LEE- Uydu Haberleşme ve Uzaktan Algılama-Yüksek Lisans

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  • Öge
    Earthquake damage detection with satellite imagery and deep learning approaches: A case study of the february 2023, Kahramanmaraş, Turkey earthquake sequence
    (Graduate School, 2023-08-14) Elik, Fatma ; Sertel, Elif ; 705201004 ; Satellite Communication and Remote Sensing
    In recent years, the fusion of deep learning techniques, remote sensing technology, and artificial intelligence (AI) has profoundly transformed the field of disaster management and damage assessment. The increased availability of high-resolution satellite imagery and advanced computer vision techniques now makes it possible to analyze Earth observation data at a large scale and with unparalleled precision. This thesis investigates the application of remote sensing and deep learning techniques to perform post-earthquake damage classification using computer vision and focuses specifically on the earthquakes that occurred on February 6th, with an emphasis on Kahramanmaraş province. The objective of this thesis is to investigate the potential of a variety of deep learning techniques, evaluate their accuracy in recognizing structurally compromised buildings, and utilize satellite imagery in conjunction with diverse open-source spatial data to enhance research on earthquakes. This master's thesis specifically delves into the integration of remote sensing, computer vision, and earth observation methods within the field of geophysics and earthquake studies. Thus, in this study it is aimed to showcase the application of computer vision in the analysis of post-earthquake damage and underscore the importance of rapid intervention in such critical situations. The thesis places significant emphasis on the use of satellite imagery and pixel-based classification for the classification of images in earthquake damage assessment. The UNet, DeepLabV3, and PSPNet architectures are implemented using the ArcGIS Pro API for Python, an innovative and supportive tool for scientific research. The primary data source for the investigation is RGB images from Maxar Technologies. The research examines three cities that were affected by the February 6, 2023, Kahramanmaraş earthquake sequences: Kahramanmaraş, Hatay, and Gaziantep. Damage-assessed data points are received thanks to Yer Çizenler Non-Governmental Organization (NGO), and recently modified building footprints are taken from Humanitarian OpenStreetMap (HOTOSM), and they are all used to analyze the damage. Labeled polygons are generated within a 5-meter distance of the damage points. However, assigning values for further and closer distances has a negative impact on the model accuracy. The training data, exported based on the satellite imagery and damage level assigned data points, provides a balanced dataset for Kahramanmaraş, where the building footprints match the images most effectively. In Hatay, the damage level assigned data distribution is the most balanced, but the building footprints do not align well with the images. Gaziantep presents a good match between the building footprints and images, but the distribution of the damaged data classes is highly imbalanced. Consequently, the decision is made to focus on training the model for Kahramanmaraş province due to the similarity in roof and building types, which has the potential to adapt the approach to other cities in the region as well as the earthquake-affected region under investigation. Image sizes of 256x256 pixels with 128 strides and 4 batches gave us the optimum model results among other options in the DeepLabV3 ResNet50 encoder. In conclusion, this master's thesis demonstrates the potential of combining remote sensing, computer vision, and earth observation techniques for geophysics and earthquake studies. Also, it is aimed to use different data types from open sources and use these different data types to make damage detection after earthquakes. The utilization of the ArcGIS Pro Python API, satellite imagery, pixel based classsification, and labeled training data provides insights into damage assessment after earthquakes, with Kahramanmaraş Province serving as the focal point for model training. The findings contribute to the development of efficient and accurate disaster management strategies and lay the foundation for further research in this field.
