Growing stock estimation through stratified sampling on satellite remote sensing data     

Inderjit Singh  P. S. Roy 《Journal of the Indian Society of Remote Sensing》1990,18(1-2):29-42

Aerial photographs are being extensively used for forest surveys i.e. forest cover type mapping, assessment of growing stock, estimation of area, vegetation studies, etc. Satellite remote sensing technology offers new possibilities and scope for achieving some of the above applications with higher accuracy and reliability. The assessment of growing stock through subjective stratification has also become possible with increase in spatial and spectral resolution. In the present study, the LANDSAT TM FCC (1966) has been visually interpreted on the basis of tonal characteristics. Stratified random sampling method has then used for determination of number of sample units for collection of ground Inventory data. Using regression equations, the volume per hectare of individual forest cover types were calculated. Satellite remote sensing data has been used for initial stratification, distribution of sample plots and calculation of area under various forest cover types. Estimate has been made for available commecial and non-commercial growing stocks in the study area.  相似文献   

Nepal highway alignment survey and aspects of integrated approach for route alignment study     

V. K. Jha  A. K. Roy  D. K. Jugran 《Journal of the Indian Society of Remote Sensing》1988,16(1):79-84

Satellite and aerial remote sensing techniques can provide useful, indicative information on most of the factors that are pertinent to a good route location. This information because it is obtained quickly, economically, and with fair to excellent dependability for large areas, can then be translated into better planning, design and constructions as well as lower maintenance cost. The Nepal highway project involved, besides study of geology, the mapping and delineation of land facets through which the route would pass, and included the study of (i) rock, (2) soil, (3) weathering, (4) slopes, (5) landslides, (6) hydrology and (7) construction material availability in an integrated manner. Remote sensing techniques helped in efficient selection of potential route than could have been possible by conventional ground techniques alone.  相似文献   

Erosion of the eastern United States observed with 10Be     

Louis Brown  Milan J. Pavich  R. E. Hickman  Jeffrey Klein  Roy Middleton 《地球表面变化过程与地形》1988,13(5):441-457

The problem of identifying areas of accelerated erosion in a dynamic landscape is complicated. The limited history of sediment yield measurements makes this task difficult even if geomorphic evidence is available. Beryllium-10, a cosmogenic isotope produced by cosmic rays interacting with the earth's atmosphere and surface, has chemical and physical properties that make it useful as a tracer for erosion and sediment transport processes. The rarity of the stable isotope, ⁹Be, allows ¹⁰Be to be detected with accelerator mass spectrometry in natural materials at extremely low levels. Backgrounds for rocks and sediments below 10⁵ atom per g are now attainable, a value to be compared with an average deposition rate of 1.3 × 10⁶ atom cm^?2 yr^?1. The affinity of Be for the components of soil and sediment is sufficiently high that it is effectively immobilized on contact, thereby allowing ¹⁰Be to function as a tracer of sediment transport. To a good approximation all the ¹⁰Be transport out of a drainage basin is on the sediment leaving it. The number of ¹⁰Be atoms passing the gauging station can be determined by measuring the concentration of the isotope in the sediment, if the annual sediment load is known. The ratio of the ¹⁰Be carried from the basin by the sediment to that incident upon it, called the erosion index, has been determined for 48 drainage basins within the same physiographic province, which allows them to be reasonably compared, all of which have sediment yield data. Basins located in the Atlantic coastal plain have an average index of 0.3 with the maximum observed being 0.9. Basins located between the fall line and the mountains, a region called the Piedmont, have an average value of 2.2 with individual values ranging from 0.6 to 6.7; this marked difference is thought to result from two centuries of farming on land of moderate gradient. Basins in the highland regions reflect local conditions with low indices for those in grass and timber and high indices associated with destructive land use. The data allow an estimate of the erosion index for the pre-colonial Piedmont, which then allows the pre-colonial sediment yield to be calculated. A number of basins have also been examined world wide with similar conclusions derived. An important deviation from the rule is noted for rivers that erode large regions of loess, such as the Mississippi, Hwang Ho, and Yangtze. Large aeolian deposits were laid down during the ice age in these basins, deposits that brought inherited ¹⁰Be with them and that are easily eroded.  相似文献   

MEG Investigation of Low Pressure Silica — Shell model for polarization     

Mark D. Jackson  Roy G. Gordon 《Physics and Chemistry of Minerals》1988,16(3):212-220

