Rough Earth Research Articles

Augmented RF Propagation Modeling

High-speed, accurate RF propagation models are essential for interference prediction between different spectrum users. We propose a simple and effective regression-based estimation method that can be used both for correcting errors in existing propagation models, such as the Terrain Integrated Rough Earth Model (TIREM), and also as a stand-alone empirical propagation model where no prior model is required. A neural network regression model (NNRM) that is informed by real-world channel and propagation characteristics is developed to obtain accurate path loss predictions throughout a 2.9 km by 2.6 km map of the University of Utah. The proposed NNRM is trained and tested on three path loss measurement campaign data sets collected across the campus, resulting in a 58% to 87% reduction in loss difference variance when used to correct TIREM, and a 59% to 76% reduction in measured signal strength variance when used as an empirical propagation model.

Preliminary analysis of experimental cross-polarization images from polarimetric aircraft synthetic aperture radar of P-band

An analysis of polarimetric synthetic aperture radar (SAR) space observations usage for measuring Faraday rotation angle of plane-polarized electromagnetic radiation on the satellite-Earth-satellite route and calibrating the radar is performed. It is shown that technical characteristics of SAR, the radar movement during the survey and features of electromagnetic waves reflection from the rough Earth’s surface, as well as small-scale ionospheric inhomogeneities affect the results of comparison the radar images at HV and VH cross-polarizations. As a result, there is a problem of SAR signal polarization plane Faraday rotation angle measuring accuracy, which is needed for proper calibration of linearly polarized polarimetric long-wave band SAR using methods proposed by soviet and foreign specialists. Currently, there are no studies of Earth’s surfaces reflection properties carried out by means of space-based long-wave band polarimetric synthesized aperture radars at HV and VH polarizations. At the same time, the authors are not aware of any works, in which the reciprocity principle of cross-polarized HV and VH radar images is analyzed. An attempt to use aircraft P-band radar images at HV and VH polarizations for studying the reciprocity principle is performed in this work.

Мощность лазерного локационного сигнала, отраженного от неровной земной поверхности в условиях замутненной атмосферы

Мощность лазерного локационного сигнала, отраженного от неровной земной поверхности в условиях замутненной атмосферы

Characterization and Significance of Sexually Dimorphic Gape in the Rough Earth Snake,Virginia striatula

The availability of a large morphometric data set from over 2,000 specimens of Virginia presented the opportunity to examine gape dimorphism within V. striatula and its potential adaptive significance in greater detail within this specialist species. In V. striatula, females attain a larger SVL. Gape was strongly associated with increasing SVL in both males and females. Males have significantly larger gapes at all but the shortest SVLs and the dimorphism becomes significant ca 145mm SVL which correlates with sexual maturity. The observed dimorphism is hypothesized to allow males to utilize a wider range of prey (earthworm) sizes at any SVL in order to successfully compete with females for the resource. This would be of particular importance to male fitness during years in which significant drought limits availability of prey.

Analysis on Bidirectional Reflectance Distribution Function of Rough Earth Surface in Remote Sensing Imaging

In remote sensing imaging, bidirectional reflectance distribution function (BRDF) is powerful tool to describe light reflectance characteristic. Based on BRDF distribution of ground object, reflectance distribution in all directions will be calculated, and radiation difference of remote sensing imaging can be calibrated. This paper analyzes the several empirical / semi-empirical BRDF model suitable for the rough earth surface. The cement ground was selected as typical experiment topography, and the ground reflectance in all directions at different solar zenith angle was obtained. We compare measurement data to calculation results of three theoretical models, including five parameter model, Staylor & Suttles model and Walthall model, and analyze and evaluate effectiveness of various models.

Aspects of the Ecology of the Earth Snakes (Virginia valeriae and V. striatula) in the Upper Coastal Plain

Relatively little is known about the ecology and population biology of Virginia striatula (Rough Earth Snake) and Virginia valeriae (Smooth Earth Snake), especially in the southeastern portion of their geographic ranges. We studied populations of the two species on the Savannah River Site (SRS) in Aiken, SC from 1971 to 2007. We found sexual size dimorphism in both species, in which females were longer and heavier than males, but had relatively shorter tails. Overall, Rough Earth Snakes were longer and heavier than Smooth Earth Snakes, but maximum sizes of both species were smaller on the SRS than at other localities from which data are reported. Additionally, all gravid female Smooth Earth Snakes that we captured on the SRS were smaller than their reported size at sexual maturity from other parts of their range. Seasonal activity of Smooth Earth Snakes peaked in May and October, but both Smooth Earth Snakes and Rough Earth Snakes were frequently captured during all warm months. Distinct age classes in the two species were not readily apparent other than several neonates that we captured. We strongly encourage future studies to determine growth rates, longevity, and minimum size at sexual maturity of earth snakes in the Southeast.