  • Öge
    Design and simulation of fractal-based ring antennas for 5G wireless communications
    (Graduate School, 2022-12-02) Altaleb, Abdulazeez Ethar ; Eker, Sebahattin ; 705181001 ; Satellite Communications and Remote Sensing
    After the rolling-out of 5G communication systems the development of smaller and more effective components is still ongoing since it is always important to keep up with the development of the technology, therefore smaller compact and easy-to-fabricate components are the main aim of the scientific community these days. Since the 5G systems are somehow smaller than the old systems' components it arises the fact that the newly- designed components have to have space limitations during the design stages. In this work, by focusing on two of the main 5G bands which are the bands centered on 3.5 GHz and 7GHz three types of antennas were designed and implemented by using CST Microwave studio simulator. The antennas were designed using the fractal concept, characterized by space-filling and self-similarity, so there is no need for extra space when we already have a limited one. The design of the first antenna started by designing a cut-angles rectangular patch antenna that propagates at 3.5 GHz, then by copying and then scaling down the same patch and later subtracting it from the main patch we got a single ring cut-angles rectangular patch antenna that propagates at 3.5 GHz with a reflection coefficient of -19 dB and a gain of 2dBi. The second antenna was created by scaling down the full ring of the first antenna and creating a similar inner ring that propagates at 7 GHz center frequency and has a bandwidth between 6.25-8.1 GHz, this antenna can propagate at two different 5G frequency bands centered at 3.5 GHz and 7 GHz respectively. This antenna has a reflection coefficient S11 of around -20 dB for both bands' resonant frequencies and a gain of 2.29 dBi and 2.51 dBi for the two bands at their center frequency. All these antennas have a microstrip feeding line with a length of 16 mm which is equal to something around λ/4 of the first band's center frequency, all the antennas have an FR-4 substrate thickness of 1 mm and a width of the feeding line of 1.6 mm so that together they provide a 50-ohm impedance at the input port which assure that most of the input port's waves are being propagated. Finally, to increase the gain a 4x1 antenna array was designed to propagate at the same bands, this array has two feeding ports that are designed in an inverted way to improve the matching between the array elements, each port is connected to only two propagating elements by a tree-shaped λ/4 length microstrip has a reflection coefficient of around -45 dBi and -35 dB for both bands at their center frequencies, respectively. This array antenna also has a gain for the 3.5Ghz centered band of 5.64 dBi for port 1 and 5.648 dBi for port 2, and for the 7 GHz band, the gain was equal to 8.39 dBi and 8.4 dBi for port 1 and port 2, respectively.
  • Öge
    Design of a reverberation chamber from a shielded room
    (Graduate School, 2022-01-27) Aba, Rıdvan ; Yapar, Ali ; 705181038 ; Satellite Communication and Remote Sensing
    Electromagnetic Compatibility (EMC) has become more important in the last half-century. The reason for this situation is sensors and similar sensitive electronic circuits, which are increasingly used in electronic systems. As a result of increasing electromagnetic pollution, electromagnetic interference (EMI) to systems has started to have very serious consequences. For this reason, some standards and restrictions have been introduced for almost all electronic products to be produced. These standards and restrictions describe the testing of products for electromagnetic compatibility. One of the test environments used in these tests is the reverberation chambers (RC). RCs are systems based on obtaining a uniform field level in a certain volume by stirring the electromagnetic waves emitted from a source in a closed room with the help of a stirrer. In this thesis, studies on the conversion of a screened room to an RC are included. Within the scope of this study, it was investigated whether the screened room is suitable for conversion to an RC and some preliminary measurements and simulations were made. Afterwards, the stirrer design, which is the most important part of an RC, was started. When the studies in the literature were examined, it was thought that the use of a Z-folded stirrer was appropriate. RC simulations were started with RC simulation with a vertically positioned stirrer, designed using ALTAIR FEKO electromagnetic analysis program. Subsequently, RC simulations with horizontally positioned 4-panel and 5-panel stirrers were performed. Then, an RC simulation with two stirrers was performed. In all these simulations, the position and angle of the antenna were kept constant and changes were made on the stirrer. Since the desired uniform field could not be obtained in this way, it was decided to follow a different plan. In the new simulations, the stirrer position was kept the same and changes were made on the location and angles of the antenna. As a result of the simulations, it was decided to produce the configuration that provides the desired uniform field. After the production and assembly of the stirrer were completed, the verification measurements of the RC were made. The matching of the measurements with the simulations showed the successful completion of the work. Although a difference was observed between the lowest usable frequencies (LUF), this was thought to be due to the simplified modelling of the RC. As a result, an RC that can be used in EMC tests was made for the first in Turkey. In the future, studies will continue to develop the established system.
