Sub-canopy terrain modelling for archaeological prospecting in forested areas through multiple-echo discrete-pulse laser ranging: a case study from Chopwell Wood, Tyne & Wear

Airborne Light Detection and Ranging (LiDAR) technology is assessed for its effectiveness as a tool for measuring terrain under forest canopy. To evaluate the capability of multiple-return discrete-pulse airborne laser ranging for detecting and resolving sub-canopy archaeological features, LiDAR data were collected from a helicopter over a forest near Gateshead in July 2009. Coal mining and timber felling have characterised Chopwell Wood, a mixed coniferous and deciduous woodland of 360 hectares, since the Industrial Revolution. The state-of-the-art Optech ALTM 3100EA LiDAR system operated at 70,000 pulses per second and raw data were acquired over the study area at a point density of over 30 points per square metre. Reference terrain elevation data were acquired on-site to ‘train’ the progressive densification filtering algorithm of Axelsson (1999; 2000) to identify laser reflections from the terrain surface. A number of sites, offering a variety of tree species, variable terrain roughness & gradient and understorey vegetation cover of varying density, were identified in the wood to assess the accuracy of filtered LiDAR terrain data. Results showed that the laser scanner over-estimated the elevation of reference terrain data by 13±17 cm under deciduous canopy and 23±18 cm under coniferous canopy. Terrain point density was calculated as 4.1 and 2.4 points per square metre under deciduous and coniferous forest, respectively. Classified terrain points were modelled with the kriging interpolation technique and topographic archaeological features, such as coal tubways (transportation routes) and areas of subsidence over relic mine shafts, were identified in digital terrain models (DTMs) using advanced exaggeration and artificial illumination techniques. Airborne LiDAR is capable of recording high quality terrain data even under the most dense forest canopy, but the accuracy and density of terrain data are controlled by a combination of tree species, forest management practices and understorey vegetation

Digital photogrammetry for visualisation in architecture and archaeology

Bibliography: leaves 117-125.The task of recording our physical heritage is of significant importance: our past cannot be divorced from the present and it plays an integral part in the shaping of our future. This applies not only to structures that are hundreds of years old, but relatively more recent architectural structures also require adequate documentation if they are to be preserved for future generations. In recording such structures, the traditional 2D methods are proving inadequate. It will be beneficial to conservationists, archaeologists, researchers, historians and students alike if accurate and extensive digital 3D models of archaeological structures can be generated. This thesis investigates a method of creating such models, using digital photogrammetry. Three different types of model were generated: 1. the simple CAD (Computer Aided Design) model; 2. an amalgamation of 3D line drawings; and 3. an accurate surface model of the building using DSMs (Digital Surface Models) and orthophotos

Intelligent Data Storage and Retrieval for Design Optimisation – an Overview

This paper documents the findings of a literature review conducted by the Sir Lawrence Wackett Centre for Aerospace Design Technology at RMIT University. The review investigates aspects of a proposed system for intelligent design optimisation. Such a system would be capable of efficiently storing (and compressing if required) a range of types of design data into an intelligent database. This database would be accessed by the system during subsequent design processes, allowing for search of relevant design data for re-use in later designs, allowing it to become very efficient in reducing the time for later designs as the database grows in size. Extensive research has been performed, in both theoretical aspects of the project, and practical examples of current similar systems. This research covers the areas of database systems, database queries, representation and compression of design data, geometric representation and heuristic methods for design applications.