We present a two-shell polarization model for the α-quartz and α-cristobalite structures. By allowing for polarization, we correct problems encountered in purely ionic bonding treatments of tetrahedrally coordinated silica phases. The shell model predicts zero pressure structures in very good agreement with experiment using no empirical parameters. The behavior of the shell model α-quartz lattice upon compression shows dramatic improvement over the distorted, rigid lattice given by the ionic model.  相似文献   

Columbia Bay, Alaska: an ‘upside down’ estuary     

Roy A. Walters  E. G. Josberger  C. L. Driedger 《Estuarine, Coastal and Shelf Science》1988,26(6)

Circulation and water properties within Columbia Bay, Alaska, are dominated by the effects of Columbia Glacier at the head of the Bay. The basin between the glacier terminus and the terminal moraine (sill depth of about 22 m) responds as an ‘upside down’ estuary with the subglacial discharge of freshwater entering at the bottom of the basin. The intense vertical mixing caused by the bouyant plume of freshwater creates a homogeneous water mass that exchanges with the far-field water through either a two- or a three-layer flow. In general, the glacier acts as a large heat sink and creates a water mass which is cooler than that in fjords without tidewater glaciers. The predicted retreat of Columbia Glacier would create a 40 km long fjord that has characteristics in common with other fjords in Prince William Sound.  相似文献   

Display of acoustic reflection profiles using a dot matrix plotter     

S.D. Milligan  L.R. LeBlanc  F.H. Middleton 《Ocean Engineering》1976,3(4)

Acoustic reflection profiling data display is traditionally done with the aid of a facsimile type of recorder. It is not uncommon to record the unprocessed acoustic data on a tape recorder for subsequent playback through a laboratory computer. This still involves the use of some sort of facsimile recorder for the ultimate display of profiles. This paper presents the results of a study to adapt a high-speed digital dot matrix plotter for the ultimate display in place of the conventional facsimile recorder. Because a minicomputer drives the display directly, a host of signal conditioning procedures are permitted, with the final display being generated in real time. Algorithms are developed to control the marking density, allow adaptive threshold control, bottom tracking, automatic gain control, and de-emphasis of water column boundary reverberation. These techniques are just a few of the many that can be employed since the computer can readily be carried on a large ship in deep water, or a small vessel in a harbour. Shallow water is the difficult case for high energy acoustic sources because the water column boundaries behave much like an excited acoustic cavity. For this reason, a section of seismic profile is shown which was obtained with a 7·5 kHz pinger in only 8 m of water in Narragansett Bay. This research was partiallysupported by the Division of Computer Research of the National Science Foundation.  相似文献   

Multivariate analysis as a tool to infer hydrologic response types and controlling variables in a humid temperate catchment     

Genevive A. Ali  Andr G. Roy  Marie‐Claude Turmel  Franois Courchesne 《水文研究》2010,24(20):2912-2923

We assess the ability of multivariate statistical analyses applied to event hydrographs parameters, to characterize a catchment hydrological behaviour. Motivation for such an approach lies in the fact that streamflow records have yet to be exploited to their full potential towards hydrological interpretation and can be used to infer a catchment state of connectivity from a qualitative standpoint. We have therefore processed 96 event hydrographs from a small headwater temperate humid forested catchment using principal component analysis, variation partitioning and classification tree analysis. These techniques prove to be promising in discriminating contrasted types of hydrologic responses (e.g. low‐ vs high‐magnitude events, slow vs quick timing events), identifying the main hydro‐meteorological variables that control these responses and determining thresholds values of the hydro‐meteorological variables leading to a switch between catchment response types. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Geochemical record of Late Quaternary paleoclimate from lacustrine sediments of paleo-lake San Felipe,western Sonora Desert,Mexico     

P.D. Roy  M. Caballero  R. Lozano  B. Ortega  S. Lozano  T. Pi  I. Israde  O. Morton 《Journal of South American Earth Sciences》2010,29(3):586-596

