Total least squares registration of 3D surfaces

Co-registration of point clouds of partially scanned objects is the first step of the 3D modeling workflow. The aim of coregistration is to merge the overlapping point clouds by estimating the spatial transformation parameters. In computer vision and photogrammetry domain one of the most popular methods is the ICP (Iterative Closest Point) algorithm and its variants. There exist the 3D Least Squares (LS) matching methods as well (Gruen and Akca, 2005). The co-registration methods commonly use the least squares (LS) estimation method in which the unknown transformation parameters of the (floating) search surface is functionally related to the observation of the (fixed) template surface. Here, the stochastic properties of the search surfaces are usually omitted. This omission is expected to be minor and does not disturb the solution vector significantly. However, the a posteriori covariance matrix will be affected by the neglected uncertainty of the function values of the search surface. . This causes deterioration in the realistic precision estimates. In order to overcome this limitation, we propose a method where the stochastic properties of both the observations and the parameters are considered under an errors-in-variables (EIV) model. The experiments have been carried out using diverse laser scanning data sets and the results of EIV with the ICP and the conventional LS matching methods have been compared.Publisher's Versio

Co-registration of 3d point clouds by using an errors-in-variables model

Co-registration of point clouds of partially scanned objects is the first step of the 3D modeling workflow. The aim of co-registration is to merge the overlapping point clouds by estimating the spatial transformation parameters. In the literature, one of the most popular methods is the ICP (Iterative Closest Point) algorithm and its variants. There exist the 3D least squares (LS) matching methods as well. In most of the co-registration methods, the stochastic properties of the search surfaces are usually omitted. This omission is expected to be minor and does not disturb the solution vector significantly. However, the a posteriori covariance matrix will be affected by the neglected uncertainty of the function values. This causes deterioration in the realistic precision estimates. In order to overcome this limitation, we propose a new method where the stochastic properties of both (template and search) surfaces are considered under an errors-in-variables (EIV) model. The experiments have been carried out using a close range laser scanning data set and the results of the conventional and EIV types of the ICP matching methods have been compared.Publisher's Versio

Photogrammetric deformation monitoring of the second Bosphorus Bridge in Istanbul

Improving the efficiency of bridge inspection and minimizing the impact of dynamic load on the long term deterioration of the bridge structure reduces maintenance and upkeep costs whilst also improving bridge longevity and safety. This paper presents the results of an on-going project whose ultimate goal is the real-time photogrammetric monitoring the structural deformations of the second Bosphorus Bridge of Istanbul.Publisher's Versio

