1,223 research outputs found
Automatic segmentation and reconstruction of traffic accident scenarios from mobile laser scanning data
Virtual reconstruction of historic sites, planning of restorations and attachments of new building parts, as well as forest inventory are few examples of fields that benefit from the application of 3D surveying data. Originally using 2D photo based documentation and manual distance measurements, the 3D information obtained from multi camera and laser scanning systems realizes a noticeable improvement regarding the surveying times and the amount of generated 3D information. The 3D data allows a detailed post processing and better visualization of all relevant spatial information. Yet, for the extraction of the required information from the raw scan data and for the generation of useable visual output, time-consuming, complex user-based data processing is still required, using the commercially available 3D software tools.
In this context, the automatic object recognition from 3D point cloud and depth data has been discussed in many different works. The developed tools and methods however, usually only focus on a certain kind of object or the detection of learned invariant surface shapes. Although the resulting methods are applicable for certain practices of data segmentation, they are not necessarily suitable for arbitrary tasks due to the varying requirements of the different fields of research.
This thesis presents a more widespread solution for automatic scene reconstruction from 3D point clouds, targeting street scenarios, specifically for the task of traffic accident scene analysis and documentation. The data, obtained by sampling the scene using a mobile scanning system is evaluated, segmented, and finally used to generate detailed 3D information of the scanned environment.
To realize this aim, this work adapts and validates various existing approaches on laser scan segmentation regarding the application on accident relevant scene information, including road surfaces and markings, vehicles, walls, trees and other salient objects. The approaches are therefore evaluated regarding their suitability and limitations for the given tasks, as well as for possibilities concerning the combined application together with other procedures. The obtained knowledge is used for the development of new algorithms and procedures to allow a satisfying segmentation and reconstruction of the scene, corresponding to the available sampling densities and precisions.
Besides the segmentation of the point cloud data, this thesis presents different visualization and reconstruction methods to achieve a wider range of possible applications of the developed system for data export and utilization in different third party software tools
From surfaces to objects : Recognizing objects using surface information and object models.
This thesis describes research on recognizing partially obscured objects using
surface information like Marr's 2D sketch ([MAR82]) and surface-based geometrical
object models. The goal of the recognition process is to produce a fully
instantiated object hypotheses, with either image evidence for each feature or
explanations for their absence, in terms of self or external occlusion.
The central point of the thesis is that using surface information should be
an important part of the image understanding process. This is because surfaces
are the features that directly link perception to the objects perceived (for
normal "camera-like" sensing) and because surfaces make explicit information
needed to understand and cope with some visual problems (e.g. obscured features).
Further, because surfaces are both the data and model primitive, detailed
recognition can be made both simpler and more complete.
Recognition input is a surface image, which represents surface orientation and
absolute depth. Segmentation criteria are proposed for forming surface patches
with constant curvature character, based on surface shape discontinuities which
become labeled segmentation- boundaries.
Partially obscured object surfaces are reconstructed using stronger surface based
constraints. Surfaces are grouped to form surface clusters, which are 3D
identity-independent solids that often correspond to model primitives. These are
used here as a context within which to select models and find all object features.
True three-dimensional properties of image boundaries, surfaces and surface
clusters are directly estimated using the surface data.
Models are invoked using a network formulation, where individual nodes
represent potential identities for image structures. The links between nodes are
defined by generic and structural relationships. They define indirect evidence relationships
for an identity. Direct evidence for the identities comes from the data
properties. A plausibility computation is defined according to the constraints inherent
in the evidence types. When a node acquires sufficient plausibility, the
model is invoked for the corresponding image structure.Objects are primarily represented using a surface-based geometrical model.
Assemblies are formed from subassemblies and surface primitives, which are
defined using surface shape and boundaries. Variable affixments between assemblies
allow flexibly connected objects.
