scholarly journals Impact of spatial averaging on radar reflectivity at internal snowpack layer boundaries

2016 ◽  
Vol 62 (236) ◽  
pp. 1065-1074 ◽  
Author(s):  
N. RUTTER ◽  
H.-P. MARSHALL ◽  
K. TAPE ◽  
R. ESSERY ◽  
J. KING
Keyword(s):  
Continuous Wave ◽  
Microwave Remote Sensing ◽  
Surface Scattering ◽  
Spatial Averaging ◽  
Microwave Radar ◽  
Snow Stratigraphy ◽  
Wave Radar ◽  
Snowpack Properties ◽  
The Impact

ABSTRACTMicrowave radar amplitude within a snowpack can be strongly influenced by spatial variability of internal layer boundaries. We quantify the impact of spatial averaging of snow stratigraphy and physical snowpack properties on surface scattering from near-nadir frequency-modulated continuous-wave radar at 12–18 GHz. Relative permittivity, density, grain size and stratigraphic boundaries were measured in-situ at high resolution along the length of a 9 m snow trench. An optimal range of horizontal averaging (4–6 m) was identified to attribute variations in surface scattering at layer boundaries to dielectric contrasts estimated from centimetre-scale measurements of snowpack stratigraphy and bulk layer properties. Single vertical profiles of snowpack properties seldom captured the complex local variability influencing near-nadir radar surface scattering. We discuss implications of scaling in-situ measurements for snow radiative transfer modelling and evaluation of airborne microwave remote sensing of snow.

scholarly journals Cyclostationary-Based Vital Signs Detection Using Microwave Radar at 2.5 GHz

Sensors ◽  
2020 ◽  
Vol 20 (12) ◽  
pp. 3396
Author(s):  
Fatima Sekak ◽  
Kawtar Zerhouni ◽  
Fouzia Elbahhar ◽  
Madjid Haddad ◽  
Christophe Loyez ◽  
...  
Keyword(s):  
Continuous Wave ◽  
Vital Signs ◽  
The Body ◽  
Contact Detection ◽  
Body Movements ◽  
Non Invasive ◽  
Microwave Radar ◽  
Reflected Signal ◽  
The Impact ◽  
Invasive Measurement

Non-contact detection and estimation of vital signs such as respiratory and cardiac frequencies is a powerful tool for surveillance applications. In particular, the continuous wave bio-radar has been widely investigated to determine the physiological parameters in a non-contact manner. Since the RF-reflected signal from the human body is corrupted by noise and random body movements, traditional Fourier analysis fails to detect the heart and breathing frequencies. In this effort, cyclostationary analysis has been used to improve the radar performance for non-invasive measurement of respiratory rate and heart rate. However, the preliminary works focus only on one frequency and do not include the impact of attenuation and random movement of the body in the analysis. Hence in this paper, we evaluate the impact of distance and noise on the cyclic features of the reflected signal. Furthermore, we explore the assessment of second order cyclostationary signal processing performance by developing the cyclic mean, the conjugate cyclic autocorrelation and the cyclic cumulant. In addition, the analysis is carried out using a reduced number of samples to reduce the response time. Implementation of the cyclostationary technique using a bi-static radar configuration at 2.5 GHz is shown as an example to demonstrate the proposed approach.

Accuracy Analysis of Positioning Method for Fusion GPS Pseudo-Range and Continuous Wave Radar

2013 ◽  
Vol 756-759 ◽  
pp. 354-360
Author(s):  
Hui Juan Zhang ◽  
Chao Wei
Keyword(s):  
Continuous Wave ◽  
Calculated Data ◽  
Wave Radar ◽  
Global Positioning ◽  
Positioning Method ◽  
Measurement Principle ◽  
Trajectory Measurement ◽  
The Impact ◽  
Cw Radar ◽  
Range Test

Continuous wave (CW) radar and global positioning system (GPS) is the main equipment of trajectory measurement in range. Based on range test background, propose a method to fuse GPS pseudo-range and CW radar range to provide complete trajectory positioning parameters, effectively reduce the impact of the systematic error of the measuring element to improve positioning precision of aircraft orbit solving. Through research on the measurement principle and the practice calculated data is given in this paper. Finally, several famous practical examples and simulation results are presented to illustrate our method efficiently.

scholarly journals On the Low Frequency Impact Noise Measurement in Residential Buildings

