Showing papers by "Sultan Kocaman published in 2018"

Semi-Automatic 3D City Model Generation from Large-Format Aerial Images

Abstract: 3D city models have become crucial for better city management, and can be used for various purposes such as disaster management, navigation, solar potential computation and planning simulations. 3D city models are not only visual models, and they can also be used for thematic queries and analyzes with the help of semantic data. The models can be produced using different data sources and methods. In this study, vector basemaps and large-format aerial images, which are regularly produced in accordance with the large scale map production regulations in Turkey, have been used to develop a workflow for semi-automatic 3D city model generation. The aim of this study is to propose a procedure for the production of 3D city models from existing aerial photogrammetric datasets without additional data acquisition efforts and/or costly manual editing. To prove the methodology, a 3D city model has been generated with semi-automatic methods at LoD2 (Level of Detail 2) of CityGML (City Geographic Markup Language) using the data of the study area over Cesme Town of Izmir Province, Turkey. The generated model is automatically textured and additional developments have been performed for 3D visualization of the model on the web. The problems encountered throughout the study and approaches to solve them are presented here. Consequently, the approach introduced in this study yields promising results for low-cost 3D city model production with the data at hand.

Considerations on the use of sentinel-1 data in flood mapping in urban areas: ankara (turkey) 2018 floods

Abstract: . Flood events frequently occur due to -most probably- climate change on our planet in the recent years. Rapid urbanization also causes imperfections in city planning, such as insufficient considerations of the environmental factors and the lack of proper infrastructure development. Mapping of inundation level following a flood event is thus important in evaluation of flood models and flood hazard and risk analyzes. This task can be harder in urban areas, where the effect of the disaster can be more severe and even cause loss of lives. With the increased temporal and spatial availability of SAR (Synthetic Aperture Radar) data, several flood detection applications appear in the literature although their use in urban areas so far relatively limited. In this study, one flood event occurred in Ankara, Turkey, in May 2018 has been mapped using Sentinel-1 SAR data. The preprocessing of Sentinel-1 data and the mapping procedure have been described in detail and the results have been evaluated and discussed accordingly. The results of this study show that SAR sensors provide fast and accurate data during the flooding using appropriate methods, and due to the nature of the flood events, i.e. heavy cloud coverage, it is currently irreplaceable by optical remote sensing techniques.

A review on citizen science (citsci) applications for disaster management

Abstract: . The traditional way of doing science has been changing with the recent movements on open science, open data and the world-wide spread of volunteer activities. With the help of technological advancements, in particular mobile technologies, do-it-yourself kits and free online education sources, ordinary citizens may contribute to scientific processes based on their interest and abilities. Citizen Science (CitSci) is an active research agenda which draws the interest of scientists from different disciplines. It investigates the various contributions that citizens could do to improve scientific process. These contributions are utilized in diverse areas ranging from biology to environmental monitoring to classification of galaxies, all of which have a spatiotemporal dimension. The emerging developments in spatial information science allow the public to understand their environment better and efficiently. In this way society would have the means to deal with complex modern problems including but not limited to water/air pollution monitoring and mapping a region after a natural disaster to aid relief and recovery efforts. In addition, there is a growing public demand for research projects involving CitSci; because such collaborative efforts can be critical to achieve sustainability goals. The aim of this paper is to provide an overview on the state-of-the art methods and applications where CitSci is a crucial component in different phases of disaster management, from environmental protection to risk analysis and aid provision. Use of CitSci methods in disaster situations can be vital for different reasons, such as acquisition of local and most current information, organization of help during emergency, development of instant rescue plans, accurate information dissemination, and monitoring of the post-disaster influences to the society and the environment. Open issues on the use of CitSci methods in disaster management, such as data quality, technical and management-related barriers, open-standards and interoperability, and volunteer engagement, will also be discussed.

