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Öğe Analitik hiyerarşi yöntemi ile en uygun okul yer seçim analizi: Elazığ merkez örneği(Halil AKINCI, 2025) Durdağ, Utkan Mustafa; Şen, Mehmet Sait; Usta, ZiyaÜlkemizde meydana gelen depremler Elazığ ilini de ciddi şekilde etkileyerek birçok eğitim kurumunun ağır hasar görmesine ve yıkılmasına yol açmıştır. Bu durum, yeni yapılacak okul alanlarının daha uygun ve güvenli yerlerde inşa edilmesi gerekliliğini bir kez daha gündeme getirmiştir. Bu çalışmada, çalışma alanı için 15 uygun kriter belirlenerek Elazığ İli Merkez İlçesi için en uygun okul alanlarının tespit edilmesi hedeflenmiştir. Çalışmada, ÇKKV (Çok Kriterli Karar Verme)yöntemlerinden Analitik Hiyerarşi Yöntemi (AHY) kullanılarak belirlenen kriterlerin ağırlıkları hesaplanmıştır. Ağırlık değerlerine göre, nüfus(%19), mevcut okullara yakınlık(%16) ve dere yataklarına uzaklık(%13) kriterleri toplam ağırlığın yaklaşık yarısını oluşturarak en etkili faktörler olurken, yüksek basınçlı doğalgaz hattına uzaklık(%1) ve yönlenme(%1) en az etkili kriterler arasında yer almıştır. CBS yardımıyla oluşturulan kriter haritaları kullanılarak ağırlıklı çakıştırma analizi gerçekleştirilmiş ve uygunluk haritaları elde edilmiştir. Bu haritalar aracılığıyla en uygun okul alanları tespit edilmiş, ayrıca mevcut okul alanlarının uygunluk durumları değerlendirilmiştir. Sonuçlara göre, çalışma alanının %95,93’ü uygun olmayan alanlar, %2,02’si az uygun alanlar, %1,99’u uygun alanlar ve %0,05’i çok uygun alanlar olarak sınıflandırılmıştır. Çalışma sonucunda elde edilen veriler, gelecekte okul planlaması ve yer seçiminde yol gösterici olabilecek niteliktedir.Öğe Comparison of tree-based ensemble learning algorithms for landslide susceptibility mapping in Murgul (Artvin), Turkey(Springer Science and Business Media Deutschland GmbH, 2024) Usta, Ziya; Akıncı, Halil; Akın, Alper TungaTurkey’s Artvin province is prone to landslides due to its geological structure, rugged topography, and climatic characteristics with intense rainfall. In this study, landslide susceptibility maps (LSMs) of Murgul district in Artvin province were produced. The study employed tree-based ensemble learning algorithms, namely Random Forest (RF), Light Gradient Boosting Machine (LightGBM), Categorical Boosting (CatBoost), and eXtreme Gradient Boosting (XGBoost). LSM was performed using 13 factors, including altitude, aspect, distance to drainage, distance to faults, distance to roads, land cover, lithology, plan curvature, profile curvature, slope, slope length, topographic position index (TPI), and topographic wetness index (TWI). The study utilized a landslide inventory consisting of 54 landslide polygons. Landslide inventory dataset contained 92,446 pixels with a spatial resolution of 10 m. Consistent with the literature, the majority of landslide pixels (70% – 64,712 pixels) were used for model training, and the remaining portion (30% – 27,734 pixels) was used for model validation. Overall accuracy, precision, recall, F1-score, root mean square error (RMSE), and area under the receiver operating characteristic curve (AUC-ROC) were considered as validation metrics. LightGBM and XGBoost were found to have better performance in all validation metrics compared to other algorithms. Additionally, SHapley Additive exPlanations (SHAP) were utilized to explain and interpret the model outputs. As per the LightGBM algorithm, the most influential factors in the occurrence of landslide in the study area were determined to be altitude, lithology, distance to faults, and aspect, whereas TWI, plan and profile curvature were identified as the least influential factors. Finally, it was concluded that the produced LSMs would provide significant contributions to decision makers in reducing the damages caused by landslides in the study area.