Sensitivity of GNSS-R spaceborne observations to soil moisture and vegetation

Global navigation satellite systems-reflectometry (GNSS-R) is an emerging remote sensing technique that makes use of navigation signals as signals of opportunity in a multistatic radar configuration, with as many transmitters as navigation satellites are in view. GNSS-R sensitivity to soil moisture has already been proven from ground-based and airborne experiments, but studies using space-borne data are still preliminary due to the limited amount of data, collocation, footprint heterogeneity, etc. This study presents a sensitivity study of TechDemoSat-1 GNSS-R data to soil moisture over different types of surfaces (i.e., vegetation covers) and for a wide range of soil moisture and normalized difference vegetation index (NDVI) values. Despite the scattering in the data, which can be largely attributed to the delay-Doppler maps peak variance, the temporal and spatial (footprint size) collocation mismatch with the SMOS soil moisture, and MODIS NDVI vegetation data, and land use data, experimental results for low NDVI values show a large sensitivity to soil moisture and a relatively good Pearson correlation coefficient. As the vegetation cover increases (NDVI increases) the reflectivity, the sensitivity to soil moisture and the Pearson correlation coefficient decreases, but it is still significant.Postprint (author's final draft

An integrated geodetic and InSAR technique for the monitoring and detection of active faulting in southwestern Sicily

We present the results of the analysis of GNSS (Global Navigation Satellite System) and InSAR (Interferometric synthetic-aperture radar) data collected in the frame of a project financed by the “Struttura Terremoti” of INGV (Istituto Nazionale di Geofisica e Vulcanologia). Combined investigations pointed out for potential seismogenic sources for destructive earthquakes recorded in southwestern Sicily, including the 1968 Belice earthquake sequence and that supposed to have destroyed the Greek city of Selinunte which, according to geoarcheological data experienced two earthquakes in historical times. Our approach is aimed to evaluate the current deformation rate in SW Sicily and to improve the knowledge about the seismic potential of this area. The geodetic data proposed in this paper show that the Campobello di Mazara–Castelvetrano alignment (CCA) is currently deforming with a vertical and horizontal displacements of 2 mm/yr and 0.5 mm/yr respectively, according to the tectonic setting of the are

Technologies and solutions for location-based services in smart cities: past, present, and future

Location-based services (LBS) in smart cities have drastically altered the way cities operate, giving a new dimension to the life of citizens. LBS rely on location of a device, where proximity estimation remains at its core. The applications of LBS range from social networking and marketing to vehicle-toeverything communications. In many of these applications, there is an increasing need and trend to learn the physical distance between nearby devices. This paper elaborates upon the current needs of proximity estimation in LBS and compares them against the available Localization and Proximity (LP) finding technologies (LP technologies in short). These technologies are compared for their accuracies and performance based on various different parameters, including latency, energy consumption, security, complexity, and throughput. Hereafter, a classification of these technologies, based on various different smart city applications, is presented. Finally, we discuss some emerging LP technologies that enable proximity estimation in LBS and present some future research areas

First results of a GNSS-R experiment from a stratospheric balloon over boreal forests

The empirical results of a global navigation satellite systems reflectometry (GNSS-R) experiment onboard the Balloon EXperiments for University Students (BEXUS) 17 stratospheric balloon performed north of Sweden over boreal forests show that the power of the reflected signals is nearly independent of the platform height for a high coherent integration time T-c = 20 ms. This experimental evidence shows a strong coherent component in the forward scattered signal, as compared with the incoherent component, that allows to be tracked. The bistatic coherent reflectivity is also evaluated as a function of the elevation angle, showing a decrease of similar to 6 dB when the elevation angle increases from 35. to 70 degrees. The received power presents a clearly multimodal behavior, which also suggests that the coherent scattering component may be taking place in different forest elements, i.e., soil, canopy, and through multiple reflections canopy-soil and soil-trunk. This experiment has provided the first GNSS-R data set over boreal forests. The evaluation of these results can be useful for the feasibility study of this technique to perform biomass monitoring that is a key factor to analyze the carbon cycle.Peer ReviewedPostprint (author's final draft