The visualisation with being theory in Location-Based Services

Son yıllarda, Konum Destekli Hizmetler (KDH - Location Based Services), cep telefonları ve avuç içi bilgisayarları gibi mobil cihazların ekran ve işlemci kapasitesinin gelişmesi ile ön planda yer almıştır. Mobil cihaz kullanıcısının talepleri doğrultusunda anlık konum bilgilerinin ölçülmesi, değerlendirilmesi ve sunumu, tüm gelişmelere rağmen özellikle cep telefonlarındaki kısıtlı donanım yapılandırması sebebiyle çözüm gerektiren bir konudur. GPS ve diğer özel algılayıcıların günlük hayatımıza girmesi ile bilgisayarlar tarafından insan davranışlarının belirli düzeyde tespit olanağı sağlanmıştır. Bu da uygun modellemeler ile durum duyarlı uygulamalara imkân vermektedir. İnsan-bilgisayar ilişkisi çerçevesinde bilgisayarların insan dilini anlayamaması birçok konuda sorun yaratmaktaydı. Bu durum bilgisayar bilimlerinde anlamsal (semantik) yaklaşımlar ile aşılmaya çalışılmıştır. Anlamsal bilgisayar dilleri hem insanın hem de makinelerin anlayabileceği bir dil üretmiştir: OWL (Ontology Web Language). Bu dil, varlık felsefesinden doğan “ontoloji” (varlık teorisi) ile, internet dünyasındaki devasal web bilgi yığınını bilgisayarların anlayacağı bir duruma getirmek maksadıyla ortaya konulmuştur. Daha sonrasında tanımsal mantık (description logics) ile desteklenmesi ile durum-duyarlı uygulamalar için neredeyse bir standart halini almıştır. Bu çalışmada çevresel durum duyarlı (context-aware) bir görselleştirme için küme tasarımı ve üretim aşamaları açıklanmaktır. Varlık modelinin oluşturulabilmesi için öncelikle mekânsal veri türlerinin varlıksal tanımları ve birbirleri arasındaki ilişkileri ortaya konmuştur. Çevresel durum duyarlı uygulamaların en önemli gereksinimi tutarlı bir kontext modeldir. Bu modelin tutarlılığı uygulamanın değişik durumlara karşı olan duyarlılık hassasiyetini belirler. Anahtar Kelimeler: Ontoloji, mekansal veri, Konum Destekli Hizmetler (KDH), görselleştirme. Recently, the visualization of spatial data has been gaining importance in ubiquitous computing. In Geoinformatics, such as distributed GIS or Location-Based Services, context models are responsible for the robust communication between the mobile user and the system. "Context" and "context awareness" are the key notions in realisation of the situational information. Context is information characterising the situation of an entity and one of the important entities of the context definition itself is "person". A well-defined context-aware system should fulfil the user's task appropriately. Context-aware systems are a serious consideration in ubiquitous systems and these systems reflect the delicate effect of the designed context. An efficient contextual system needs ontologies. Characteristics of chosen ontology languages determine not only the achievement of the representation of the context but also the capabilities of its reasoning. Ontology Web Language (OWL), an improved version of the DAML+OIL Web Ontology Language, particularly enables description logic support. Description Logics (DLs) allows knowledge representation with concept descriptions and role constructors. OWL-DL is the preferred subset of the OWL to provide reasoning in a well-defined way. To develop a user-adaptive ontological model, users' different situations should be defined properly. In Location-Based Services (LBS), a very intelligent system ignores the effect of user's states and roles except the user's location. Customised visualisation style, however, needs different user profiles in order to provide relevant spatial data. In the computer and cartographic sciences, individual and short-term usage have brought about term of egocentric maps for mobile devices. Design patterns of egocentric maps satisfying user's ego-centre determine visualisation parameters such as centring, redundant encoding, continuous varying of level of details, multiple levels of details, space contraction, single window with details on demand, augmented focusing, orientation gesture and affective emphasis. The aim of this research is to define mobile contextual ontologies (classes and properties) which obey relevance theories so as to define any user's relevant visualisation profile on the mobile devices. The kind of intelligent system proposed here can therefore reason over the complete semantic model of the OWL language by an inference engine. A contextual ontology (OWL-DL) for relevancy has been edited in an ontology editor and knowledge acquisition system. Consequently, the inference engine retrieves criteria for relevant visualisation profiles with its reasoning algorithms or defined SWRL (Semantic Web Rule Language) as a server. In the article, the visual parameter concept has been added to the upper context model to state the visual components of the spatial data as an important part of the system. Data type properties of the visual parameter concept have also been placed on the upper ontology. Subconcepts of the visual parameter have been defined as line and node. The relation between a concept and a subconcept is "is a" relation. Therefore, it can be stated that a line is a visual parameter and a node is a visual parameter. Actually, spatial data can be represented in three main geographic features: point, line and polygon. In the research, the polygon feature has been eliminated while representing spatial data. All polygonal data have been converted to the central point of it because of the limited display size of the mobile devices. Consequently, the visualization has been realized as the line and the node. Egocentric design of a Map-based service which provides relevant visualisation for mobile users is implemented in the campus area of the Istanbul Technical University. Implementation of the service is intended to test consistency of the proposed model for the real user world. A multi-tier technological architecture has been designed that includes spatial database, knowledge base and web map server (WMS). To connect the mobile devices to the servers, a web server and a proxy server have also been set up as in the middleware architecture. GPRS connection, that is the only wireless connection provided by the mobile phone operators, has been used in the research. The UMTS has not been provided yet in Turkey. A GUI that collects information from mobile users has been designed. The architecture has been composed with Java 2EE and Java 2ME programming. To implement the inference procedure the semantic query language (nRQL) has been used. Keywords: Ontology, spatial data, Location-Based Services (LBS), visualisation

