Dynamic simplification and visualization of large maps

In this paper, we present an algorithm that performs simplification of large geographical maps through a novel use of graphics hardware. Given a map as a collection of non-intersecting chains and a tolerance parameter for each chain, we produce a simplified map that resembles the original map, satisfying the condition that the distance between each point on the simplified chain and the original chain is within the given tolerance parameter, and that no two chains intersect. In conjunction with this, we also present an out-of-core system for interactive visualization of these maps. We represent the maps hierarchically and employ different pruning strategies to accelerate the rendering. Our algorithm uses a parallel approach to do rendering as well as fetching data from the disk in a synchronous manner. We have applied our algorithm to a gigabyte sized map dataset. The memory overhead of our algorithm (the amount of main memory it requires) is output sensitive and is typically tens of megabytes, much smaller than the actual data size

Innovative Approaches to 3D GIS Modeling for Volumetric and Geoprocessing Applications in Subsurface Infrastructures in a Virtual Immersive Environment

As subsurface features remain largely ‘out of sight, out of mind’, this has led to challenges when dealing with underground space and infrastructures and especially so for those working in GIS. Since subsurface infrastructure plays a major role in supporting the needs of modern society, groups such as city planners and utility companies and decision makers are looking for an ‘holistic’ approach where the sustainable use of underground space is as important as above ground space. For such planning and management, it is crucial to examine subsurface data in a form that is amenable to 3D mapping and that can be used for increasingly sophisticated 3D modeling. The subsurface referred to in this study focuses particularly on examples of both shallow and deep underground infrastructures. In the case of shallow underground infrastructures mostly two-dimensional maps are used in the management and planning of these features. Depth is a very critical component of underground infrastructures that is difficult to represent in a 2D map and for this reason these are best studied in three-dimensional space. In this research, the capability of 3D GIS technology and immersive geography are explored for the storage, management, analysis, and visualization of shallow and deep subsurface features

Visualization algorithm for CSG polyhedral solids

International audienceAn algorithm is presented here to visualize here to visualize CSG solids in wireframe with hidden faces eliminated. The approach taken is to construct the image of the CSG solid directly from the CSG tree. This algorithm takes into account the face coherence property and the depth of the faces to minimize the number of rays fired during the process. It mixes a two-dimensional polygonal clipping and a ray-casting algorithm

The micrometeoroid complex and evolution of the lunar regolith

The interaction of the micrometeoroid complex with the lunar surface is evidenced by numerous glass-lined microcraters on virtually every lunar surface exposed to space. Such craters range in size from less than .1 micron to approximately 2 sq cm diameter. Using small scale laboratory cratering experiments for calibration, the observed crater-sized frequency distributions may be converted into micrometeoroid mass distributions. These lunar mass distributions are in essential agreement with satellite data. Some physical properties of micrometeoroids may be deduced by comparing lunar crater geometries with those obtained in laboratory experiments. The proponderance of circular outlines of lunar microcraters necessitates equidimensional, if not spherical, micrometeoroids

Nano-structured sorbents for rapid response interior air humidity buffering applications

Within a closed environment, (e.g. building, car, aircraft) that is thermally and hygrically isolated from the exterior climate, one approach that can help reduce the energy required for indoor mechanical climate control whilst increasing comfort levels for occupants is to use hygrothermal coatings on top of existing materials. Hygrothermal coatings can re-introduce both thermal and hygric buffering within the isolated envelope. Understanding of the behaviour of these coatings allows them to be optimized for different environments. The overall aim of the research is to design the functional properties of inorganic, nano structured surface coatings i.e. mesoporous silica (MS) to produce desired hygrothermal behavioural responses to climatic variables in a controlled environment. This can be achieved through correlation of the hygrothermal properties of desiccant materials with their microstructural characteristics and understanding the hygrothermal behaviour of the materials under representative psychrometric conditions. Stage 1 was to characterise the hygrothermal properties of the MS and other conventional desiccant materials i.e. Silica Gel, Molecular Sieve, Clinoptilolite and Bentonite to produce a ‘Template of functional properties’ and provide material input data for the numerical models. These tests included dynamic vapour sorption (DVS) techniques for moisture absorption including cyclic adsorption/desorption and sorption isotherms, wet-cup tests for vapour permeability, partial immersion tests for liquid water absorption, modified transient plane source (MTPS) tests for thermal conductivity and differential scanning calorimetry (DSC) for heat capacity. Stage 2 utilised techniques to classify the pore geometry of the desiccants, including helium pycnometry for solid density, gravimetric testing for bulk density, N2 physisorption for specific surface area, mesopore volume and mean pore diameter with small angle X-ray scattering and transmission electron microscopy used to corroborate the N2 results. Scanning electron microscopy (SEM) was used to confirm material composition and purity and to indicate macropore distribution. A correlation between the hygrothermal properties from Stage 1 with their microstructural characteristics was then sought. Stage 3 was a parametric analysis of the candidate materials hygrothermal behaviour using the validated 1D numerical simulation software WUFI Pro v5.1. Further analysis was carried out to assess how the numerical model could be used to tune the functional properties of the MS materials to suit differing psychrometric conditions in closed environments. A series of simulations using a representative climate (Nottingham) were also run to compare the hygrothermal behaviour of the MS materials to the conventional desiccants A series of energetic 3D physical and numerical models (WUFI Plus v 2.1) were designed to study the resultant relative humidity levels in both occupied and unoccupied spaces and under different air exchange rates due to the presence of the hygrothermal materials in a closed environment. The 3D model was also used to compare the operational energy usage of different retrofitting cases under the same representative climate used in Stage 3 with three different heating, cooling humidification and dehumidification (HCHD) control scenarios. The MS materials displayed significantly higher Moisture Buffer Values (MBV), equilibrium moisture contents (EMC) and faster response rates when compared to the conventional desiccants. It was shown that WUFI Pro can be used as a design tool for material functional properties, with the sorption isotherm, and in particular adjustment of the w50 – w80 gradient of the absorption branch isotherm being by far the most sensitive parameter. In the MS samples, the dynamic vapour sorption (DVS) response time has a significant and positive logarithmic relationship with both the mesopore diameter and the mesopore volume implying that mesopore geometry can be tuned in order to give the desired dynamic vapour sorption/ desorption response rate and storage capacity to suit a given set of interior psychrometric conditions. It is therefore possible to tune an MS material to suit a particular set of psychrometric conditions using WUFI Pro. The MS materials displayed outstanding passive buffering performance across a range of exterior climate conditions combined with numerous internal moisture and ventilation overloading scenarios, providing constant humidity buffering within the American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE) comfort limits. When compared against a retro-fitted gypsum-lined indoor environment there was a potential reduction in humidification/ dehumidification energy demand of up to 100% when using an MS material coating

Synthetic movies

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Architecture, 1989.Includes bibliographical references (leaves 67-70).by John A. Watlington.M.S