Some Features of Electromagnetic Wave Scattering from Statistically Rough Land Covers in the Millimeter-Wave Range of Wavelengths

We present the results of numerical simulation of scattering of millimeter electromagnetic waves from a statistically rough earth surface by the methods of small perturbations and tangent surfaces. We develop numerical algorithms and codes for (i) calculation of the specific effective area of scattering from small-scale, large-scale, and combined (two-scale) structures of land-surface irregularities and (ii) calculation of the field scattered from a rough surface with allowance for the antenna pattern. As an example, we present the results of numerical calculation of the specific effective area of scattering and the scattered field for the case of the Gaussian single-lobe antenna pattern and a land-surface model (asphalt, concrete, sand, and snow) in the form of a periodic structure. The theoretical results obtained for the specific effective area scattering are in good agreement with the experimental data.

Description of the oöcysts of two new species of Eimeria (Apicomplexa: Eimeriidae) from the rough earth snake Virginia striatula (Serpentes: Colubridae) in Texas and Arkansas

Coccidian oocysts recovered from the faeces of rough earth snakes Virginia striatula (Serpentes: Colubridae) were found to represent two previously unreported eimerians. Oocysts of Eimeria desotoensis n. sp. were found in 5/32 (16%) of the snakes and were spherical to ellipsoidal, 18.4 × 17.2 (15–21.5 × 15–19.5) μm, with a thin, single-layered wall; their shape-index (length/width) was 1.07 (1.00–1.23). A micropyle and oocyst residuum were absent; polar granule were present in 33% of the oocysts. The sporocysts were ovoidal, 11.5 × 7.6 (10.5–13 × 7–8) μm, with a Stieda body; their shape-index was 1.51 (1.30–1.68). The sporocyst residuum was moderate in size and composed of a cluster of granules. Oocysts of Eimeria hobartsmithi n. sp. were found in 2/32 (6%) of the snakes and were subspherical to ellipsoidal, 18.0 × 15.7 (16–20 × 15–17) μm, with a thin, single-layered wall; their shape-index was 1.15 (1.02–1.32). A micropyle, oocyst residuum and polar granule were absent. The sporocysts were elongate, 13.2 × 6.3 (12–14.5 × 6–6.5) μm, with a Stieda body; their shape-index was 2.10 (1.88–2.34). A large sporocyst residuum was present in each sporocyst, often obscuring the sporozoites. In addition to the two new species, oocysts of E. striatula Upton & McAllister, 1990 were observed in 38% of the snakes.

Propagation in a surface duct over a two‐dimensional sinusoidal rough Earth

A solution for the problem of horizontally polarized radio waves propagating in a surface duct situated over a perfectly conducting, sinusoidally shaped ground with small amplitudes is obtained. The solution contains the assumption that the source is a horizontal line source perpendicular to the roughness variation. It is found that the specular contribution may be derived using an equivalent matrix with an effective reflection coefficient that accounts for scattering both out of and into the specular direction. The accuracy of a method for obtaining the rough Earth waveguide eigenvalues as a perturbation of those for the smooth Earth case is analyzed. Numerical field results are compared using the different approaches, demonstrating an attenuation effect due to the roughness.

Responses to snake odors by laboratory mice

Male and female laboratory mice ( Mus musculus ; Harlan Sprague Dawley) were tested for reactions to snake odors. In the first experiment, mice were presented with untreated paper on the floor of one side of a test tank and snake-scented or control (water misted) paper on the other side. The scented papers were obtained from rough earth snakes ( Virginia striatula ), which were fed earthworms, and a rat snake ( Elaphe obsoleta ), which ate mice. Male mice exhibited no differences in response to the three conditions. Female mice showed no response to the control or earth snake odor, but they deposited significantly more fecal boli on the side of the tank with the rat snake odor than on the blank side. No significant differences in other behaviors, e.g. ambulation, were detected. In the second experiment, female mice were offered food pellets treated with the shed skin extract of the rat snake or with a solvent alone. Less material was bit off and consumed from the snake-scented pellets. The results of both experiments indicate that female mice detect the odors of rat snakes.

SEKE: A computer model for low altitude radar propagation over irregular terrain

SEKE, a new site-specific propagation model for general terrain, makes use of the original Lincoln Laboratory models geometrical optics (GOPT), low altitude propagation spherical earth (LAPSE), and low altitude propagation knife edges (LAPKE) to compute multipath, spherical earth diffraction, and multiple knife-edge diffraction losses. The proper algorithm is selected based on terrain geometry, antenna and target heights, and frequency. Comparison of model predictions with measurements over several paths ranging from level to rough at five frequencies ( <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">X</tex> -band through VHF) is presented. A brief discussion on the performance of SEKE over general terrain with respect to the expected performance of the two other general terrain-specific models (Longley-Rice and terrain integrated rough earth model (TIREM)) is given.

The Angular Spread of Radio Waves in Long‐Distance Ionospheric Propagation

A simple solution of the problem of scattering of radio waves in successive encounters with a rough earth and an ionosphere which introduces irregularities into the phase is presented. This leads to calculated shapes of the incoming angular power spectrum and of the antipodal area and indicates that, under some special circumstances, an antipodal circle of enhanced signal strength may also be present. Some comparisons are made with a few experimental results.