Water quality estimation and mapping in reservoirs using remote sensing techniques: The case study of lake Karla.

106 σ.Σήμερα η ανάγκη παρακολούθησης και προστασίας του περιβάλλοντος είναι πιο έντονη από ποτέ. Παράλληλα, απαραίτητες καθίστανται μέθοδοι και τεχνικές αξιόπιστες και χαμηλού κόστους. Οι σύγχρονες τεχνολογίες και οι μέθοδοι παρακολούθησης του γήινου περιβάλλοντος αποτελούν ένα πολύτιμο εργαλείο προς τη κατεύθυνση αυτή. Στη παρούσα εργασία, κύρια επιδίωξη αποτέλεσε η τυποποίηση της διαδικασίας χαρτογράφησης των βασικών ποιοτικών παραμέτρων παρακολούθησης λιμναίων οικοσυστημάτων. Με συνδυασμό ταυτόχρονων επίγειων και δορυφορικών πολυφασματικών παρατηρήσεων, έγινε προσπάθεια εκτίμησης με τηλεπισκοπικά μέσα των ποιοτικών χαρακτηριστικών του νερού. Δεδομένα αποτέλεσαν οι δορυφορικές εικόνες του Landsat 8, τα υπερφασματικά δεδομένα από φασματογράφο χειρός και τα αποτελέσματα των αντίστοιχων χημικών αναλύσεων, τα οποία αποτέλεσαν και τα δεδομένα ελέγχου (ground truth). Για τα δορυφορικά και υπερφασματικά δεδομένα πραγματοποιήθηκαν οι απαραίτητες ραδιομετρικές και ατμοσφαιρικές διορθώσεις. Τα αποτελέσματα των συσχετίσεων ήταν ενθαρρυντικά τόσο για τα υπερφασματικά δεδομένα όσο και για τα δορυφορικά, και δεν περιορίζονταν μόνο σε παραμέτρους όπως η χλωροφύλλη-α, στην οποία συνήθως επικεντρώνονται οι μελέτες της διεθνούς βιβλιογραφίας, αλλά και σε παραμέτρους όπως το αμμώνιο και το διαλυμένο οξυγόνο. Συγκεκριμένα, στα υπερφασματικά, ο καλύτερος δείκτης για την εκτίμηση της χλωροφύλλης-α ήταν ο ( (R665.7)^(-1) x R 703.5 ) (r2=97.6%), των νιτρικών ιόντων ο λόγος R850.1/R550 (r2=85.7%) και του αμμωνίου ο δείκτης R664.1/550.6 (r2=88.5%). Για την αγωγιμότητα το κανάλι R753.5 έδωσε τα καλύτερα αποτελέσματα (r2=81.7%), για το διαλυμένο οξυγόνο ο λόγος R664/550 (r2=81.9%), για τη θερμοκρασία ο λόγος R670/412 (r2=84%), ενώ για τον ολικό φώσφορο και το pH δεν παρατηρήθηκαν αξιοσημείωτες συσχετίσεις για τους υπό μελέτη δείκτες. Σε αντίστοιχα επίπεδα κινήθηκαν και τα αποτελέσματα για τα δορυφορικά δεδομένα, με τη καλύτερη συσχέτιση χλωροφύλλης-α να εμφανίζεται για το δείκτη R480/(R440+R480+R560) (r2=93.2%), με τα νιτρικά να δίνουν συσχέτιση (r2=82.7%) για το δείκτη exp(R865/R560), το αμμώνιο (r2=87.2%) στο (R440-R655)/(R560-R655), ο ολικός φώσφορος (r2=78.9%) στο (R480-R655)/R560, το pH (r2=79.3%) στο LnR865-LnR1610, την αγωγιμότητα (r2=57.5%) στο R480-R865 και τέλος το διαλυμένο οξυγόνο (r2=90%) για τη διαφορά R560-R655. Όσον αφορά τη θερμοκρασία, τα κανάλια του θερμικού δέκτη έδωσαν ισχυρές συσχετίσεις της τάξης του (r2=95%). Τέλος, και με βάση τα αποτελέσματα αυτά, δημιουργήθηκαν οι αντίστοιχοι χάρτες για την περιοχή μελέτης, τη λίμνη Κάρλα.Nowadays, the need for monitoring and protection of natural environment is greater than ever. Thus, reliable and low cost monitoring methods and techniques are becoming more essential. To this end, cutting-edge technologies from Geo-Informatics and Earth Observation fields form a valuable tool towards effective remote sensing monitoring of aquatic environment. The main objective of this study was to standardize the process of monitoring key water quality parameters in lake ecosystems. Therefore, multiple in-situ, analytical and satellite multispectral data were acquired, processed and fused in the study area Lake Karla, Greece. In particular, Landsat 8 satellite images, hyperspectral data from a field spectrometer, physico-chemical and other monitoring parameters from water samples served as the ground truth data, formed the multi-modal dataset. Radiometric and atmospheric corrections were performed to the satellite and hyperspectral data. The experimental results indicated highly correlations between the remote sensing observations and the in-situ data for key water quality parameters like the concentrations of chlorophyll-a, ammonium and dissolved oxygen. In particular, for the hyperspectral data the highest rates were for chl-a (r2=97.6%), ammonium (r2=88.5%), nitrates (r2=85.7%), conductivity (r2=81.7%) and dissolved oxygen (r2=81.9%). The total phosphorus and the pH didn’t provide stable correlations. For the satellite multispectral data, the highest rates were for chl-a (r2=93.2%), dissolved oxygen (r2=90%), nitrates (r2=82.7%), ammonium (r2=87.2%), total phosphorus (r2=78.9%) and pH (r2=79.3%), while the conductivity (r2=57.5% ) stayed in lower correlation rates. In all cases, the temperature estimation based on Landsat TIRS data established strong relationships at 95% (r2). These preliminary results demonstrate that remote sensing technology and advanced processing techniques can significantly contribute towards the development of a reliable and lowcost off-situ water quality monitoring system for sensitive aquatic ecosystems like the shallow lakes in the greater Mediterranean basin.Ιωάννα Μ. Θεολόγο