2021 ◽  
Vol 2069 (1) ◽  
pp. 012159
Author(s):  
D Urbán ◽  
P Zat’ko
Keyword(s):  
Acoustic Pressure ◽  
Residential Buildings ◽  
Low Frequency ◽  
Spatial Averaging ◽  
Impact Noise ◽  
Normative Requirements ◽  
Enclosed Space ◽  
The Cost ◽  
The Impact

Abstract We commonly encounter cases that, despite the fact that buildings meet normative requirements, people are disturbed by unwanted noise generated by walking and other sources of impact noise. It is not unusual that in practice the designer often moves on the edge of the required criteria in order to reduce the cost of constructions and its parts. In this article, we selected 4 blindly chosen cases of flats where complaints from residents about high levels of impact noise were recorded although the construction meets the requirements set out in the standard. Based on the obtained documentation of in-situ performed measurements by different consulting companies, BEM and FEM models were created, and the distribution of acoustic pressure in an enclosed space and compared different methods of spatial averaging of the resulting acoustic pressure were simulated. The aim of this analysis is to point some of the reasons for possible user complaints about the impact noise despite normative requirements. The usual problems are benevolent national requirements and the issue of measuring noise in the low frequency range and underestimating its significance. The article also discusses the currently set requirements for the evaluation of floor structures in selected countries.

Impact of variability in measured and simulated tundra snowpack properties on heat transfer metrics

2021 ◽  
Author(s):  
Victoria Dutch ◽  
Nick Rutter ◽  
Leanne Wake ◽  
Mel Sandells ◽  
Chris Derksen ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Spatial Variability ◽  
Spatial Scales ◽  
Field Measurements ◽  
Density Profiles ◽  
Community Land Model ◽  
Spatially Distributed ◽  
Snowpack Properties ◽  
The Impact

<p>Tundra snowpack properties are highly heterogenous over a variety of spatial scales and evolve over the course of the winter. Variations in snowpack properties such as snow density and microstructure control the transfer of heat through the snowpack. Thermal properties of the snowpack impact the subnivean environment; snow insulates the underlying soil, allowing films of liquid water to remain unfrozen, enabling biological processes to take place. In this study, field measurements from four field campaigns across two different winters (March and November 2018, January and March 2019) are used to capture and constrain the spatial variability of the snowpack. These include 1050 spatially distributed Snow MicroPenetrometer (SMP) profiles throughout the Trail Valley Creek catchment in the Northwest Territories, Canada. Bespoke coefficients for tundra snowpacks were calculated (based on the work of King et al., 2020) to convert raw SMP force measurements to densities. This allowed density changes of vertical profiles to be assessed and spatial variability in the thickness and properties of three snowpack layers (wind slab, indurated hoar and depth hoar) to be quantified. 105 needleprobe measurements from 37 snowpits were used to contrast the density and thermal conductivity of snowpack layers, as well as thermal conductivities estimated from recalibrated SMP density profiles. These in-situ measurements will be compared to 1-D simulations of snowpack properties from the Community Land Model (PTCLM 5.0) over the two winter seasons. The impact of snowpack layering on snow heat transfer metrics will be investigated using both 2-layer (wind slab: depth hoar) and 3-layer (wind slab: indurated hoar: depth hoar) snowpack configurations. The spatial variability of heat transfer metrics across the Trail Valley Creek catchment will also be considered.</p>

scholarly journals Estimating alpine snowpack properties using FMCW radar

2005 ◽  
Vol 40 ◽  
pp. 157-162 ◽  
Author(s):  
Hans-Peter Marshall ◽  
Gary Koh ◽  
Richard R. Forster
Keyword(s):  
Continuous Wave ◽  
Snow Water Equivalent ◽  
Radar Data ◽  
Average Density ◽  
Electrical Measurements ◽  
Large Spatial Scale ◽  
Promising Alternative ◽  
Fmcw Radar ◽  
Snowpack Properties

AbstractLarge variations in both snow water equivalent (SWE) and snow slope stability are known to exist in the alpine snowpack, caused by wind, topographic and microclimatic effects. This variability makes extrapolation of point measurements of snowpack properties difficult and prone to error, but these types of measurements are used to estimate SWE and stability across entire mountain ranges. Radar technology provides a promising alternative to point measurements, because large areas can be covered quickly and non-intrusively. There is great potential for obtaining information on a large spatial scale from airborne applications. Frequency-modulated continuous wave (FMCW) radar measurements were made from the ground in several different alpine snowpacks, along with manual and in situ electrical measurements. The surface and ground reflections from the radar data, combined with an average density estimate, can provide a useful estimate of SWE. In addition, the locations of internal reflections are highly correlated with both visually identified layers and measured changes in in situ dielectric properties.