Öğe Deep learning aided web-based procedural modelling of LOD2 city models(Springer Science and Business Media Deutschland GmbH, 2023) Usta, Ziya; Akın, Alper Tunga; Cömert, ÇetinIn a large variety of smart city applications, the processes are settled with LOD2 (Level of Details) and the generation of the LOD2 models requires the proper generation of the roof geometries. In general, obtaining roof type information and succeeding generations of the LOD2 models requires expensive aerial surveys and time-consuming construction processes. In this study, a methodology to generate LOD2 building models using only 2D building footprints and aerial imagery is explained to overcome these challenges. The roof type information has been obtained from an aerial image that covers the entire study area using a CNN (Convolutional Neural Network) model. Then, the roof geometries have been constructed procedurally by extending and implementing a well-known Straight Skeleton (SS) algorithm for three main types of roofs: flat, gable and hipped. These constructed roof geometries have been combined with LOD1 block models generated by extruding the 2D footprints according to the height attribute. The overall accuracy of the CNN is 89.9% and the class-wise accuracies are over 84% for all classes. The least recall value is observed for the gable roof class, the enhancement options are discussed in the relevant section. The proposed methodology has been developed as a web-based solution utilizing RESTful web services with modern web technologies. In summary, the main novelty of the study is based on two contributions: using DL for gathering roof-type information without any end-user interference and the extension of the SS algorithm for the construction of roof geometries. The final product of this study is a web-based architecture for the rapid generation of the LOD2 building models.Öğe Elaborating and performing optimization approaches for web-based 3D spatial analysis of 3D city models(Mapping Sciences Institute Australia, 2024) Akın, Alper Tunga; Usta, Ziya; Cömert, ÇetinThree-dimensional (3D) geographic information systems (GIS) are vital for urban planning and architectural design, enabling detailed visualization and analysis of urban landscapes. However, the growing size of 3D city data and the transition to web environments cause performance challenges for real-time applications. This study addresses the need for optimizing 3D spatial analyses for the web using Quadtree data structures and multiprocessing tools. Optimization scenarios based on data size and hardware configurations are evaluated, and the best hosting plans for GIS applications on cloud services are also considered.Öğe An interoperable web-based application for 3d city modelling and analysis(Springer Science and Business Media Deutschland GmbH, 2024) Usta, Ziya; Cömert, Çetin; Akın, Alper TungaThis study presents a web-based application developed for the efficient management of large 3D city models (3DCMs) which are challenging in terms of browsers’ memory limits and network traffic management. The application offers functionalities such as 3D tiling, web-based visualization, 3DCM generation from 2D data, and 3D spatial analysis. It complies with international standards and utilizes open-source software components. The application includes a 3D tiling tool that implements the OGC 3D Tiles Standard, allowing users to partition their 3DCMs into optimized tiles for storage, transmission, and rendering. A web-based procedural modeling tool enables users to generate 3DCMs from 2D building footprint data without the need for complex modeling languages. A 3D spatial analysis component empowers users to perform comprehensive spatial analyses within the web-based environment. Leveraging modern web technologies facilitates precise and efficient spatial computations. To provide standardized visualization, the application features a viewer and client application built using HTML5 and WebGL technologies. This viewer adheres closely to the 3D Tiles Standard, enabling immersive navigation and interaction with 3DCMs. By combining these components, this web-based application handles the management of large 3DCMs, offering enhanced visualization, analysis, and model generation capabilities. It represents a milestone in web-based 3D city model management, prioritizing international standards and open-source principles.