Possible contributions of citizen science for landslide hazard assessment

Abstract: . Landslide is perhaps one of the most complex natural phenomena and is quite common throughout the World. Before the human appearance on the World, it was only an earth surface process, whereas it became one of the most destructive natural hazards with the anthropogenic activities and the increase in human population. Landslides cause serious harmful and destructive effects on roads, railways, buildings, infrastructures, lifelines, quality of surface waters, etc. To reduce the losses caused by landslides, high quality landslide susceptibility and hazard maps are crucial. With the recent technological developments, the quality of regional landslide susceptibility and hazard assessments has been increased. Preparation of a complete landslide inventory map with accurate temporal dimension can be extremely difficult, or even impossible. Inaccurate and incomplete temporal landslide inventory maps result in serious uncertainties on the assessment results of regional landslide hazard. Therefore, lack of timely accurate data is the main source of problem affecting quality of the regional landslide assessments. With the emerging developments in geospatial technologies, as well as the transforming power of information and communication technologies (ICT) on the society, it became possible to use the citizen science methods in scientific processes, which has enormous potential in landslide data collection and thus reduce the losses. The main aim of this review is to discuss the uncertainties lead by missing data and affecting quality of regional landslide assessments, and to describe the potential of citizen science to reduce the uncertainties. For this purpose, a brief review on the landslide susceptibility and hazard studies have been performed and the sources of uncertainties have been described. Finally, the role of citizen science is discussed with specific examples. As a final conclusion drawn from the present study, it is possible to say that citizen science may provide substantial contribution on the quality of regional landslide assessments.

Preliminary investigations on flood susceptibility mapping in ankara (turkey) using modified analytical hierarchy process (m-ahp)

Abstract: . Susceptibility mapping for disasters is very important and provides the necessary means for efficient urban planning, such as site selection and the determination of the regulations, risk assessment and the planning of the post-disaster stage, such as emergency plans and activities. The main purpose of the present study is to introduce the preliminary results of an expert based flood susceptibility mapping approach applied in urban areas in case of Ankara, Turkey. The proposed approach is based on Modified Analytic Hierarchy Process (M-AHP), which is an expert-based algorithm and provides data based modeling. The existing spatial datasets are evaluated in the decision process and the specified number of decision points according to the degree desired can be formed. The parameter priorities can be identified at the beginning of the modeling with this approach by the responsible expert. The spatial datasets used in the modeling and mapping process have been provided by the General Directorate of Mapping (HGM). Additionally, the slope gradient of topography, drainage density, and topographic wetness index of the site being one of the second derivatives of topography have been evaluated to identify the main conditioning factors controlling water accumulation on ground. Considering the uncertainties in flood hazard assessment and limitations in sophisticated analytic solutions, the proposed methodology could be evaluated to be an efficient tool to detect the most influential parameters representing the flood vulnerability and assessing the mitigation applications in urban environment.

A 3d campus application based on city models and webgl

Abstract: . In parallel with the technological developments, the conventional ways of mapping and the presentation of the geospatial data have changed significantly. 3D city models including the digital terrain models (DTMs) have become important for many application fields, such as simulation and visualization tasks for navigation, urban planning, environmental monitoring, disaster management, etc. Although currently most 3D city models are employed for visualization purposes, their application areas are increasing continuously. The presentation of these models on the web is also becoming more common than before while overcoming the performance issues with newer data types and functionalities. The biggest advantage of using web browsers is that they can be accessed everywhere without any additional software requirements. Therefore, the tools for web-based implementations of virtual globes, which allow users to navigate their data in 3D, have been available with greater numbers of functionality they offer. Online virtual web globes provide a good base for the 3D Geographical Information System (GIS) applications as well. 3D city models have also become virtual environments where different spatial queries and analysis can be performed. As a part of a 3D WebGIS, a city model enriched with semantic information provides a virtual platform for decision makers and allows realistic simulations for planning. The main aims of this study are to develop a prototype of a 3D GIS environment for Hacettepe University Beytepe campus, including 3D building geometries enriched with semantic information and a high resolution DTM; and to design a web interface using an open source virtual globe.

