Novel findings on the dilatancy and non-coaxiality of sand under generalised loading

Acta Geotechnica - The dilatancy and non-coaxiality of sand are investigated under generalised loading including rotation of the stress principal axes (PA), in drained and undrained conditions....     

Low Cost Digital Rectification on A PC

Digital photogrammetric techniques have opened fresh horizons and have enabled photogrammetry to become a more user friendly tool for a wide range of applications. However cost remains a critical issue, because new digital photogrammetric workstations and their related software are considered expensive. This paper examines the problem of digital rectification and presents low cost solutions involving the use of commercial off the shelf software packages, which include graphics and painting software, image processing tools and a CAD system. Additionally, specially developed software performing vector rectification is described and discussed. All the packages have been used for rectifying digital images and the results are presented. An attempt is also made to assess the accuracy and reliability of the results. Finally, several alternative digital products are presented, mainly concerning the use of the methods described in the restitution of cultural monuments.     

Distribution of suspended particulate matter determined by in-situ observations and satellite images in the NW Aegean Sea (Greece)

Suspended particulate matter (SPM) patterns in the surface waters of the NW Aegean Sea were studied by (1) determining SPM concentration by water filtration, (2) measuring light transmission, and (3) evaluating satellite images. The SPM signals of the three major rivers discharging into the study area were recorded by all three methods, thereby providing information about the sources, transport pathways, and regional dispersion patterns of the SPM. The filtration of water samples and light transmission measurements were found to be good indicators of SPM concentrations in surface waters. Most of the SPM is composed of terrigenous minerals, thus explaining the correlation between the beam attenuation coefficient and the SPM concentration. A Landsat image obtained for the study period was found to adequately reveal regions with high SPM concentrations. Low concentrations, on the other hand, remain obscured. Received: 3 August 1999 / Revision accepted: 15 March 2000     

Three Dimensional Visualization of the Built Environment Using Digital Orthophotography

In this paper, different ways of performing large scale mapping of built up areas are discussed. Emphasis is placed on large scale representation through digital orthophotographs as the visualization medium of the real world. In an application, the process of creating perspective views of an orthophotograph draped on the digital terrain model of the study area is described; these views include the blocks of the built environment as three dimensional objects. The cartographic product is derived from a pair of overlapping aerial photographs processed through photogrammetric and GIS software packages. Finally, the perspective view of the digital orthophotograph is assessed as a large scale visualization tool for the communication of spatial information.