Öğe Kentsel alanlarda 3B gölge analizi: Artvin Çoruh Üniversitesi örneği(Halil AKINCI, 2025) Usta, ZiyaKentsel alanlarda binaların oluşturduğu gölge etkisi özellikle güneş paneli kurulumu gibi uygulamalarda, kentsel mikroklima ve enerji verimliliği optimizasyonunda kritik bir role sahiptir. Geleneksel 2B analizlerin yetersizliği nedeniyle 3B gölge analizleri, binaların birbirine gölge oluşturma durumunun daha doğru tahmin edilmesini sağlar. Literatürde genellikle 2.5B modeller kullanılarak gölge analizleri yapılmıştır. Ancak bu modeller dikey yüzeylerin etkisini göz ardı etmektedir. Bu çalışmada 3B modeller kullanarak 3B gölge analizi yapılmıştır. 3B modelleme için prosedürel modelleme yöntemi kullanılmış, kat sayıları baz alınarak binalar LOD1 düzeyinde modellenmiştir. Işın İzleme (Ray-Tracing) algoritmasıyla güneşin günlük ve saatlik konumları dikkate alınarak gölge analizleri yapılmıştır. Artvin Çoruh Üniversitesi Seyitler ve Merkez Yerleşkelerinde binalar arası gölge etkisi düşük bulunmuştur. Ancak yakın mesafedeki yüksek binalar gölgeleme etkisi yaratmaktadır. Çatılardan sonra özellikle güney cephelerinin anlamlı düzeyde güneş ışığı aldığı belirlenmiş olup, bu da dış cephelerin de güneş paneli kurulum potansiyeli olduğunu ortaya koymaktadır. Bu çalışma, 3B gölge analizinin kentsel planlama süreçlerinde önemli bir araç olduğunu göstermektedir. Çalışmada elde edilen diğer önemli bir sonuç, analizlerin sadece çatıları değil dış cepheleri de kapsaması gerektiğidir. Bu sayede bina yüzeylerinden maksimum oranda yararlanılarak sürdürülebilir kentsel gelişim ve doğru yer seçimi sağlanabilir.Öğe Leveraging knowledge graphs and semantic web technologies for validating 3D city models(TAYLOR & FRANCIS LTD, 2025) Akın, Alper Tunga; Usta, Ziya; Stoter, Jantien; Arroyo Ohori, Ken; Cömert, ÇetinThe widespread use of three-dimensional (3D) city data plays a significant role in various applications, such as mixed reality, infrastructure facility management, solar potential analysis, navigation, and so on. Ensuring high spatial and semantic quality in these endeavours is crucial to gathering proper results. Ensuring quality means verifying that the data adheres to relevant standards. Although these relevant standards are openly published, there are issues with the names of interoperability and reusability in academic studies and software development efforts. In this study, these issues are addressed using semantic web technologies. Most 3D city models (3DCMs) are treated as knowledge graphs (KG) with this approach. The main contribution of the study is a web-based interoperable tool for validation of CityGML Level of Detail 2 (LOD2) 3DCMs, which is compatible with relevant standards. Besides, an open-source 3DCM-to-KG converter and an open validation ontology are published as by-products while accomplishing the main goal. By virtue of the KG approach, the 3DCM KG becomes capable of carrying its own validation constraints, which come from the validation ontology. With these efforts, this study provides a practical, interoperable solution to improve the quality and usability of 3DCMs and validation plans, fostering consistency across applications while aligning with established standards in the field.Öğe Monitoring mass movements using Network-RTK measurement technique and producing potential rockfall scenarios in a paleo-landslide area(SCIENDO, 2023) Kadi, Fatih; Akın, Alper Tunga; Usta, ZiyaMass movements resulting from landslides cause significant losses in terms of lives and property. Periodic observations of these movements using geodetic measurement techniques help to prevent these losses. Network-RTK measurement technique produces real-time location with centimeter accuracy, based on phase observations using a network of reference stations. In this study, the paleo-landslide area in the Isiklar location of Trabzon province, Esiroglu district, Turkey, was chosen as the application area. This study aims to measure the application