Stratigraphy, mineralogy, major and trace elements, organic carbon, carbonate, sulfate and AMS ¹⁴C dates are used to infer Late Quaternary depositional environments and paleo-hydrological conditions in the paleo-lake San Felipe located in the western part of Sonora Desert. Sediment stratigraphy divides the depth profile into aeolian and pluvio-lacustrine regimes. Aeolian regime is constrained to >44.5 ¹⁴C kyr BP. The pluvio-lacustrine regime consists of two stratigraphic units with characteristic geochemical proxies indicating changing chemical weathering, clastic input, salinity and provenance and provides a measure of varying climatic conditions between ca. 37 and 3 ¹⁴C kyr BP. Lower catchment erosion and inflow into the basin, higher lake productivity, precipitation of Na-sulfate mineral and higher clastic input from the proximal aeolian deposits during ca. 37–14 ¹⁴C kyr BP are comparable to the regional registers of dominant winter rainfall related to westerly storm tracks and colder conditions. In the last 12 ¹⁴C kyr BP, higher sedimentation and inflow and lower productivity are comparable to dominant summer rainfall. Higher humidity and lake productivity during ca. 37–29 ¹⁴C kyr BP is possibly due to the position of westerly storm tracks at 31°N and the gradually reducing humidity till ca. 14 ¹⁴C kyr BP is related to northerly migration of westerly storm tracks. Regional arid conditions during ca. 11 ¹⁴C kyr BP and ca. 6 ¹⁴C kyr BP are characterized by influx of coarser quartz and feldspars into the basin.  相似文献   

Retracted and replaced: A modelling study of hyporheic exchange pattern and the sequence,size, and spacing of stream bedforms in mountain stream networks,Oregon, USA     

Michael N. Gooseff  Justin K. Anderson  Steven M. Wondzell  Justin LaNier  Roy Haggerty 《水文研究》2005,19(15):2915-2929

This article has been retracted and replaced. See Retraction and Replacement Notice DOI: 10.1002/hyp.6350 Studies of hyporheic exchange flows have identified physical features of channels that control exchange flow at the channel unit scale, namely slope breaks in the longitudinal profile of streams that generate subsurface head distributions. We recently completed a field study that suggested channel unit spacing in stream longitudinal profiles can be used to predict the spacing between zones of upwelling (flux of hyporheic water into the stream) and downwelling (flux of stream water into the hyporheic zone) in the beds of mountain streams. Here, we use two‐dimensional groundwater flow and particle tracking models to simulate vertical and longitudinal hyporheic exchange along the longitudinal axis of stream flow in second‐, third‐, and fourth‐order mountain stream reaches. Modelling allowed us to (1) represent visually the effect that the shape of the longitudinal profile has on the flow net beneath streambeds; (2) isolate channel unit sequence and spacing as individual factors controlling the depth that stream water penetrates the hyporheic zone and the length of upwelling and downwelling zones; (3) evaluate the degree to which the effects of regular patterns in bedform size and sequence are masked by irregularities in real streams. We simulated hyporheic exchange in two sets of idealized stream reaches and one set of observed stream reaches. Idealized profiles were constructed using regression equations relating channel form to basin area. The size and length of channel units (step size, pool length, etc.) increased with increasing stream order. Simulations of hyporheic exchange flows in these reaches suggested that upwelling lengths increased (from 2·7 m to 7·6 m), and downwelling lengths increased (from 2·9 m to 6·0 m) with increase in stream order from second to fourth order. Step spacing in the idealized reaches increased from 5·3 m to 13·7 m as stream size increased from second to fourth order. Simulated upwelling lengths increased from 4·3 m in second‐order streams to 9·7 m in fourth‐order streams with a POOL–RIFFLE–STEP channel unit sequence, and increased from 2·5 m to 6·1 m from second‐ to fourth‐order streams with a POOL–STEP–RIFFLE channel unit sequence. Downwelling lengths also increased with stream order in these idealized channels. Our results suggest that channel unit spacing, size, and sequence are all important in determining hyporheic exchange patterns of upwelling and downwelling. Though irregularities in the size and spacing of bedforms caused flow nets to be much more complex in surveyed stream reaches than in idealized stream reaches, similar trends emerged relating the average geomorphic wavelength to the average hyporheic wavelength in both surveyed and idealized reaches. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

Critical properties of spherically symmetric accretion in a fractal medium     

Nirupam Roy  Arnab K. Ray 《Monthly notices of the Royal Astronomical Society》2007,380(2):733-740

Spherically symmetric transonic accretion of a fractal medium has been studied in both the stationary and the dynamic regimes. The stationary transonic solution is greatly sensitive to infinitesimal deviations in the outer boundary condition, but the flow becomes transonic and stable when its evolution is followed through time. The evolution towards transonicity is more pronounced for a fractal medium than it is for a continuum, and in the former case the static sonic condition is met on relatively larger length scales. The dynamic approach also shows that there is a remarkable closeness between an equation  of motion for a perturbation in the flow, and the metric of an analogue acoustic black hole. The stationary inflow solutions of a fractal medium are as much stable under the influence of linearized perturbations as they are for the fluid continuum.  相似文献