scholarly journals Range-speed mapping and target-classification measurements of automotive targets using photonic-radar

2020 ◽  
Vol 52 (10) ◽  
Author(s):  
Vishal Sharma ◽  
Sergey Sergeyev ◽  
Love Kumar ◽  
Hani J. Kbashi
Keyword(s):  
Autonomous Vehicles ◽  
Continuous Wave ◽  
Target Identification ◽  
Autonomous Vehicle ◽  
Vertical Axis ◽  
Input Power ◽  
Target Range ◽  
Target Velocity ◽  
Microwave Radar ◽  
Wave Radar

Abstract The frequency-modulated continuous-wave radar is an ideal choice for autonomous vehicle and surveillance-related industries due to its ability to measure the relative target-velocity, target-range, and target-characterization. Unlike conventional microwave radar systems, the photonic radar has the potential to offer wider bandwidth to attain high range-resolution at low input power requirements. Subsequently, a frequency-modulated continuous-wave photonic-radar is developed to measure the target-range and velocity of the automotive mobile targets concurrently with acceptable rang resolution keeping in mind the needs of the state-of-the-art autonomous vehicle industry. Furthermore, the target-identification is also an important parameter to be measured to enable the futuristic autonomous vehicles for the recognition of the objects along with their dimensions. Therefore, the reported work is extended to characterize the target-objects by measuring the specular-reflectance, diffuse-reflectance, the ratio of horizontal-axis to vertical-axis, refractive index constants of the targets using the bidirectional reflectance distribution function. Furthermore, the reflectance properties of the target-objects are also measured with different operating wavelengths at different incident angles to assess the influence of the operating wavelength and the angle at which the radar-pulses incident on the surface of the targets. Moreover, to validate the performance of the demonstrated work, a comparison is also presented in distinction with the conventional microwave FMCW-RADAR.

scholarly journals Simulation of microwave emission from physically modeled snowpacks

2000 ◽  
Vol 31 ◽  
pp. 397-405 ◽  
Author(s):  
Andreas Wiesmann ◽  
Charles Fierz ◽  
Christian Mätzler
Keyword(s):  
Microwave Radiation ◽  
Meteorological Data ◽  
High Sensitivity ◽  
Microwave Remote Sensing ◽  
Microwave Emission ◽  
Detailed Knowledge ◽  
Emission Model ◽  
Snowpack Properties ◽  
Good Agreement

AbstractDetailed knowledge of snowpack properties is crucial for the interpretation and modeling of thermal microwave radiation. Here we use two well-known snow models, Crocus and SNTHERM, to obtain snow profiles from meteorological data. These profiles are compared with pit profiles and used as input to the Microwave Emission Model of Layered Snowpacks (MEMLS) for the simulation of microwave radiation. The snow-profile data can be applied almost directly. Adaptation is needed only in the conversion of the grain-size used in the snow models to the correlation length used in the emission model; it is based on empirical fits. The resulting emissivities are compared with in situ microwave measurements. The computed snow depths are in good agreement with observations. Comparison of selected profiles shows that Crocus is in good agreement with the pit profile, but the density of simulated melt-freeze crusts is underestimated. The SNTHERM profiles show no such crusts, and the density deviates from the pit profiles. The computed temporal behavior of the snowpack emissivity is reasonable. Comparison of selected situations with in situ measurements indicates good agreement. However, the polarization difference tends to be underestimated because of inaccuracies in the simulation of density profiles. The results show the potential of combined snow-physical and microwave-emission models for understanding snow signatures and for developing snow algorithms for microwave remote sensing. Based on the frequency-selective penetration and on the high sensitivity to snow texture, density and wetness, microwave radiometry can offer a new dimension to snow physics. Potential applications are described.

In situ Quantification of the Impact of Episodic Enhanced Turbulent Events in Large Phytoplankton

2011 ◽  
Author(s):  
Percy L. Donaghay ◽  
Jan Rines ◽  
James Sullivan
Keyword(s):  
The Impact
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