area between 2019 and 2021, using the Network-RTK technique to determine the mass movements. Additionally, there is a rock block in an area with a steep slope. The possible movement of this rock block is a threat to infrastructure facilities, residential areas, agricultural areas, and life safety if the mass movement continues. Within this scope, the potential movement scenarios of the block were produced using RocPro3D software and UAV photogrammetry. Scenarios following an ongoing mass movements in the region triggering another mass movement are discussed. In the light of the results obtained, mass movements in the vertical direction of up to 28 cm were detected in the area where the rock block is located in the last 2 years. The periodic continuation of mass movements in the study area, declared a disaster-prone area, confirms the importance of the rock block in the region. In another phase of the study, possible movement scenarios of the rock block were examined using a rockfall analysis. In this context, with the help of an unmanned aerial vehicle, a digital elevation model and orthophoto map of the region where the rock block is likely to move was produced and a base map to be used in rockfall analysis was obtained. As a result of the rockfall analysis, maps showing the speed, energy, spread, possible impacts, and stopping points were produced. With the examination of these maps, it has been determined that residential areas, agricultural areas, and infrastructure facilities in the study area may be significantly damaged.Öğe Solo demand, rising rents: how young singles shape urban housing costs(Emerald Publishing, 2025) Çalışkan, Bilal; Usta, Ziya; Hatami, MasudPurpose – This study investigates how the concentration of young single-person households (aged 24–35 years) influences small-unit rental prices in Istanbul’s fragmented housing market. Amid rapid demographic shifts and urban restructuring, this paper aims to provide robust causal evidence on the demand-side pressures driven by young singles in shaping rental dynamics, particularly in the increasingly competitive one-bedroom apartment segment. Design/methodology/approach – Using a novel cross-sectional data set covering 605 neighborhoods in Istanbul, this study applies a two-stage least squares instrumental variable strategy to address endogeneity, particularly simultaneity bias. The spatially lagged share of young singles is used as an instrument. The model controls for a rich set of neighborhood-level variables, including accessibility, amenities, income, education, population structure and housing stock age. Findings – A one-percentage-point increase in the share of young single-person households leads to a 4.2% increase in average rents for one-bedroom apartments. These effects are more pronounced in neighborhoods near employment centers, with strong transit access and lifestyle amenities. The results of this study emphasize that demographic clustering at the micro scale drives localized price inflation in the rental market and disproportionately burdens high-demand segments. Originality/value – To the best of the authors’ knowledge, this study is among the first to causally link neighborhood-level solo living patterns to rental inflation in emerging urban contexts. This study advances housing scholarship by segmenting the market by unit size and household structure, while offering policy-relevant insights for managing affordability. The findings of this study support a targeted small-unit housing strategy that responds to evolving demographic realities in dense metropolitan regions.