. Lüscher J. E. McMillan B. Morgan S. M. Paling M. Robinson D. R. Tovey N. J. T. Smith P. F. Smith G. J. Alner S. P. Hart J. D. Lewin R. M. Preece T. J. Sumner W. G. Jones J. J. Quenby B. Ahmed A. Bewick D. Davidge J. V. Dawson A. S. Howard I. Ivaniouchenkov M. K. Joshi V. Lebedenko I. Liubarsky J. C. Barton G. Gerbier J. Mallet L. Mosca C. Tao 《Astroparticle Physics》2002,17(4):79-408
The status of dark matter searches with inorganic scintillator detectors at Boulby mine is reviewed and the results of tests with a CsI(Tl) crystal are presented. The objectives of the latter experiment were to study anomalous fast events previously observed and to identify ways to remove this background. Clear indications were found that these events were due to surface contamination of crystals by alphas, probably from radon decay. A new array of unencapsulated NaI(Tl) crystals immersed either in liquid paraffin or pure nitrogen atmosphere is under construction at Boulby. Such an approach allows complete control of the surface of the crystals and the ability to remove any surface contamination. First data from the unencapsulated NaI(Tl) do not show the presence of anomalous fast events. 相似文献
10.
Discrete modeling for natural objects 总被引：14，自引：0，他引：14
J. L. Mallet 《Mathematical Geology》1997,29(2):199-219
This paper presents a discrete technique specially designed for modeling the geometry and the properties of natural objects
as those encountered in biology and geology. Contrary to classical Computer- Aided Design methods based on continuous (polynomial)
functions, the proposed approach is based on a discretization of the objects close to the finite- element techniques used
for solving differential equations. Each object is modeled as a set of interconnected nodes holding the geometry and the physical
properties of the objects and the Discrete Smooth Interpolation method is used for fitting the geometry and the properties
to complex data. Data are turned into linear constraints and some constraints related to typical information encountered in
geology are presented. 相似文献