  • Öge
    Cooperative vehicular communication systems with physical layer security and noma techniques
    (Graduate School, 2021-01-22) Koşu, Semiha ; Ata Durak, Lütfiye ; 705181014 ; Satellite Communication and Remote Sensing
    In recent years, with mobile communication systems development, higher bandwidths and higher data rates are required for individual users. Moreover, in the next-generation wireless communications (5G+), with the emergence of smart cities, many autonomous vehicles and infrastructures are expected to connect. In addition to these numerous connections, it must provide ultra-reliable and low-latency communication (URLLC), which is also necessary for next-generation wireless communications. There are studies examining system performance in vehicle-to-vehicle (V2V) and vehicle-to-everything (V2X) communication systems in the literature. The inter-vehicle environment requires lower antenna heights, cost, and hardware complexities due to the high mobility of vehicles compared to other traditional mobile environments. Also, fading environments in inter-vehicle systems are different from those of stationary users in the literature. Besides, this inter-vehicle fading medium is assumed to be the product of channels in the conventional fading medium and is called the cascade channel model. Therefore, the cascade channel model has an adverse effect on overall system performance. However, some techniques have been studied in the literature which improves V2V system performance. Cooperative communications and receive diversity techniques are considered as a potential solution for inter-vehicle communication systems. When vehicles are not close enough to each other, the signal may be transmitted over relay nodes, increasing the source coverage area enabling cooperative communications. On the other hand, multiple antenna systems are used to combine signals in the receiver to increase the reliability of the system. The diversity technique at the receiver, which reaches the optimum result by maximizing the received signal-to-noise ratio (SNR), is considered to be the maximum ratio combining (MRC) technique that corresponds to the sum of all SNR values received at the destination. Thus, system performance is improved compared to the use of a single antenna, and the coverage area of the source node is increased with the help of a relay. Also, the relay can use different transmission protocols while transmitting the information of the source. In the decode-and-forward (DF) relaying protocol, the transmitted signal is decoded in the relay first, and then an estimated version of symbol is transmitted to the target node. In the amplify-and-forward (AF) relaying protocol, the signal received on the relay is amplified and then transmitted to the destination. Unlike DF relaying protocol, the noise component is also amplified and sent to the destination in this transmission technique as a disadvantage. In this thesis, a comparison of DF and AF relaying protocols are studied, assuming that all nodes are mobile in the system. Also, the channels between all vehicle nodes are designated as cascade Rayleigh fading. It is also assumed that the relay is placed co-linearly and with equal distance between source and destination. Moreover, the relay is equipped with a multi-antenna and applies the MRC technique. Results are provided in terms of bit error probability (BEP) versus SNR values. Accordingly, the increasing number of antennas have improved system performance for both AF and DF relaying protocols. As a result, it is shown that the obtained mathematical expressions are consistent with the Monte-Carlo simulation results. With the tremendous increase in mobile devices in recent years, the continuous broadcast feature of mobile nodes has become a fundamental problem for ensuring security in the system. Therefore, information can become available even to illegitimate listeners. In the open system interconnection (OSI) model, as the physical layer is critical, it is crucial to provide security and transmitting secure information to other layers. Jammer and eavesdropper are the two main types of physical layer attacks studied in the literature. In jamming attacks, the jammer deliberately generates a noise, causing the received signal to be distorted at the destination. However, in eavesdropping attacks, the eavesdropper intercepts the confidential information transmitted to the destination. In all types of attacks, the secrecy capacity