Visualisierung zweidimensionaler Volumen

In dieser Arbeit wird ein neues Verfahren zur Visualisierung zweidimensionaler Volumen vorgestellt. Der Begriff multidimensionales Volumen wird dabei definiert als eine Menge von räumlich dreidimensionalen Datensätzen, die jeder eine andere Eigenschaft (eine physikalische Qualität, z.B. Dichte oder Temperatur) desselben Objekts beschreiben. Zweidimensionale Volumen beschreiben also zwei verschiedene Eigenschaften eines Objekts. Sie entstehen z.B. in biomedizinischen Anwendungen, wenn gleichzeitig funktionale und anatomische Datensätze untersucht werden. Zunächst wird der Stand der Technik in der Visualisierung zweidimensionaler Volumen dargelegt. Dabei sind besonders die folgenden Schwächen bestehender Verfahren erkennbar: - Schlechte räumliche Darstellung und schlechte Lokalisierbarkeit von Ausprägungen (bemerkenswerte Quantitäten einer Eigenschaft an einer Stelle). Beschränkung auf Datensätze aus speziellen Quellen oder spezielle Kombinationen von Datensätzen. - Prinzipbedingte Beschränkung einer Eigenschaft auf wenige kleine Regionen innerhalb der anderen Eigenschaft. Basierend auf diesen Defiziten werden die Anforderungen für ein besseres Visualisierungsverfahren herausgearbeitet, anhand derer ein neues Verfahren, dependent rendering genannt, entwickelt wird. Das Verfahren basiert auf der Annahme, dass bei der Visualisierung mehrerer Eigenschaften immer eine Eigenschaft als Referenz zur Lokalisierung dienen kann. Abhängig von der ersten kann eine weitere Eigenschaft visualisiert werden. Es werden drei Implementierungen des Verfahrens vorgestellt, die ersten beiden sind Prototypen, die dritte eine spezialisierte Anwendung für eine biomedizinische Visualisierungsplattform. Die Implementierungen veranschaulichen, dass sich das vorgestellte Verfahren gegenüber bestehenden Ansätzen besonders durch folgende Punkte auszeichnet: - Gute Lokalisierbarkeit von Ausprägungen bei gleichzeitiger guter räumlicher Darstellung des Objekts (z.B.: "Ist es auf der Oberfläche heiss oder innerhalb des Objekts?"). - Gleiche räumliche Ausdehnung beider Datensätze möglich. - Genereller Ansatz: Keine Beschränkung auf Datensätze aus speziellen Quellen oder auf spezielle Kombinationen von Datensätzen. Das vorgestellte Verfahren stellt daher einen bedeutenden Fortschritt in der Technik der Visualisierung zweier Eigenschaften eines Objekts dar.In this thesis, a new technique for the visualisation of two-dimensional volumes is presented. The term multi-dimensional volume is defined as a set of spatially three-dimensional data sets, each of them describing another property (a physical quality, e.g. density or temperature) of the same object. Thus, two-dimensional volumes describe two different properties of an object. They are used e.g. in biomedical imaging, where anatomical and functional data are examined jointly. First, the state of the art in the visualisation of two-dimensional volumes is presented. In the course of this, the following deficiencies of existing approaches become apparent: - Unsatisfactory 3D impression (it is difficult to mentally reconstruct the spatially three-dimensional object from the rendering) and difficult localisation of features (i.e. remarkable characteristics in the quantity of a property at a given location). - Restriction to data sets from particular origins or particular combinations of data sets. - By design, one property is restricted to only a few small regions inside the other property. Starting from these deficiencies, the requirements for a visualisation technique that overcomes these limitations are elaborated. These are then used to develop a new technique, called dependent rendering, which is based on the assumption that, when visualising two properties of an object, there is alway one property that can serve as a spatial reference for the other. The other property is then visualised in dependency on this reference. Three implementations of the technique are presented, the first two are prototypes, the third one is a specialised application for a biomedical visualisation platform. The implementations show that, compared to existing approaches, the presented technique especially stands out because of the following features: - Precise localisation of features combined with good 3D impression of the object (e.g. "Is it hot on the surface or only inside the object?"). - Both data sets can be extended over the same region. - General approach: No restriction to data sets from particular origins or particular combinations of data sets. The presented technique therefore represents an important advancement in the joint visualisation of two properties of an object