Scale Spatial Resolution Research Articles

Spatially explicit models of fish production: The integration of acoustics and bioenergetics.

Acoustic sensors provide detailed information on biological structure in the sea at relatively fine spatial and temporal scales of resolution. Using a newly developed acoustic visualization and information retrieval (AVAIR) system, this acoustical information is more fully exploited by coupling acoustic data on prey sizes and density and measures of the physical habitat with species-specific bioenergetic models of fish growth rate. The result is a two-dimensional spatial model of fish growth rate potential and system production that has statistical properties and dynamics that differ from those of the underlying physical and biological structure of the system. Given the nonlinearity of most biological processes (growth, production, foraging, behavior), it is argued that such spatially (and temporally) explicit modeling is necessary to link biological processes to physical and biological structure and to predict how changes in patterning and scaling of the environment might affect such higher-order features of the environment.

Numerical modeling of tide and current in Central Puget Sound: Comparison of a three‐dimensional and a depth‐averaged model

A depth‐averaged and a three‐dimensional hydrodynamics model were applied in a study to evaluate quantitative methods for characterizing tide and current in one of the major basins of Puget Sound. The objective of the investigation was to assess the models' performance and operational requirements for future management applications. The study found that at the chosen horizontal spatial resolution scale of 762 m, both models were capable of reproducing major observed tide and tidal current characteristics in the study area and the differences between the results of the two models are small. Typical runs of the models with the current resolution require about 6–20 System Resources Units on a CRAY X/MP‐48 supercomputer. For future simulation of general tidal circulation and transport features in the Sound, the use of depth‐averaged models with spatial resolution of 800 m or less is recommended. For certain management problems around the Sound (for example, outfall siting, dredge material disposal) in which more detailed knowledge of the tidal current might be useful, the use of three‐dimensional models with finer spatial resolution (300 m or less horizontally and 15–50 m vertically) is suggested. The study also demonstrated that with increasing availability of computing power, wider use of multidimensional hydrodynamics models for estuarine environmental decision making as well as basic scientific research is very promising.

Progress and Prospects of Materials Characterization at Subnanometer Spatial Resolution using Finely Focussed Electron Beams

ABSTRACTThe prospects of microanalysis using 0.5 nm diameter electron beams are reviewed. This paper will discuss the various characterization possibilities with emphasis on incoherent imaging, energy loss spectroscopy and convergent probe diffraction. Some examples indicating characterization at a 0.5 nm lateral spatial resolution scale will be presented and we will conclude with a discussion of the limits of nanometer characterization.

Habitat Associations and Community Structure of Birds in Shrubsteppe Environments