of the general system decreases. However, physical layer security (PLS) techniques focusing on increasing system security performance are studied in the literature. For instance, a secret key generation is a PLS technique that increases system security by using the randomness of channels. In this method, the secret key is generated based on the channel state information (CSI) between the legitimate users. Therefore, the data is kept confidential since the illegal user fails to predict the key, even empowering them with high power. In this thesis, the eavesdropper is equipped with multiple antennas for a realistic scenario and applies the MRC technique. Moreover, the eavesdropper receives the broadcasted information from both source and relay in the proposed vehicular communication system. The channel models between all mobile nodes are assumed as the cascade Rayleigh fading channel. The secrecy capacity in this system is calculated by subtracting the eavesdropper's capacity from the destination node's capacity. As an evaluation criterion, the secrecy outage probability (SOP) is calculated first. SOP gives the expression when the secrecy capacity falls below a particular threshold value. Moreover, the probability of positive secrecy capacity (PPSC) means that the instantaneous secrecy capacity is always greater than zero is examined. For system performance, it is observed that when the number of receiver antennas of the eavesdropper increases, SOP increases, and PPSC decreases. Finally, the theoretical analyses of SOP and PPSC are verified by Monte-Carlo simulations. In wireless communication networks, several multiple access methods are drawing attention, such as frequency division multiple access (FDMA), time division multiple access (TDMA), and code division multiple access (CDMA). These orthogonal multiple access (OMA) techniques share the same resource and allow multiple users to work simultaneously in a limited spectrum based on frequency, time, or code. In other words, mobile users can access a limited number of the spectrum simultaneously in these techniques. However, spectrum scarcity is encountered in next-generation wireless networks due to users' need for high data rates and limited resources. At this point, the non-orthogonal multiple access (NOMA) technique could be a promising technology for future wireless networks in terms of providing high spectral efficiency and ensuring fairness between users. The basic concept of NOMA is to allocate different power to users and enable them to work on the same resource block (frequency, time, or code). Besides, NOMA can be classified into two categories, power-domain and code-domain. In power-domain NOMA, the signals of current users are superimposed at the base station (BS) and broadcasted towards the users to decode their signals. The transmitted signal is decoded at the users using the successive interference cancellation (SIC) method, starting from the strong user with better channel quality conditions. Unlike traditional OMA techniques, weak users with poorer channel quality are allocated more transmission power in NOMA, while stronger users with better channel quality are allocated less transmission power. This power allocation can considerably compensate for the trade-off between the quality of service of the system and user fairness. In this thesis, the cooperative power-domain downlink NOMA system is studied. The BS communicates with two vehicles via the relay node and operates in half-duplex (HD) mode. Also, relay transmits the signal of the source to the users by applying the AF relaying protocol. Since both relay and users have high mobility, the channel corresponding to link BS and relay is subjected to Rayleigh fading. In contrast, the channels between relay and users are considered as double Rayleigh fading. Since transmitted signals of each user are superimposed, the SIC method helps to decode these signals. It is assumed that the signal of weak user is correctly decoded on the strong user's channel. In other words, the SIC technique is performed perfectly. Additionally, system performance is evaluated in terms of outage probability and ergodic capacity. In both analyzes, the results are provided using different system parameters (power allocation, distance and transmission power of the BS) for the users. Besides, the overall system performance is also taken into account. Finally, the numerical results are consistent with the Monte-Carlo simulation results.