Analysis of Precipitable Water Vapour in Nigeria using GNSS Observations

Water Vapour estimation using ground-based Global Navigation Satellite System (GNSS) observations is a well-established technology that contributes to weather forecast, research, and climate monitoring. Water vapour in the atmosphere is directly related with precipitation that may lead to extreme event (e.g., floods). The application of GNSS to sense the total amount of water vapour integrated along the signal path in the troposphere is what is referred to as GNSS meteorology. GNSS has the advantage of all-weather condition, low cost with high temporal and spatial resolution when compared to other classical methods of water vapour measuring that are expensive and/or with low spatial and temporal coverage. When GNSS signals are transmitted from GNSS satellites in space to ground-based GNSS receivers, they experience a tropospheric delay (an error source in GNSS positioning) often represented in GNSS meteorology as the Zenith Total Delay (ZTD). The ZTD is the sum of the Zenith Hydrostatic Delay and the Zenith Wet Delay and it is one of the products of GNSS data processing. The ZTD can be converted to Precipitable Water Vapour (PWV) when surface temperature and pressure values are known at the GNSS site using a conversion factor (?) that is dependent on the weighted mean temperature (Tm) and pressure. This dissertation focuses on the estimation and analysis of water vapour in Nigeria using GNSS observations. The Nigerian Permanent GNSS Network (NIGNET) stations observations and products were retrieved from the infrastructure implemented by Office of the Surveyor General of the Federation (OSGoF). Processing of the data was carried out using online software (GipsyX) for the estimation of ZTD. Fifteen GNSS stations were used in this research and the period 2009 to 2021 was considered. The characteristics of the ZTD over the territory of Nigeria was investigated. The range of ZTD variation in Nigeria for the period used in this research was found to be approximately between 1900mm to 2700mm in the NIGNET stations. The two main seasons in Nigeria were significantly noticed as low peaks were found to be occurring during the dry (winter) season while high peaks were remarkably seen during the rainy (summer) season. The amplitude of the seasonal variation within the period under investigation is between a minimum of 36mm to a maximum of 124mm with the Northern region having higher values than the Southern part. It was discovered ultimately by the results obtained from the analyses, that ZTD variation in both the Northern and Southern regions are influenced by the 4 distinct climates and other local weather conditions including temperature and the trade wind from Sahara Desert and the Atlantic Ocean.A estimativa de vapor de água usando observações do Sistema Global de Navegação por Satélite (GNSS) é uma tecnologia bem estabelecida que tem dado um contributo importante para a realização de previsões meteorológicas, investigação e monitorização climática. O vapor de água na atmosfera está diretamente relacionado com a precipitação que pode levar a eventos extremos (por exemplo, inundações). A área de estudo do uso de dados GNSS para detetar a quantidade total de vapor de água integrado ao longo do caminho do sinal na troposfera é designado de meteorologia GNSS. O GNSS tem como vantagem de poder ser utilizado em todas as condições climáticas, apresentar baixo custo e alta resolução temporal e espacial quando comparado a outros métodos clássicos de medição de vapor de água, normalmente mais caros e/ou com baixa cobertura espacial e temporal. Quando os sinais GNSS são transmitidos dose satélites para recetores terrestres, existe um atraso troposférico (uma fonte de erro no posicionamento GNSS) frequentemente representado na meteorologia GNSS como o Atraso Zenital Total (ZTD em Inglês ). O ZTD é a soma do Atraso Zenital e do Atraso Zenital Húmido e é um dos produtos do processamento de dados GNSS. O ZTD pode ser convertido em PWV quando os valores de temperatura e pressão da superfície são conhecidos no local através de um fator de conversão (?) que depende da temperatura média ponderada (Tm) e da pressão. Esta dissertação tem como objetivo a estimativa e análise de vapor de água na Nigéria usando observações GNSS. As observações e produtos das estações da Rede Permanente GNSS da Nigéria (NIGNET) foram obtidos através da infraestrutura implementada pelo OSGoF. O processamento dos dados foi realizado por meio de software online (GipsyX) para a estimativa do ZTD. Dados de quinze estações GNSS foram utilizadas na análise correspondendo ao período entre 2009 a 2021, para avaliar as características da ZTD sobre o território da Nigéria. A faixa de variação de ZTD na Nigéria para o período considerado foi de aproximadamente 1900mm a 2700mm nas estações NIGNET. As duas principais estações climáticas na Nigéria destacaram-se, com picos baixos que ocorreram durante a estação seca (inverno), e picos altos observados durante a estação chuvosa (verão). A amplitude da variação sazonal no período sob investigação é entre um mínimo de 36mm e um máximo de 124mm com a região norte tendo valores mais elevados que a região sul. Pelos resultados obtidos das análises foi ainda possível verificar que a variação da ZTD nas regiões Norte e Sul são influenciadas pelos 4 climas distintos e outras condições climáticas locais, incluindo temperatura e ventos alísios do deserto do Saara e do Oceano Atlântico

Global navigation satellite system (GNSS): a utility for sustainable development in Ghana