The initial object reference frame is estimated from model-data surface relationships,
using correspondences suggested by invocation. With the reference
frame, back-facing, tangential, partially self-obscured, totally self-obscured and
fully visible image features are deduced. From these, the oriented model is used
for finding evidence for missing visible model features. IT no evidence is found,
the program attempts to find evidence to justify the features obscured by an unrelated
object. Structured objects are constructed using a hierarchical synthesis
process.
Fully completed hypotheses are verified using both existence and identity
constraints based on surface evidence.
Each of these processes is defined by its computational constraints and are
demonstrated on two test images. These test scenes are interesting because they
contain partially and fully obscured object features, a variety of surface and solid
types and flexibly connected objects. All modeled objects were fully identified
and analyzed to the level represented in their models and were also acceptably
spatially located.
Portions of this work have been reported elsewhere ([FIS83], [FIS85a], [FIS85b],
[FIS86]) by the author
Digital Image Access & Retrieval
The 33th Annual Clinic on Library Applications of Data Processing, held at the University of Illinois at Urbana-Champaign in March of 1996, addressed the theme of "Digital Image Access & Retrieval." The papers from this conference cover a wide range of topics concerning digital imaging technology for visual resource collections. Papers covered three general areas: (1) systems, planning, and implementation; (2) automatic and semi-automatic indexing; and (3) preservation with the bulk of the conference focusing on indexing and retrieval.published or submitted for publicatio
Statistical Assessment of the Significance of Fracture Fits in Trace Evidence
Fracture fits are often regarded as the highest degree of association of trace materials due to the common belief that inherently random fracturing events produce individualizing patterns. Often referred to as physical matches, fracture matches, or physical fits, these assessments consist of the realignment of two or more items with distinctive features and edge morphologies to demonstrate they were once part of the same object. Separated materials may provide a valuable link between items, individuals, or locations in forensic casework in a variety of criminal situations. Physical fit examinations require the use of the examiner’s judgment, which rarely can be supported by a quantifiable uncertainty or vastly reported error rates.
Therefore, there is a need to develop, validate, and standardize fracture fit examination methodology and respective interpretation protocols. This research aimed to develop systematic methods of examination and quantitative measures to assess the significance of trace evidence physical fits. This was facilitated through four main objectives: 1) an in-depth review manuscript consisting of 112 case reports, fractography studies, and quantitative-based studies to provide an organized summary establishing the current physical fit research base, 2) a pilot inter-laboratory study of a systematic, score-based technique previously developed by our research group for evaluation of duct tape physical fit pairs and referred as the Edge Similarity Score (ESS), 3) the initial expansion of ESS methodology into textile materials, and 4) an expanded optimization and evaluation study of X-ray Fluorescence (XRF) Spectroscopy for electrical tape backing analysis, for implementation in an amorphous material of which physical fits may not be feasible due to lack of distinctive features.
Objective 1 was completed through a large-scale literature review and manuscript compilation of 112 fracture fit reports and research studies. Literature was evaluated in three overall categories: case reports, fractography or qualitative-based studies, and quantitative-based studies. In addition, 12 standard operating protocols (SOP) provided by various state and federal-level forensic laboratories were reviewed to provide an assessment of current physical fit practice. A review manuscript was submitted to Forensic Science International and has been accepted for publication. This manuscript provides for the first time, a literature review of physical fits of trace materials and served as the basis for this project.