An application for industrial close range photogrammetric expert system

Günümüzde, mikrofotogrametri elektronik sanayisinden sağlık hizmetlerine ve özellikle uzay sanayisine kadar pek çok bilimle ortak olarak çalışmaktadır. Bu çalışmalara destek sağlayan ve çalışmalarda kullanılan uzman sistemler laboratuar çalışmalarında önemli bir yer tutmaktadır. Dijital olarak 0.5 cm ve daha küçük objelerin modellenmesi, ölçülmesi ve kalite kontrolünün sağlanması amacına yönelik olan bu sistem aynı zamanda uydu ve uzay çalışmalarında kullanılan dijital sensörlerin testi, kalibrasyonu ve modern görüntüleme ve ölçme çalışmalarında da kullanılabilmekte ve bu sayede üniversitemizde yapılacak birçok lisans, yüksek lisans ve doktora çalışmasında temel sistem olacaktır. Ayrıca ekonomik yönden, yüksek hassasiyette yapılması gereken çalışmalar için üniversitemize destek sağlayacaktır.  Anahtar Kelimeler: Yakın resim fotogrametrisi, uzman sistem, endüstriyel ölçme. Nowadays, microphotogrammetric works have been dealing with the other science like electronic, medicine especially space technology researchers. Expert Systems, which have been used for this works, have been improved and become important day by day. Therefore an expert system would have been built and used for researching the new technologies and measuring the very small objects for quality control and 3D modeling with aided computer vision technologies also using new calibration researching for the sensor technologies, etc. Firstly, built an expert system and calibrate this system is the aim of this Ph.D. Thesis. After that this expert system will have been used for diploma thesis, Master Degree Thesis and also Ph.D. Thesis in the future. The modern universities, which deal with this tecnologies of speace reasearching, have an expert system like this for imaging, measuring and researching the sensor technologies. Multisensory remote sensing requires the simultaneous registration and real-time processing of the time-varying multi-sensor image data. The frame-based programming technique was developed to provide the appropriate multi-sensor data management. Any frame-based processing system supports the automatic data updating since the output of any sensor has been changed. The visual programming of data flows is naturally available through the usage of this approach. Keywords: Close range photogrammetry , expert systems, industrial measurements

Detection of tumours by using CT, MR slices and digital images

Bu çalışmada CT, MR kesitleri ve dijital görüntüler kullanılarak, insan vücudunun 3-boyutlu modellerinin oluşturulması ve bu modellerle tümör gibi oluşumların konumlarının yüksek doğrulukta belirlenmesi sağlanmıştır. Çalışmada, hastanın kafasının CT, MR görüntüleri ve dijital fotoğrafları çekilmiştir. Bu görüntülerle hastanın hem beyninin hem de dış yüzünün 3-boyutlu hacim ve yüzey modelleri oluşturulmuş, oluşturulan modeller kontrol noktaları yardımıyla nesne koordinat sistemine dönüştürülmüştür. Dijital fotoğraflar kullanılarak hastanın yüzünün fotorealistik görüntüsü elde edilmiştir. Daha sonra tümör dokuları belirlenmiş ve tümörün konumu hesaplanmıştır. Bu işlemleri gerçekleştirmek için bir medikal görüntüleme ve fotogrametri yazılımı geliştirilmiştir.Anahtar Kelimeler: 3D tıbbi görüntüleme, texture mapping, hacim kaplama, yüzey kaplama.In this study, it?s provided to reconstruct 3D models of a human body by using CT, MR slices and digital images and thus precisely finding locations of abnormalities such as tumors on these 3D models. Volume and surface rendering techniques have been used to construct 3D models of tissues. In this study, an application has been made to find the location of tumor cited on human brain. During the application some control points have been located on to the face of the patient and then her/his head has been scanned with CT and MR scanners. Digital images of the patient?s head, have also been taken. By using CT and MR images, 3D models of both brain tissues and outer face surface have been constructed. These models have been transformed to object coordinate system by using control points. On the other hand, by using digital photographs of patient?s head, photo-realistic visualization of the 3D face model has been obtained by texture mapping. Finally, tumor has been detected and its location has been obtained. In order to realize above works, medical imaging and photogrammetry software has been developed. This software has been coded with Borland C++ Builder. Furthermore, open source VTK C++ libraries, which supports OpenGL have been used and when required, VTK?s functions have been modified. Keywords: 3D medical imaging, texture mapping, volume rendering, surface rendering

Monitoring and analysis of landuse changes in historical periods for the city of Istanbul by means of aerial photography and satellite imagery

