Insight into remote monitoring systems

As has been witnessed in the span of a few decades, remote sensing remains one of the key areas of research that deals with distant activities without making physical contact with the object to be sensed. The phenomena of electromagnetics are essentially to be exploited to devise remote sensing systems for various applications. In a broad range of fields, military surveillance, weather prediction systems, geographical measurements, medical diagnostics, smart structure monitoring, global positioning and other communication systems, etc. constitute some of the notable examples [1,2]. Apart from these, several other key areas exist wherein the use of the remote sensing equipment becomes vital.

Remote sensing systems basically work on a data acquisition process in respect of the transmitted and received electromagnetic radiations, the characteristic features of which determine the sensing of measurands and/or objects in the surrounding areas. Inspired by the importance of this technology in scientific investigations and other commercial purposes of everyday use, the joint editors-in-chief of the Journal of Electromagnetic Waves and Applications (JEMWA) give a thought on bringing out a Special Issue – Insight into Remote Monitoring Systems – on this topic. Indeed, JEMWA remains a perfect platform to make abreast of some of the recent findings in this area of research to the valued readers. This Special Issue encapsulates some 11 papers – all pivoted to, in some way or the other, the discussions pivoted to the mechanisms involved in remote sensing systems.

Apart from the household and other commercial applications, remote sensing has been of great deal with the sensor technologies exploited in aircrafts, satellites and radars [3,4]. The phenomenon of scattering of waves remains greatly important in this context as the scattering cross-section of object determines how easily and efficiently it can be detected [5]. References [6–8] discuss the scattering of radiations from certain kinds of objects. The object(s) can be on the Earth or space in any particular form. For example, it may even be buried in certain kinds of mediums. In this stream, El-Ocla proposed a mechanism to remotely sense targets like conducting objects located within continuous random media. In the paper, the author rather investigate on to enhance the accuracy of remote sensing of such objects. The work incorporates numerical analyses of radar cross-section to characterise such mediums considering various external parameters that affect the scattering of waves by the target and surrounding medium. Also, the impact on backscattering due to the variations in random medium characteristics is also evaluated. As an illustrative example, the author highlights the usefulness of study in cases like airplanes facing turbulence.

In another problem, Saddek and Richard touch upon the characterisation of three-dimensional layered structures with an arbitrary number of slightly rough interfaces illuminated by an electromagnetic plane wave. For the analytical approach, using the first-order small perturbation method, the authors estimate the statistical distributions for the co- and cross-polarised scattered intensity ratios in any observation plane. As illustrative examples, they take up four different configurations, such as air/clayey soil/rock with and without a snow cover in the backscattering direction and in two other observation directions. Considering Gaussian spectrum interfaces, the authors analyse the influence of snow cover upon the statistical distributions and validate the results by comparing with those obtained through Monte-Carlo simulations.

The atmospheric condition remains greatly responsible in degrading the signal determination in remote sensing applications. The presence of duct and other impurities essentially affects the electromagnetic waves propagating in the medium primarily because of the variations in the refractive index profile (of the medium). In another work, Tang et al. investigate the influence of atmospheric duct on the performance of wireless communication and radar systems. In this stream, the authors propose a new refractivity profile estimation method based on the signal from an automatic identification system, which is a maritime navigation safety communication system operating in the very high-frequency mobile band. The authors present numerical simulations that demonstrate the proposed method to be feasible for refractivity profile estimation.

Antennas are the basic building blocks of wireless remote sensing systems, as these transmit and receive signals [9]. In a related field, the article by Bui et al. presents a design of low-cost and simple electronically-steerable 2.4 GHz antenna array suitable for indoor positioning systems. They report high gain, low-profile and small beam-width in the steering direction of antenna. Upon performing a series of simulations and experiments, the authors claim the robustness and suitability of the proposed antenna structure for the stated kind of positioning systems. In yet another paper, Casula touches upon the investigation results of a low-cost and miniaturised wearable textile antenna in the UHF frequency band for short-range wireless applications. The features like versatility and robustness make the antenna highly promising for short-range sensing needs.

Radar applications in remote sensing involve the detection of radiation (by a sensor) reflected or backscattered by an object (or target), which determines the interpretation of an image [3]. Within the context, the automatic target recognition remains greatly important in synthetic aperture radar (SAR) systems. This Special Issue incorporates a few papers focused on the investigations related to SAR imaging. In this stream, a paper by Tan et al. proposes the SAR automatic target recognition method based on the matching of target outlines that describe the physical shape and size of target. The reported results are from the experiments conducted on moving and stationary target acquisition and recognition datasets obtained under both the standard and typically extended operating conditions. In another work on the automatic target recognition method of SAR, Miao and Liu present a joint sparse representation of the complementary components from the original SAR image. In the paper, the shadow and target images are generated from the original image, and the authors developed a simple algorithm designed to separate out the shadow. In order to evaluate the proposed method, they also performed experiments on the moving and stationary target acquisition and recognition datasets under various conditions and found encouraging results to prove the proposed method to be effective and robust.

In yet another paper, Miao and Shan present the SAR target recognition method via sparse representations of multi-view images with correlation analysis. The obtained results show the proposed method to be superior over some other previously reported techniques in this context. Also, the article by Ma et al. discusses the issues related to ground target recognition (by radars) owing to the presence of interference due to noise. In their work, the authors develop a framework to deal with the noise interference and target aspect-sensitivity problem for the recognition of ground targets. Simultaneously, the authors present experimental observations in support of the developed framework simulations.

Based on the automatic target recognition systems in radars, Liu and Wang study the simulation and statistical analyses of aircraft models, and propose effective numerical solutions. They consider the dynamic target attitude perturbation as one of the dominant interference factors that affect signal detection, and justify the analyses in terms of efficiency and accuracy to suite well with the practical dynamic target classification.

In target recognition systems, clutter plays an important role in foliage environment. Pivoted to this issue, Lei presents the statistical modeling of foliage clutter in different environments. The author presents models to characterise and parameterise the amplitude of clutter considering illustrative examples of foliage environments having different densities, and finds those advantageous in understanding the involvedmechanisms.

These afore discussed topics relate, somehow or the other, to the sensing mechanisms in certain applications, which can be improvised by suitably implementing the models for signal detection. The proper use of the aspects of electromagnetics remains vital in the development and accuracy of efficient models. JEMWA paved a long way to be recognised as one of the pioneering platforms pivoted to the electromagnetics research from various lexicons [10,11]. Its serving the relevant R&D community for over 30 years essentially reflects the profound feet the Journal has established so far. The current Special Issue – Insight into Remote Monitoring Systems – remains an effort to communicate with readers the discussions on certain important topics under such cover; hopefully the articles will be found interesting.

Disclosure statement

No potential conflict of interest was reported by the authors.