Öğe TKGM CityGML veri modelinin 3B WebCBS uygulamaları açısından irdelenmesi(Halil AKINCI, 2022) Usta, Ziya; Akın, Alper Tunga; Cömert, ÇetinCityGML, kent modellerinin depolanması ve transfer edilmesi için tasarlanmış, açık bir veri modeli ve veri formatıdır. CityGML, 3B CBS uygulamalarında en çok kullanılan veri modeli ve veri formatıdır. TKGM tarafından gerçekleştirilen 3B Kent Modelleri ve 3B Kadastro Projesi kapsamında da CityGML veri modeli ve formatı kullanılmaktadır. Bu proje kapsamında, CityGML veri modeli, veri modelinde tanımlı olmayan 3B kadastro çalışmalarında gerekli verilerin tutulması için genişletilmelidir. Bu bağlamda TKGM, örnek “TKGM CityGML” adlı bir veri modeli tasarlayarak, geliştiriciler için kullanılmak üzere bu veri modeline uygun olarak hazırlanmış örnek bir dosya oluşturmuştur. Bu çalışmada TKGM CityGML veri modeli ve örnek CityGML dosyası incelenmiştir. Böylece TKGM CityGML veri modeline göre gerçekleştirilecek 3B CBS projelerinde veri modeli ve veri formatından dolayı oluşabilecek sorunlar irdelenmiştir. Bu veri modelinin, veri tekrarına sebep olduğu, içerisindeki verilerin ayrıştırılmasının zor olduğu görülmüştür. Özellikle web uygulamaları için TKGM CityGML veri modeli ve formatının uygun olmadığı görülmüş, bu çalışma kapsamında tespit edilen sorunları gideren yeni bir veri modeli ve formatı önerilmiştirÖğe Üç boyutlu konumsal verinin web tabanlı yönetiminde, ogc standardı 3d tiles’ın hiyerarşik veri yapılarıyla gerçekleştirimi(Halil AKINCI, 2022) Usta, Ziya; Cömert, Çetin3B Kent Modelleri (3BKM) pek çok kent objesinden oluşan yüksek veri hacmine sahip verilerdir. Bu durum 3BKM’lerinin web tabanlı olarak yönetilmesi ve görüntülenmesinde performans sorunları yaratmaktadır. Bu nedenle 3BKM’lerinin bölümlenerek (tiling) daha küçük bölümlere ayrılmaları gerekmektedir. 3D Tiles büyük boyutlardaki 3B veri kümelerinin web üzerinden transferi için tasarlanmış bir spesifikasyon ve OGC standardıdır. 3D Tiles’ın temeli, yalnızca görüntüde görünecek olan bölümlerin web üzerinden transfer edilmesini sağlayan hiyerarşik detay seviyelerine dayanmaktadır. 3BKM’lerinin 3D Tiles spesifikasyonuna göre bölümlenmesini sağlayan herhangi bir açık kaynak kodlu (AKK) web tabanlı yazılım bileşeni bulunmamaktadır. Bu çalışmada 3D Tiles spesifikasyonuna uygun olarak 3B bölümleme yapan web tabanlı açık kaynak kodlu (AKK) yazılım bileşeni geliştirilmiştir. Bölümleme için R-Tree ve Adaptive QuadTree hiyerarşik veri yapıları kullanılmıştır. Üretilen 3B bölümler Cesium.js AKK JavaScript kütüphanesi kullanılarak görselleştirilmiştir. Adaptive Quadtree ve R-Tree veri yapıları 3B bölümleme açısından irdelenmiş, oluşturulma süreleri, veri güncelleme süreleri ve konumsal sorgu performansları karşılaştırılmıştır. Böylelikle geliştirilecek uygulamanın genel özelliklerine göre hangi veri yapısının seçilmesi gerektiği belirlenmiştir.Öğe Webgpu: A new graphic api for 3d webgis applications(International Society for Photogrammetry and Remote Sensing, 2024) Usta, ZiyaAs smart city applications increase today, the importance of web-based representations of data that serve as inputs for these applications, such as 3D city models and digital twins, is growing. Since 2011, GPU hardware has greatly advanced, and detailed 3DCMs and digital twins have increased the size of the data to be displayed, which in turn increases performance requirements. WebGL, which couldn’t fully harness the capabilities and power of modern GPUs, began to struggle to meet the increasing performance demands over time and become a bit outdated. Consequently, a new graphic API named WebGPU was developed by W3C as a response to limitations of WebGL and went live with Chrome 113. Now, we have a brand-new graphic API called WebGPU which harness the full power of modern GPUs and more performant than WebGL. As WebGPU is a new graphic API, its potential enhancements and what it can bring over WebGL in the terms of WebGIS have not been examined yet. Hence, the main idea and contribution of this work is to investigate WebGPU in real-world use cases for WebGIS applications and discuss what it brings over WebGL. For this purpose, a side-by-side performance comparison has been made. The comparisons have been made in the terms of API differences and performance. And finally, an experiment has been carried out how much data can be rendered can be rendered at minimum 60fps in both APIs. The experiments show that WebGPU is more low-level and way more performant than WebGL and it has a lot to offer in the terms of WebGIS applications.