  • Öge
    Bölgesel ölçekte klorofil-a konsantrasyonunun belirlenmesinde sentınel-3 olcı verilerinin kullanım olanaklarının araştırılması
    (Lisansüstü Eğitim Enstitüsü, 2022-01-17) Demir, Başak ; Kaya, Şinasi ; 705181022 ; Uydu Haberleşmesi Ve Uzaktan Algılama ; Satellite Communication and Remote Sensing
    Türkiye güneyde Akdeniz, kuzeyde Karadeniz, batıda Ege Denizi ile çevrilidir. Ülke sınırları içinde bulunan Marmara Denizi, Karadeniz'i Ege Denizi ve Akdeniz'e bağlar. Birbiriyle bağlantılı olan bu denizlerin izlenmesi doğal çevrenin sağlığı ve canlılar için önemlidir. Uzaktan algılama çalışmalarıyla yapılan araştırmalar sonucu denizlerdeki problemler tespit edilmektedir. Marmara Denizi birçok ekosistemi etkilemesiyle birlikte insan sağlığı içinde önemli bir iç denizdir. Denizin kirliliği doğrudan ya da dolaylı yollarla bütün canlıların hayatına olumsuz yansıyacaktır. Evsel, ticari, endüstriyel, doğal ve tarımsal gibi birçok nedenle deniz kirliliği artmaktadır. Bu durum Marmara Denizi'nde organik ve inorganik kirleticilerin çoğalmasıyla deniz suyuna ve denizde bulunan ekosisteme ciddi zararlar vermektedir. Bununla birlikte Avrupa'nın en büyük ikinci nehri olan Tuna Nehri'nin sanayinin yoğun olduğu ülkelerden, yerleşim yerlerinden ve tarım alanlarından geçerek Karadeniz'e ulaşması ve Karadeniz'de oluşturduğu kirliliğin Marmara Denizi'ne yansımasıda deniz kirliliğinde büyük bir etkendir. Sentinel-3 OLCI deniz ve yeryüzü hakkında bilgi kaydeden bir uydudur. Çevre ve iklimsel gözlem çalışmalarında da kullanılmaktadır. Sentinel-3A ve Sentinel-3B olmak üzere iki özdeş uyduya sahiptir. Tez kapsamında Sentinel-3 OLCI uydu görüntü verileriyle Karadeniz'in batısında ve Marmara Denizi'ndeki klorofil-a konsantrasyonunun neden olduğu kirlilik incelenmiştir. Veriler Yerüstü Su Kalitesi Yönetmeliğinde belirlenen su kalite sınıflarına göre 9 sınıfa ayrılmış ve makine öğrenme algoritması olan destek vektör makinesi (SVM) kullanılarak kontrollü sınıflandırma yapılmıştır. Destek vektör makinesi iki sınıflı doğrusal verilerin veya çok sınıflı doğrusal olmayan verilerin sınıflandırılması için tasarlanmış bir algoritmadır. Farklı mevsimlerde alınan 2020 yılına ait sınıflandırılmış uydu görüntülerine göre klorofil-a konsantrasyonunun ilkbaharda en yüksek sonbaharda en düşük olduğu belirlenmiştir. Bununla ilişkili olarak alg konsantrasyonunun da ilkbahar aylarında artış göstermesi bu durumu desteklemektedir. Ek olarak Tuna Nehri'nin Karadeniz'de yarattığı kirliliğin Marmara Denizi'ne yansımasıyla deniz kirliliğinin arttığı değerlendirilmiştir. Suda yaşayan algler fotosentez yapan canlılardır. Deniz yüzeyinin kirli olması güneş ışınlarını engellediği için bu canlıların fotosentez yapmasına izin vermemektedir. Deniz yüzeyinin kirliliği sonucu ısı dengesi de bozulmaktadır. Bunların sonucunda algler çoğalarak salgı üretir ve müsilaj (deniz salyası) problemine neden olmaktadır. 2021 yılının bahar mevsimine ait Sentinel-3 OLCI (Ocean and Land Colour Instrument) uydu görüntü verileri incelendiğinde 2020 yılının bahar mevsimine kıyasla Marmara Denizi'ndeki klorofil-a oranında artış görülmüştür. Buna bağlı olarak oluşan müsilaj Marmara Denizi'nde büyük bir soruna neden olmuştur. Müsilaj probleminin kontrol altına alınabilmesi için Marmara Denizi ve Batı Karadeniz'in düzenli olarak izlenmesi gerekmektedir. Sentinel-3 OLCI verileriyle yapılan çalışmalar, yıl içinde mevsimlere bağlı klorofil-a konsantrasyonundaki değişimin takip edilmesi için iyi bir seçenek olabilir. Bunun dışında OLCI için geçmiş yıllara ait verileri bulmak her zaman mümkün olmamaktadır. Bu durumda yapılan çalışmaların farklı uydu görüntüleriyle desteklenmesi çalışmaların sürdürülebilirliğinin sağlanması açısından bir gereklilik olacaktır.