We studied the relations between bird distribution and abundance and habitat characteristics at a regional scale of investigation, using surveys conducted over three consecutive years on 14 plots at nine locations in the shrubsteppe of the northwestern Great Basin of North America. Bivariate and multivariate analyses revealed no large suites of bird species that were correlated in their distribution and abundance, and few associations existed between pairs of species, suggesting that bird populations in this system vary largely independently of one another. Both bivariate and multivariate correlational analyses between birds and habitat physiognomy indicated that the bird species that were widely distributed in this shrubsteppe system had few significant associations with habitat features, while species with more localized distributions did exhibit habitat affinities, most notably with a suite of characters associated with the occurrence of rocky outcrops. Bird species whose primary distributions and habitat affinities lie in grassland regions to the east demonstrated the greatest degree of correlation with features of habitat physiognomy in this shrubsteppe region, increasing in abundance as vegetation coverage and stature increased and horizontal heterogeneity of habitats decreased. Some bird species, however, exhibited no correlations with the habitat features we measured, and multivariate analyses comparing variation in the bird abundances with variation in features of habitat physiognomy accounted for <17% of the overall variation in the bird abundance matrix. Consideration of coverages of different species of shrubs, however, generally produced more significant correlations with variations in bird abundances, especially for the widespread shrubsteppe species. Attributes of avian community structure varied among the locations surveyed. Variations in the abundance of Brewer's Sparrows, the most abundant species at most sites, accounted for 86% of the variation in total avian density. Species diversity was negatively correlated with total density (presumably because of the overwhelming influence of one species on density) but positively correlated with species richness. Richness variations, in turn, were a consequence of variations in the abundances of several locally distributed shrubsteppe species or grassland species. Richness decreased with increasing horizontal habitat heterogeneity and general vegetation sparseness, but increased with increasing structural diversity of the habitat. Variations in avian community biomass were largely a function of abundances of the widespread or peripheral species; none of the local shrubsteppe forms that contributed so much to species richness was correlated with total biomass variations. We compare the findings of these regional—scale analyses with those of a continental—scale study that included a habitat spectrum ranging from shrubsteppe through tallgrass prairies. Bird species exhibited different patterns of habitat correlations on the two spatial scales. In particular, the characteristic shrubsteppe species showed strong correlations with features of habitat physiognomy in the continental analysis, but in the regional study such associations were generally lacking and these birds instead were correlated with the coverages of various shrub species. This suggests that at a large scale, between—habitat level of analysis these birds may respond to some elements of general habitat configuration, but their within—habitat responses may be more strongly associated with details of habitat floristics. These results complicate studies of avian community/habitat relationships: complete understanding of ecological patterns apparently requires knowledge of vegetational floristics as well as physiognomy; the response of birds to habitat characteristics, and the habitat features that are important, may differ at different scales of spatial resolution. At both spatial scales, however, a substantial portion of the variation in avian abundance remains unexplained after consideration of habitat features. Relatively few significant correlations thus emerge, increasing the probability that those that are revealed may well be spurious, and reinforcing the view that biotic interactions such as competition probably play a minor role in structuring these communities.

Deconvolution of Wide Field-of-View Radiometer Measurements of Earth-Emitted Radiation. Part I: Theory

The problem of relating satellite measurements from wide field-of-view (WFOV) radiometers to the radiant exitance emitted from the top of the atmosphere is treated. The problem is formulated as an integral equation to be solved for the radiant exitance distribution in terms of the measurements. An analytical solution to this integral equation in terms of spherical harmonies is presented for the case in which the directional dependence of the outgoing radiation is a function of zenith angle only. It is shown that the resolution which can be obtained under real conditions is limited. The sensitivity of the derived radiant exitance distribution to the directional dependence of the out-going radiation is studied, and results are presented for WFOV flat-plate and spherical radiometers and for restricted field-of-view flat-plate radiometers. It is demonstrated that this sensitivity is a function of the scale of spatial resolution; thus higher resolutions in the radiant exitance distribution are more sensitive to variations in the directional dependence. The technique is applied to measurements of earth-emitted radiation from the Nimbus 6 ERB (Earth Radiation Budget) experiment WFOV radiometer to produce a resolution enhanced map of emitted radiation for the month of August 1975. For this case, the limit of resolution appeared to be spherical harmonies of degree 15. Comparison with results from the ERB scanning radiometer shows very good agreement.

Transitivity, spatially separable utility functions, and United States migration streams, 1935-1970.

The predictions of spatial-interaction models applied to migration systems may be viewed as the outcome of expected-utility maximization in which the average beliefs and preferences at a given origin are spatially separable. This theory indicates that a test of the spatial separability of the utilities may be performed by examining the degree of transitivity in probabilities and gross flows that is predicted by the spatial-interaction models. United States migration data for four periods between 1935 and 1970 were examined for transitivity at three spatial scales of resolution. These flows all exhibited significantly high degrees of transitivity, although for no period or scale of resolution were migration flows completely without some statistically significant intransitivities in either the probabilities or gross flows. The regions involved in intransitivities varied greatly from period to period, and only weak evidence indicated lower degrees of intransitivity for local aggregates of regions. The hypothesis of spatially separable utilities must be rejected for the migration data examined. Theoretical discussion indicates that several causes may lead to intransitivities, which in turn lead to problems in applying spatial-interaction models to migration data.