On the use of citsci and vgi in natural hazard assessment

Abstract: . The developments in the geospatially-enabled mobile communication technologies have opened new horizons in many fields of geosciences research, especially in those where data collection, processing and interpretation are time consuming and costly. Being one of these research fields, natural hazards also require high spatiotemporal data density and distribution, which is extremely difficult to obtain and also equally essential to secure the main assumptions of these researches and thus yield to proper conclusions. These problems can be solved with the help of citizen science (CitSci) methods and the volunteer geographical information (VGI). These two terms are complementary, or intertwined, and mutually benefit from each other for achieving their goals. This paper investigates the developments in CitSci and VGI with a specific focus of natural hazard researches and gives a brief overview of the literature. The importance of their use in natural hazards, open research areas and future aspects are also analysed. Based on the previous experiences and analyses, the authors foresee that such investigations would help researchers to utilize CitSci and VGI in their studies, and thus benefit the advantages of both approaches and improve the quality of their data. On the other hand, the growing interest of citizen scientists for supporting scientific processes could be steered to the fields where most help is needed. Specifically, detection of ground deformations after earthquakes is explained here and a simple mobile app developed for landslide data collection is briefly depicted as use case.

CitSci as a New Approach for Landslide Researches

Abstract: Landslide is a commonly and frequently observed disaster on the Earth both spatially and temporally. The landslide researches mainly aim at characterizing and understanding this process and the earth dynamics, and predicting their occurrence based on triggering factors, their spatial and temporal dimension, thus assess the hazard potential; and estimating the risks which they cause on the economy, environment, and lives. Due to the great variety and amount of data included in this field, it is crucial to form complete landslide databases both at regional level and worldwide. The main aim of this assessment is to bring new insights to the landslide data acquisition aspect by different users. The need of accurate and reliable geodata collection by ordinary people is inevitable for ensuring sufficient spatiotemporal density and distribution, thus forming extensive landslide databases and simulating and planning the future. With the developments in geoinformation technologies, as well as the transforming power of information and communication technologies (ICT) on the society, it became possible to use the citizen science (CitSci) methods in many scientific fields. It has as well enormous potential in landslide data collection, validation and interpretation, and thus contribute to landslide researches. In this review, the uncertainties lead by missing data and affecting quality of regional landslide assessments are discussed, and the potential of citizen science in landslide researches is described. The role of volunteer data is portrayed with specific examples from the literature. The levels of citizen contribution are depicted accordingly.

Design and developement of trendyinsight application software for location based social media trending

Abstract: . With as many as one third of population have become social media users exchanging information, thanks to low cost smart phones availability and social messaging platforms like Facebook, Twitter, WhatsApp, Instagram etc., TrendyInsight will play a major role on listening the public concern on local or regional issues bothering them for the government authorities to learn and prepare the remedial action. Similarly, businesses of consumer industries will be benefited from TrendyInsight for better customer services. TrendyInsight – an application software designed and developed to work in iOS platform to capture trending topics from various social networks websites based on user location and present it in graphically on map. The application utilizes the uniqueness of each social network data through Application Program Interface (API) requests based on the trend. The application eliminates the need of user login to access the public data of these social networks. The application provides other experience enhancement features like showing user’s current location, updating the trending data every interval of time, searching for custom location, getting data for any custom hashtag, and settings tab to customize the type of data to be received from the social network APIs. The application was built on Swift 4 and deployment target operating system is iOS 11.