The rapid spread of modern information and communication technologies (ICT) is dependent on the unprecedented increase in information relating to our natural, economic and social environment, and for Ghana and Africa to be in tune with the current trends in ICT, spatial information and methods to acquire them should be our priority. GNSS is therefore the obvious choice. This technology has an enormous potential to contribute to the management of environment, natural disasters, provide food security, emergency response, improve the efficiency in surveying and mapping. Land, water and air navigation will undergo a dramatic improvement with the application of GNSS. This is just to mention a few of the expected benefits. This paper focuses on the benefits to be derived by Ghana as a developing country and Africa in general from the introduction of a functional Multipurpose Global Navigation Satellite System. It specifically highlights the needed basic infrastructure for setting up a Continuously Operating reference System and the need for acquiring the necessary infrastructure to utilize the European Satellite-Based Augmentation System (SBAS), EGNOS. Areas of probable application and benefits have been outlined and the necessary considerations for a successful implementation and its sustenance have been suggested. It looks at how this space technology can support our sustainable development as developing nations.Journal of Science and Technology (Ghana) Vol. 27 (2) 2007: pp. 130-13

EURO-AFRICA SPACE. EXPLORING THE POTENTIALS, OVERCOMING CHALLENGES IN EU-AFRICA SPACE ECONOMY.

openLe tecnologie e le applicazioni spaziali svolgono un ruolo essenziale nella nostra vita e nell’economia globale, anche se il loro ruolo, molto importante, non viene spesso riconosciuto. Con la crescente domanda di servizi spaziali in vari settori, Europa e Africa hanno riconosciuto l’importanza di promuovere la cooperazione e la collaborazione nell’industria spaziale. La tesi esplora questa partnership, il potenziale e le sfide nell'economia spaziale UE-Africa. Esamina lo stato attuale dell’economia spaziale UE-Africa, identificando le sfide che ne ostacolano la crescita ed esplorando il potenziale non sfruttato per lo sviluppo reciproco. Inoltre, esamina le capacità tecnologiche e le infrastrutture esistenti in Africa, evidenziando le aree che possono trarre vantaggio dal trasferimento di conoscenze e dalle iniziative di rafforzamento delle capacità. La cooperazione UE-Africa, che esiste da oltre mezzo secolo, può svolgere un ruolo significativo nel contribuire ad affrontare queste sfide. Il partenariato può facilitare l’accesso alle risorse finanziarie e tecnologiche, il trasferimento di tecnologia e la promozione di opportunità commerciali e di investimento. Pertanto, la cooperazione UE-Africa può sbloccare il potenziale dell’economia spaziale in Africa, creando crescita economica e opportunità per la popolazione del continente. Attraverso un'ampia revisione della letteratura, studi di casi, analisi specifiche per paese e un'analisi SWOT, le domande di ricerca ruotano attorno a questi problemi, con l'intenzione di identificare le lacune nella conoscenza e le priorità di ricerca per studi futuri. Per affrontare le sfide identificate, la tesi propone raccomandazioni e strategie per promuovere la collaborazione UE-Africa nell’economia spaziale. Sottolinea la necessità di maggiori investimenti nelle infrastrutture e nel capitale umano e nella creazione di piattaforme per il dialogo e la cooperazione per promuovere lo sviluppo sostenibile e socioeconomico in entrambe le regioni.Space technologies and applications play an essential role in our daily lives and the global economy, even though their important role often goes unseen. With the growing demand for space-based services in various sectors, Europe and Africa have recognized the importance of fostering cooperation and collaboration in the space industry. The dissertation explores this partnership, the potential, and the challenges in the EU-Africa space economy. It examines the current state of the EU-Africa space economy, identifying the challenges that hinder its growth and exploring the untapped potential for mutual development. Additionally, it investigates the existing technological capabilities and infrastructure in Africa, highlighting areas that can benefit from knowledge transfer and capacity-building initiatives. EU-Africa cooperation, which has existed for over half a century, can play a significant role in helping to address these challenges. The partnership can facilitate access to financial and technical resources, the transfer of technology, and the promotion of trade and investment opportunities. Thus, EU-Africa cooperation can unlock the potential of the Space Economy in Africa, creating economic growth and opportunities for the continent's people. Through an extensive literature review, case studies, country-specific analysis, and a SWOT analysis, research questions revolve around these issues, intending to identify gaps in knowledge and research priorities for future studies. To address the identified challenges, the dissertation proposes policy recommendations and strategies to foster EU-Africa collaboration in the space economy. It emphasizes the need for increased investment in infrastructure and human capital and establishing platforms for dialogue and cooperation to promote sustainable and socio–economic development in both regions