The pilot inter-laboratory study (Objective 2) consisted of three study kits, each consisting of 7 duct tape comparison pairs with a ground truth of 4 matching pairs (3 of expected M+ qualifier range, 1 of the more difficult M- range) and 3 non-matching pairs (NM). The kits were distributed as a Round Robin study resulting in 16 overall participants and 112 physical fit comparisons. Prior to kit distribution, a consensus on each sample’s ESS was reached between 4 examiners with an agreement criterion of better than ± 10% ESS. Along with the physical comparison pairs, the study iii included a brief, post-study survey allowing the distributors to receive feedback on the participants’ opinions on method ease of use and practicality. No misclassifications were observed across all study kits. The majority (86.6%) of reported ESS scores were within ± 20 ESS compared to consensus values determined before the administration of the test. Accuracy ranged from 88% to 100%, depending on the criteria used for evaluation of the error rates. In addition, on average, 77% of ESS attributed no significant differences from the respective pre-distribution, consensus mean scores when subjected to ANOVA-Dunnett’s analysis using the level of difficulty as blocking variables. These differences were more often observed on sets of higher difficulty (M-, 5 out of 16 participants, or 31%) than on lower difficulty sets (M+ or M-, 3 out of 16 participants, or 19%). Three main observations were derived from the participant results: 1) overall good agreement between ESS reported by examiners was observed, 2) the ESS score represented a good indicator of the quality of the match and rendered low percent of error rates on conclusions 3) those examiners that did not participate in formal method training tended to have ESS falling outside of expected pre-distribution ranges. This interlaboratory study serves as an important precedent, as it represents the largest inter-laboratory study ever reported using a quantitative assessment of physical fits of duct tapes. In addition, the study provides valuable insights to move forward with the standardization of protocols of examination and interpretation.
Objective 3 consisted of a preliminary study on the assessment of 274 total comparisons of stabbed (N=100) and hand-torn (N=174) textile pairs as completed by two examiners. The first 74 comparisons resulted in a high incidence of false exclusions (63%) on textiles prone to distortion, revealing the need to assess suitability prior to physical fit examination of fabrics. For the remaining dataset, five clothing items were subject to fracture of various textile composition and construction. The overall set consisted of 100 comparison pairs, 20 per textile item, 10 each per separation method of stabbed or hand-torn fractured edges, each examined by two analysts. Examiners determined ESS through the analysis of 10 bins of equal divisions of the total fracture edge length. A weighted ESS was also determined with the addition of three optional weighting factors per bin due to the continuation of a pattern, separation characteristics (i.e. damage or protrusions/gaps), or partial pattern fluorescence across the fractured edges. With the addition of a weighted ESS, a rarity ratio was determined as the ratio between the weighted ESS and non-weighted ESS. In addition, the frequency of occurrence of all noted distinctive characteristics leading to the addition of a weighting factor by the examiner was determined. Overall, 93% accuracy was observed for the hand-torn set while 95% accuracy was observed for the stabbed set. Higher misclassification in the hand-torn set was observed in textile items of either 100% polyester composition or jersey knit construction, as higher elasticity led to greater fracture edge distortion. In addition, higher misclassification was observed in the stabbed set for those textiles of no pattern as the stabbed edges led to straight, featureless bins often only associated due to pattern continuation. The results of this study are anticipated to provide valuable knowledge for the future development of protocols for evaluation of relevant features of textile fractures and assessments of the suitability for fracture fit comparisons.
Finally, the XRF methodology optimization and evaluation study (Objective 4) expanded upon our group’s previous discrimination studies by broadening the total sample set of characterized iv tapes and evaluating the use of spectral overlay, spectral contrast angle, and Quadratic Discriminant Analysis (QDA) for the comparison of XRF spectra. The expanded sample set consisted of 114 samples, 94 from different sources, and 20 from the same roll. Twenty sections from the same roll were used to assess intra-roll variability, and for each sample, replicate measurements on different locations of the tape were analyzed (n=3) to assess the intra-sample variability. Inter-source variability was evaluated through 94 rolls of tapes of a variety of labeled brands, manufacturers, and product names. Parameter optimization included a comparison of atmospheric conditions, collection times, and instrumental filters. A study of the effects of adhesive and backing thickness on spectrum collection revealed key implications to the method that required modification to the sample support material Figures of merit assessed included accuracy and discrimination over time, precision, sensitivity, and selectivity. One of the most important contributions of this study is the proposal of alternative objective methods of spectral comparisons. The performance of different methods for comparing and contrasting spectra was evaluated. The optimization of this method was part of an assessment to incorporate XRF to a forensic laboratory protocol for rapid, highly informative elemental analysis of electrical tape backings and to expand examiners’ casework capabilities in the circumstance that a physical fit conclusion is limited due to the amorphous nature of electrical tape backings.