Arazi kullanımının belirlenmesi için günümüze değin farklı teknikler kullanılmış, bu teknikler dahilinde değişik veri tipleri değerlendirilmiştir. Yapılan çalışmalar farklı ölçekte olup farklı amaca hizmet etmektedirler. Bu çalışmada, İstanbul kenti için sadece tek bir döneme ait değil, farklı dönemleri içeren arazi kullanımının tesbit edilmesi amaçlanmıştır. Bu şekilde, dönemler arasındaki değişimler tesbit edilerek bu değişimlerin analizleri yapılabilecektir. Adı geçen dönemlerin belirlenmesinde, verinin varlığı ve bu verinin ulaşılabilir olması dikkate alınmıştır. Bu şekilde 2000, 1987/88, 1968 ve 1940’lı yıllar dikkate alınmıştır. 2000 ve 1987/88 yılları için uydu görüntüleri, 1968 ve 1940’lı yıllar için hava fotoğrafları kullanılması planlanmıştır. Temel topoğrafik veri olarak farklı ölçekte basılı ve sayısal haritalar kullanılmıştır. Çalışmanın doğruluğunun araştırması sadece geometrik olarak yapılmayacak, çalışmanın sonucunda oluşturulacak coğrafi bilgi sistemi için tematik doğruluk araştırması da gerçekleştirilmiştir. Anahtar Kelimeler: Arazi kullanımı, coğrafi bilgi sistemi, konumsal doğruluk, tematik doğruluk.In order to monitor landuse types, several techniques have been used, by which several types of data have been evaluated. These studies are in different scale and have different aims. In this study, it is aimed that to monitor the landuse types for Istanbul not only for one period but also for different periods. This allows making an analysis on landuse changes between these periods. By selecting these periods, existence of data was the defining parameter. So, the years 2000, 1987/88, 1968 and 1940?ies have been taken as evaluation years. It is planned to use satellite imagery for the years 2000 and 1987/88, aerial photographs for the years 1968 and 1940?ies. For the year 2000, IKONOS and IRS-1C/D images and for 1987/88, KVR-1000 and KFA-1000 satellite images are used. As basic topographic data, hardcopy and softcopy maps from different scale are dealt with. In order to define the landuse changes between evaluation years, a unique coordinate system has been used within the whole study. It would be suitable that having this coordinate system the same datum as the conventional maps in order to make an accuracy assessment at the end of the study. This accuracy assessment would not be only about the geometry but also a thematic accuracy investigation would take place for the geographical information system, which was produced at the end of the study.Keywords: Landuse, geographical information system, geometric accuracy, thematic accurac