User Rofde Identification in Future Mobile Telecommunications Systems

Nevertheless, researchers are working for the specification of the Universal Mobile Telecommunications System (UMTS), which will be a third-generation system for mobile telecommunications. The UMTS [3] will provide a wide range of telecommunication services to a very large number of Mobile Users (MUS). Services highly comparable to those offered by fixed networks will be available via various Mobile Terminals (MTs). The UMTS will be a multi-operator system and will consist of a range of sub-networks, providing userswith access to different environments, according to the entitlement of the subscriptionswith which they are associated. As a user moves between sub-networks during a call, handover functions from one environment to another may take place [4]. Each of these environments has different technical and economic constraints and will require different solutions. In addition, the UMTS radio access point must be able to connect to or cooperate with fixed networks and be capable of operating as a stand-alone network for operation in non-B-ISDN environments, although itsintegrationwithB-ISDNisanobjectivefor UMTS. Other critical aspects of UMTS are the techniques used to store and manipulate the large amount of information involved, and the intelligence needed in order to control calls and cope with user and terminal mobility. In order to make use of a service, a UMTS user will be able to register on an MT for this particular service [5]. Since user registrations will be performed on a per service basis, a user may be registered on more than one MT for different services. Moreover, some types of UMTS terminals will support multiple user registrations,' but only one of the registered users will be allowed to make use of the terminal at a time. The UMTS will also support Universal Personal Telecommunications (UPT), which means that UPT users will be able to register onto (one or more) UMTS terminals in order to make and accept calls. The ability of a user to roam into the various UMTS environments and make use of the resources and services via different terminals will be checked every time this user enters an environment and/or uses resources and services. This means that an information entity must exist for every user so as to be retrieved every time such achecking is required. This user-related information entity is called the UMTS User Profile (UUP). The UUP is stored in the UMTS Distributed Data Base (UMTS DDB) and can be accessed from every point in the network.2 Management operations on a particular user profile can b e performed only by authorized UMTS operators and possibly by the subscriber concemedorbyauser authorizedbythissubscriber. A U U P includes user authentication information, service access information, access domain information, user charging and accounting information, etc. This article discusses the UMTS user profile identification issues. The authors introduce first the concept of user profile and the UMTS entities related to it. Then, the user profile is described and its management requirements are discussed followed by the description of two scenarios proposed for the user profile identification. Finally, the authors give a comparison of the two scenarios and their concluding remarks. The study of the impact of the proposed scenarios upon UMTS operators, subscribers, users, and mobile terminals is beyond the authors' intent for the scope of this article. Entities Related to the UMTS User Profile efore introducing the UMTS User Profile, we B attempt to identify a number of UMTS entities related to this concept

A comparison of multiple Rosetta data sets and 3D model calculations of 67P/Churyumov-Gerasimenko coma around equinox (May 2015)

We have used the latest available shape model for gas and dust simulations of the inner coma of comet 67P/Churyumov-Gerasimenko for the period around May 2015 (equinox). We compare results from a purely insolation-driven model with a complementary set of observations made by ROSINA, VIRTIS, MIRO, and OSIRIS within the same period. The observations include - for the first time - inverted MIRO measurements of gas density, temperature and bulk velocity to constrain the model. The comparisons show that, as in November 2014 (Marschall et al., 2016), insolation-driven activity does not provide an adequate fit to the data. Both VIRTIS and MIRO observations indicate that emissions from the Hatmehit and Imhotep regions of the nucleus are strongly depleted in total gas, H2O, and dust emissions in this case. The MIRO inversion provides a challenging constraint to the models as a consequence of the terminator orbit and nucleus pointing of the spacecraft. Nonetheless a consistent picture with a dominance of outgassing from the Hapi region, even at equinox, is clearly evident. An inhomogeneous model consistent with models proposed for the November 2014 time-frame was constructed and provides a better fit to the data. As far as we are aware this is the first time comae data from four Rosetta instruments have been used to constrain within one self-contained model the emission distribution at the nucleus surface and study the dynamics of the gas and dust outflow