Overall, this work strengthens the fracture fit research base by further developing quantitative methodologies for duct tape and textile materials and initiating widespread distribution of the technique through an inter-laboratory study to begin steps towards laboratory implementation. Additional projects established the current state of forensic physical fit to provide the foundation from which future quantitative work such as the studies presented here must grow and provided highly sensitive techniques of analysis for materials that present limited fracture fit capabilities
Building geometric models with hand-drawn sketches
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Architecture, 1998.Includes bibliographical references (p. 49-51).Architects work on drawings and models, not buildings. Today, in many architectural practices, drawings and models are produced in digital format using Computer-aided Design (CAD) tools. Unquestionably, digital media have changed the way in which many architects perform their day to day activities. But these changes have been limited to the more prosaic aspects of practice. To be sure, CAD systems have made the daily operations of many design offices more efficient; nevertheless, they have been of little use - and indeed are often a hindrance - in situations where the task at hand is more conjectural and speculative in nature, as it is during the early stages of a project. Well-intentioned efforts to insinuate CAD into these aspects of practice have only served to reveal the incongruities between the demands of designer and the configuration of the available tools. One of the chief attributes of design practice is that it is action performed at a distance through the agency of representations. This fundamental trait implies that we have to understand how computers help architects describe buildings if we are to understand how they might help architects design buildings. As obvious as this claim might seem, CAD programs can be almost universally characterized by a tacit denigration of visual representation. In this thesis, I examine properties of design drawings that make them useful to architects. I go on to describe a computer program that I have written that allows a designer to build geometric models using freehand sketches. This program illustrates that it is possible to design a software tool in a way that profits from, rather than negates, the power of visual representations.by Ewan E. Branda.M.S
Computer recognition of occluded curved line drawings
A computer program has been designed to interpret scenes from PEANUTS
cartoons, viewing each scene as a two-dimensional representation of
an event in the three-dimensional world. Characters are identified
by name, their orientation and body position is described, and their
relationship to other objects in the scene is indicated. This
research is seen as an investigation of the problems in recognising
flexible non-geometric objects which are subject to self-occlusion as
well as occlusion by other objects. A hierarchy of models containing both shape and relational
information has been developed to deal with the flexible cartoon
bodies. Although the region is the basic unit used in the analysis,
the hierarchy makes use of intermediate models to group individual
regions into larger more meaningful functional units. These
structures may be shared at a higher level in the hierarchy.
Knowledge of model similarities may be applied to select alternative
models and conserve some results of an incorrect model application.
The various groupings account for differences among the characters or
modifications in appearance due to changes in attitude. Context
information plays a key role in the selection of models to deal with
ambiguous shapes. By emphasising relationships between regions, the
need for a precise description of shape is reduced. Occlusion interferes with the model-based analysis by obscuring the
essential features required by the models. Both the perceived shape
of the regions and the inter-relationships between them are altered.