Yüksek çözünürlüklü uydu görüntülerinin geometrik doğruluk yönünden incelenmesi

The high quality level that high resolution satellite images have reached in the last years has proved that these images could be a useful data source for the production of orthophoto images and different mapping products. Specifically, it is very important in areas where aerial photogrammetry is not possible or feasible due to political reasons / restrictions and mapping frequency constrained by the limits of flight planning. Research activities about high resolution satellite images have been mainly focusing on the geometric accuracy aspects in ortho-image generation and Digital Elevation Model (DEM) extraction. In addition to these activities, some researches are increasingly concentrating on feature detection, recognition and reconstruction studies like automated mapping of roads, extraction of 3D buildings and cadastral mapping. There are two important criteria for quality assessment of the images; geometric accuracy and object definition. When we take the mapping processes into consideration, these criteria are basically dependent on the relation between pixel size and the map scale, contrast information (spectral range and colour), atmosphere and the sun elevation, the printing technology and the resolution of the human eye in a usual reading distance. A study has been implemented in Gölbaşı near Ankara, which has 10 km X 10 km area and a height difference about 440 m, for geometric accuracy assessment of high resolution satellite images. 12 ground control points were revised and signalized before the recording of images. Stereo-pair Ikonos (dated August 4th, 2002) and mono Quickbird (dated May 26th, 2002) images and 1/16000 scaled aerial photographs (dated August 29th, 2002) have been provided by Inta (Turkey), Eurimage (Italy) and General Command of Mapping (Turkey) free of charge. For geometric accuracy assessment; different digital elevation models (DEM’s) have been created using photogrammetric and cartographic methods. Photogrammetric DEM has been produced using 1/16000 scaled stereo aerial photographs and has accuracy about 1 m. From the other side, cartographic DEM has been produced digitizing map contours and has accuracy about 5 m. And lastly, Ikonos DEM has been produced from stereo-pair Ikonos images automatically and has accuracy about 2 m. With these models, various orthophoto and mosaic images have been produced using ground control points. Used ground control points have had different distributions and number of points between 0 and 11. Well-recognized 27 checkpoints such as road junctions and field corners have been selected and measured with GPS. Planimetric coordinates of the checkpoints were measured on all orthophoto, mosaic and stereo images. These coordinates have been compared with GPS coordinates. From the comparison of these measurements, the differences and also the errors have been obtained. Afterwards the gross error positions have been evaluated according to ground control points’ network. The geometric accuracy results show that IKONOS - DEM can be used instead of photogrammetric DEM, the quality of GCP’s is as important as the number of GCP’s, systematic errors have occured in the easting / north easting (across track) direction and IKONOS images have better accuracy than Quickbird images when using direct sensor orientation parameters. Also we can say that the high resolution satellite images can be used in mid / large also from 1/6000 to 1/10000 scale map productions and these results are harmonious with the examples given in the literature. Actually there is nearly a consensus among photogrammetry and remote sensing society that some mapping applications from high resolution space imagery can be realized in mid / large scale. In addition, in spite of increasingly concentrating by some researches on feature detection, recognition and reconstruction studies in high resolution satellite images, it can not be said that these images couldn’t reach to the level of aerial images in determining and identifying of small features in big scale maps (e.g. 1/5000) yet. Therefore the discussions about usage of high resolution space imagery in big scaled map production are still lasting.  Keywords: High resolution, satellite images, orthophoto, control point, Digital Elevation Model (DEM).Yüksek çözünürlüklü uydu görüntülerinin son yıllarda eriştiği üstün kalite düzeyi, bu verilerin ortofoto görüntüler ve farklı haritacılık üretimleri konusunda iyi bir veri kaynağı olabileceğini kanıtlamıştır. Ancak günümüzde halen, yüksek çözünürlüklü uydu görüntülerinin büyük ölçekli harita üretim çalışmalarında kullanılabilmesine ilişkin tartışmalar sürmektedir. Bu nedenle, yüksek çözünürlüklü uydu görüntülerinin geometrik doğruluk yönünden incelenmesi amacıyla, 10 km x 10 km boyutlarında bir alana ve 440 m yükseklik farkına sahip olan Ankara yakınlarındaki Gölbaşı bölgesinde bir çalışma gerçekleştirilmiştir. Bu çalışma için 12 adet Yer Kontrol Noktası (YKN) tespit edilmiş ve görüntü alımından önce bu noktalar işaretlenmiştir. Daha sonra stereo Ikonos (4 Ağustos 2002 tarihli) ve mono Quickbird görüntüleri ile 1/16000 ölçekli stereo hava fotoğrafları (29 Ağustos 2002 tarihli)  temin edilmiştir. Geometrik doğruluk çalışması için öncelikle fotogrametrik ve kartografik yöntemler ile Ikonos uydu görüntülerinden Sayısal Yükseklik Modelleri (SYM) elde edilmiş ve farklı sayı ve dağılımda bulunan YKN kullanılarak değişik özelliklere sahip ortofotolar üretilmiştir. Arazide belirgin olarak tespit edilebilen 27 adet bağımsız kontrol noktası (test noktası) seçilmiş ve bunların koordinatları GPS ile arazide ölçülmüştür. Bağımsız kontrol noktalarının GPS koordinatları, aynı noktaların tüm ortofoto görüntüler üzerinde okunan koordinatları ile karşılaştırılmış ve aradaki farklar belirlenmiştir. Geometrik doğruluk araştırmaları sonucunda yapılan değerlendirmeler, yüksek çözünürlüklü uydu görüntülerinin orta/büyük ölçekli (1/6000–1/10000) harita üretim çalışmalarında kullanılabileceğini göstermektedir. Anahtar Kelimeler: Yüksek çözünürlük, ortofoto, kontrol noktası, Sayısal Yükseklik Modeli (SYM)

Determining pull - out deformations of bonded metal anchors embedded in concrete by means of photogrammetry

Chemical anchorages are applied in many engineering implementations, particularly strengthening of reinforced concrete structures. During strengthening procedure; chemical anchorages should be tested, since they supply to transfer the load between existing construction elements and newly added elements. Therefore; the study of the quality of chemical anchorages is an important issue in construction materials science. In this context; the most important experiment is to determine the pull-out loads of embedded anchorage reinforcement by applying axial loads. In this study; it is aimed to determine the displacements of steel reinforcements, embedded into concrete by using chemical anchorages, while applying axial pulling loads. In order to determine the displacements and load - deformation graphs; starting conditions and every 10 bar pressure applied conditions of the steel reinforcements were captured by the cameras. The obtained images were evaluated by using photogrammetric software. Based on the photogrammetric post-processing results, the load - deformation graphs were plotted and the loads at loss of adhesion were determined.Publisher's Versio