Regional unit definition for the nucleus of comet 67P/Churyumov-Gerasimenko on the SHAP7 model

The previously defined regions on the nucleus of comet 67P/Churyumov-Gerasimenko have been mapped back onto the 3D SHAP7 model of the nucleus (Preusker et al., 2017). The resulting regional definition is therefore self-consistent with boundaries that are well defined in 3 dimensions. The facets belonging to each region are provided as supplementary material. The shape model has then been used to assess inhomogeneity of nucleus surface morphology within individual regions. Several regions show diverse morphology. We propose sub-division of these regions into clearly identifiable units (sub-regions) and a comprehensive table is provided. The surface areas of each sub-region have been computed and statistics based on grouping of unit types are provided. The roughness of each region is also provided in a quantitative manner using a technique derived from computer graphics applications. The quantitative method supports the sub-region definition by showing that differences between sub-regions can be numerically justified

Regional unit definition for the nucleus of comet 67P/Churyumov-Gerasimenko on the SHAP7 model

Open Acces publication. This article is available under the Creative Commons CC-BY-NC-ND license and permits non-commercial use of the work as published, without adaptation or alteration provided the work is fully attributed.The previously defined regions on the nucleus of comet 67P/Churyumov-Gerasimenko have been mapped back onto the 3D SHAP7 model of the nucleus (Preusker et al., 2017). The resulting regional definition is therefore self-consistent with boundaries that are well defined in 3 dimensions. The facets belonging to each region are provided as supplementary material. The shape model has then been used to assess inhomogeneity of nucleus surface morphology within individual regions. Several regions show diverse morphology. We propose sub-division of these regions into clearly identifiable units (sub-regions) and a comprehensive table is provided. The surface areas of each sub-region have been computed and statistics based on grouping of unit types are provided. The roughness of each region is also provided in a quantitative manner using a technique derived from computer graphics applications. The quantitative method supports the sub-region definition by showing that differences between sub-regions can be numerically justified.© 2018 The AuthorsThe team from the University of Bern is supported through the Swiss National Science Foundation and through the NCCR PlanetS. The project has also received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 686709. This work was supported by the Swiss State Secretariat for Education, Research and Innovation (SERI) under contract number 16.0008-2

Quantitative Performance Analysis of Hybrid Mesh Segmentation

This paper presents a comprehensive quantitative performance analysis of hybrid mesh segmentation algorithm. An important contribution of this proposed hybrid mesh segmentation algorithm is that it clusters facets using “facet area” as a novel mesh attribute. The method does not require to set any critical parameters for segmentation. The performance of the proposed algorithm is evaluated by comparing the proposed algorithm with the recently developed state-of-the-art algorithms in terms of coverage, time complexity, and accuracy. The experimentation results on various benchmark test cases demonstrate that Hybrid Mesh Segmentation approach does not depend on complex attributes, and outperforms the existing state-of-the-art algorithms. The simulation reveals that Hybrid Mesh Segmentation achieves a promising performance with coverage of more than 95%

On understanding multi-instrument Rosetta data of the innermost dust and gas coma of comet 67P/Churyumov-Gerasimenko - results, strengths, and limitations of models

Numerical models are powerful tools for understanding the connection between the emitted gas and dust from the surface of comets and the subsequent expansion into space where remote sensing instruments can perform measurements. We will present such a predictive model which can provide synthetic measurements for multiple instruments on board ESA's Rosetta mission to comet 67P/Churyumov-Gerasimenko (hereafter 67P). We will demonstrate why a multi instrument approach is essential and how models can be used to constrain the gas and dust source distribution on the surface

Regional unit definition for the nucleus of comet 67P/Churyumov-Gerasimenko on the SHAP7 model

The previously defined regions on the nucleus of comet 67P/Churyumov-Gerasimenko have been mapped back onto the 3D SHAP7 model of the nucleus (Preusker et al., 2017). The resulting regional definition is therefore self-consistent with boundaries that are well defined in 3 dimensions. The facets belonging to each region are provided as supplementary material. The shape model has then been used to assess inhomogeneity of nucleus surface morphology within individual regions. Several regions show diverse morphology. We propose sub-division of these regions into clearly identifiable units (sub-regions) and a comprehensive table is provided. The surface areas of each sub-region have been computed and statistics based on grouping of unit types are provided. The roughness of each region is also provided in a quantitative manner using a technique derived from computer graphics applications. The quantitative method supports the sub-region definition by showing that differences between sub-regions can be numerically justified