Açık Kaynaklı Web Tabanlı Coğrafi Bilgi Sistemi Geliştirilmesi

Abstract: Cografi Bilgi Sistemlerinin (CBS) kullanim alanlari giderek artmakta ve farkli meslek disiplinleri, kullanici gruplari (kisisel, kurumsal, vb.) tarafindan da yogun bir sekilde kullanilmaktadir. Mobil teknolojilerin de gelisimiyle pek cok uygulama, konum verisi kullanir ve toplar hale gelmistir. Internet erisimi CBS ile birlestirilerek toplanan verilerin, dahili bir sistem icerisindeki bilgisayarlarda kalmasi yerine, Internet araciligiyla istenilen kadar verinin kullanicilara aktarilmasi ve paylasimi saglanabilmektedir. Yuksek lisans tezi kapsaminda yapilan bu calismanin amaci; Hacettepe Universitesi bunyesinde, acik kaynak kodlu yazilimlar kullanilarak bir CBS ortami gelistirmektir. Tez kapsaminda acik kaynak kodlu yazilimlar incelenmis, ornek bir sistem tasarlanmis ve secilen yazilimlar uyarlanarak bir Web tabanli CBS uygulamasi gelistirilmistir. Test verileri toplamak ve ayni zamanda bir sivil bilim (gonullu veri toplama) uygulamasi olusturmak amaciyla mobil bir uygulama gelistirilerek kullanicilarindan hissettigi deprem sarsintilarinin derecelendirilmesi, ayni zamanda acik kaynak kodlu bir veri tabaninda toplanarak, Internet uzerinden bir harita sunucusu ile paylasilmasi hedeflenmistir. Kullanicilar “Sarsintiyi Hissettim” isimli Android uygulamasi ile hissettikleri sarsinti derecesini ve ayrica konum bilgilerini veri tabanina gonderebilmektedirler. Acik kaynak kodlu PostgreSQL/PostGIS veritabani ve MapServer harita sunucusu kullanilarak toplanan verinin Internet ortamina sunulmasi saglanmistir. Sunulan verinin icerisinde sarsinti dereceleri, kullanici konum bilgisi, verinin kullanicidan geldigi tarih ve saat, kullanicinin dilerse girmesi icin de ise isim ve soy isim bilgileri yer almaktadir. Bu sistem, universite bunyesinde yapilacak cografi uygulamalara teknolojik altyapi saglayacak, farkli arastirma projeleri ve disiplinler icin bir veri paylasim platformu olarak kullanilabilecek ve bilimsel yontemlerle uretilen bilginin paylasimini ve yayginlastirilmasini kolaylastiracaktir.

Investigations on the radiometric, geometric, and DSM generation qualities of Gokturk-2 stereo images

Abstract: Gokturk-2 is the third Earth observation (EO) satellite of Turkey and acquires high-resolution panchromatic (2.5 m) and multispectral images (5 m) from its near-polar orbit at a nominal altitude of 685 km from the Earth. The push broom scanner mounted on the satellite can obtain both mono and stereo images. Images of Gokturk-2 can be used in many application fields both for defense and civilian use, such as environment and city planning, geology, agriculture, and forestry. The purpose of this study is to evaluate the radiometric and geometric quality of Gokturk-2 stereo images acquired from panchromatic band and the digital surface model (DSM) generation capability from these images. The Gokturk-2 stereo images used in this study have been acquired over a test area located near Kesan town of Edirne Province in Turkey in May 2017. Initially, the radiometric quality has been investigated by statistical analysis of the histogram, noise estimation on homogeneous surfaces, and visual checks. The image orientation has been performed by polynomial modeling of the image trajectories using a number of ground control points (GCPs) extracted from road intersections in cadastral maps. The image orientation accuracy obtained using the GCPs is around 5.4 pixels in planimetry and 4.5 pixels in height for this stereopair. The DSM has been generated with dense feature point matching using normalized cross-correlation. The quality of the generated DSM has been assessed by comparison with a reference digital terrain model (DTM) data in open terrain areas. The results show that despite the inferior image orientation accuracy and radiometric problems, DSMs can be generated with sufficient accuracy especially in open terrain. Major problems occur in forests and also in areas with rugged topography.

A Photogrammetric Surface Comparison for a Dam Reservoir in a Landslide—Prone Area in Eastern Anatolia, Turkey

Abstract: The purpose of the study was to analyze the slope deformations of a dam reservoir by comparing digital elevation models (DEMs) produced before and after data sets. The DEMs were generated automatically from large format aerial images acquired in 2012 and Gokturk-2 satellite images acquired in 2018. Both DEMs were compared and analyzed to obtain slope deformations. The results showed that the reservoir waters affected the slopes and some displacements were seen clearly in northeast slopes of the reservoir. The slope deformations can be monitored accurately with the proposed approach, with a note on the ground resolution of the images, which affected the accuracy and the density of the DEMs directly. The methodology provided promising results for automatic, low-cost and practical monitoring for slope deformations in large mountainous regions.