Geologic Interpretation of Radar and Space Imagery of California: ABSTRACT

Side-looking airborne radar (SLAR) imagery in California is interpreted in terms of geologic structure and rock type. Field checks and comparison with published geologic maps indicate some revisions of existing maps. In particular, linears on the radar imagery point to previously unmapped faults. In outcrops where surface texture is related to bedrock lithology, the radar signature may indicate rock type. The unmanned Earth Resources Technology Satellite (ERTS) telemeters multispectral-scanner imagery that is reconstituted into reflected-infrared-color imagery. With respect to radar imagery, the ERTS imagery has poorer spatial resolution and smaller scale; nevertheless, useful regional patterns may be interpreted. Repetition of ERTS imagery on an 18-day cycle should enable us to determine the season for obtaining maximum geologic information. End_of_Article - Last_Page 802------------

Navigation, Field Operation, and Image-Processing Techniques for Thermal Infrared Imagery Surveys: ABSTRACT

Numerous reports have demonstrated the applicability of thermal infrared imagery surveys to geologic, environmental, and agricultural problems. Most thermal infrared imaging for geologic purposes is flown at night to avoid the effects of differential solar heating. Existing aeronautical navigation aids are designed for point-to-point flights rather than the precisely spaced and oriented parallel flight lines required to cover a project area. The traditional method of navigating nighttime imagery flights requires personnel with signal lights to occupy a sequence of ground control points and this method has numerous drawbacks. A newly developed aircraft navigation system utilizes the 9 very low-frequency U.S. Navy radio transmitters located around the globe to fly very accurate courses with no ground aids. Using this system at night to navigate from the base air strip to a known starting point within the project area, parallel survey lines up to 50 mi long have been flown with precise spacing to obtain the necessary imagery sidelap for preparing mosaics. Comparison of actual aircraft flight lines (obtained by plotting nadir line of imagery onto a map) with the programmed flight lines indicates a satisfactory agreement. The navigation system also provides real-time readout of true ground speed which is essential for processing of imagery magnetic tapes. After solving the navigation problems, the flight program is designed. Each project area has unique combinations of terrain and geology that require special consideration, but some generally valid concepts have been established. Normally the orientation of the structural grain of an area is known before the survey. Flight lines should not cross the structural grain at right angles because subtle linear patterns may be obscured by the closely spaced scan lines on the imagery. Selection of flight altitude above average terrain elevation is a tradeoff between imagery spatial resolution versus imagery scale and ground coverage. Cost is also a factor, for at higher flight altitudes the ground coverage is greater and fewer flight lines are required. Atmospheric attenuation of the infrared s gnal at higher flight altitudes must also be considered. As a practical guide to altitude selection, imagery of the same flight line at altitudes ranging from 1,000 to 8,000 ft above terrain is shown. Thermal infrared imagery has been improved greatly by recent advances in electro-optical technology and solid-state physics. Doped germanium detectors which required closed cycle cryostats or liquid helium cooling have been replaced with tri-metal detectors which operate with simple liquid nitrogen cooling to obtain imagery in the 8-14 micrometer wavelength region of greatest geologic significance. Quantitative scanners are now available in which gray-scale variations are calibrated to exact temperature values rather than relative temperature variations. Early airborne scanners which recorded imagery directly on film had many disadvantages. Modern scanners record the imagery on magnetic tape which is later played back onto film in the laboratory. The magnetic tape may be replayed to obtain optimum imagery contrast and to adjust the scale for any variations in aircraft ground speed. Conventional scanner imagery is compressed and distorted at the margins because of the geometry of the system. The magnetic tapes, however, may be processed with a secant-square function to produce rectilinearized imagery with constant scales in the X and Y directions. Various image enhancement techniques also may be applied to the tapes, such as level slicing, digitizing, and conversion to color display for greater resolution of subtle thermal differences. /P> End_of_Article - Last_Page 651------------

Characteristic γ- and X-radiation in the planetary system

Passive observation of the naturally occurring γ-ray and X-ray from the planets is potentially an important technique for determining their gross chemical composition and on the basis of natural γ-radiation determining if the planetary surface is composed of differential material. If the planet is not covered by a thick atmosphere then it is possible to map the distribution of the most abundant elements on a scale of spatial resolution that is of the order of the altitude at which the observations are made. Initial observations carried out from lunar orbit have shown that the flux levels are approximately as expected and that the lunar surface is not characterized by any widespread distribution of acidic rocks in the region observed by the Luna 10 spacecraft.