An heuristic based on the analysis of line junctions is used to
confirm occlusion as the cause of the failure of a model-to-region
match. This heuristic, an extension of the T-joint techniques of
polyhedral domains, deals with "curved" junctions and can be applied
to cases of multi-layered occlusion. The heuristic was found to be
most effective in dealing with occlusion between separate objects;
standard instances of self-occlusion were more effectively handled at
the model level. This thesis describes the development of the program, structuring the
discussion around three main problem areas: models, occlusion, and
the control aspects of the system. Relevant portions of the
programs analyses are used to illustrate each problem area
Rock art in southern Saskatchewan
Prior to the completion of this thesis entitled Rock Art in Southern Saskatchewan very little information regarding rock art in the southern region of the province had been compiled in one place. The purpose of this thesis is to collect information about important rock art sites in southern Saskatchewan and to record the rock art and its current condition. In addition, the rock art of the area is placed in the broader context of Northwestern Plains rock art and interpretations for the rock art found in Saskatchewan are made. Also included is a review of rock art styles found across the Northwestern Plains as defined by Keyser and Klassen (2001), including illustrative examples as well as extensive photographic material and drawings of the sites in southern Saskatchewan. Sites include Crowstand Effigy, St. Victor Petroglyphs, Cabri Lake Petroglyph, Leader Petroglyph, Hazlet Pictographs, Herschel Petroglyphs, Swift Current Petroglyph, Gouldtown and Wood River Petroglyphs, two Last Mountain Lake boulders, Riverhurst Petroglyph, Roche Percee Petroglyphs and Weyburn Petroglyph.
Rock Art in Southern Saskatchewan provides a comprehensive volume on rock art in the region allowing other researchers access to the depth of rock art in the province. It also refines the current knowledge of how and where Saskatchewan rock art fits into the larger picture of artistic activity on the Northwestern Plains
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The earliest instrument : ritual power and fertility magic of the flute in Upper Paleolithic culture
textThe present study examines the earliest known musical instruments, Upper Paleolithic flutes. Flutes dating to the Upper Paleolithic period are the oldest musical instruments that have survived in the archeological record. These have been discovered at archeological sites in Europe dating from approximately 40,000 to 15,000 years ago. Although humans were most likely creating music prior to this time, the people who entered Europe approximately 40,000 years ago began to create musical instruments that have survived to the present day. This study investigates the significance and function of these instruments in Upper Paleolithic culture. Analysis of the artifacts is followed by discussions of archeological contexts, Upper Paleolithic art, ethnographic comparison, and the flute in mythology. Such diverse sources provide multiple layers of evidence regarding the role of the flute in Upper Paleolithic culture. The phallic shape of the instrument and the fact that it is played with the breath, also a symbol of life, connect the flute with the fertility of humans, plants, and animals, the cycle of life and death, and rebirth after death. There is evidence that the flute was intrinsically linked to these themes even in the Upper Paleolithic period, in which the flute was of vital significance, as it was magically imbued with the power to bestow life.Musi
Images out of water : aspects of the interpretation of Ancient maritime grafitti
Pictorial graffiti representing ships from prehistory, protohistory and the early medieval period are frequently examined by nautical historians and archaeologists seeking information about ancient ship technology. Examples of the academic discussion and interpretation of these images may be found from the nineteenth century to the present day, in a wide range of studies. Many of these works reflect their writers' casual, even disdainful attitudes to ancient graffiti. This may be seen in their approach to the information which these images appear to contain, which may concentrate, for example, on the certain aspects of particular subjects without reference to details in their immediate or wider contexts, which may have a bearing on the images' form and meaning. In a similar vein, other writers have interpreted ancient ship graffiti using concepts of art, such as the assumption of realism of depiction, which may be inappropriate to some early visual imagery. This thesis argues that ancient ship graffiti need a more detailed and systematic interpretation as both art and artefact before their contribution to nautical history may be more reliably evaluated. In order to explore the many challenges which these graffiti offer, a multi-disciplinary approach is used, to consider aspects of the relationship between formal art and graffiti, the psychology of image making, symbolism, the philosophy of interpretation, archaeology, and the social meaning of physical context. Following these theoretical discussions, five case studies from a number of different regional and chronological groups have been chosen to provide some examples of many of the issues which were considered. It is hoped that this study demonstrates that an approach to the interpretation of ancient ship graffiti which avoids a narrow concentration on nautical technology may reveal more of their potential as evidence, not only for the form and use of early ships, but also for other aspects of life in the past
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