Charles W. Grant

Visualizing 3D velocity fields near contour surfaces

Vector field rendering is difficult in 3D because the vector icons overlap and hide each other. We propose four different techniques for visualizing vector fields only near surfaces. The first uses motion blurred particles in a thickened region around the surface. The second uses a voxel grid to contain integral curves of the vector field. The third uses many antialiased lines through the surface, and the fourth uses hairs sprouting from the surface and then bending in the direction of the vector field. All the methods use the graphics pipeline, allowing real time rotation and interaction, and the first two methods can animate the texture to move in the flow determined by the velocity field.<<ETX>>

Integrated analytic spatial and temporal anti-aliasing for polyhedra in 4-space

A visible surface algorithm with integrated analytic spatial and temporal anti-aliasing is presented. This algorithm models moving polygons as four dimensional (X,Y,Z,T) image space polyhedra, where time (T) is treated as an additional spatial dimension. The linearity of these primitives allows simplification of the analytic algorithms. The algorithm is exact for non-intersecting primitives, and exact for the class of intersecting primitives generated by translation and scaling of 3-d (X,Y,Z) polygons in image space. This algorithm is an extension of Catmulls analytic visible surface algorithm for independent pixel processing, based on the outline of integrated spatial and temporal anti-aliasing given by Korien and Badler. An analytic solution requires that the visible surface calculations produce a continuous representation of visible primitives in the time and space dimensions. Visible surface algorithm, graphical primitives, and filtering algorithm, (by Feibush, Levoy and Cook) are extended to include continuous representation of the additional dimension of time. A performance analysis of the algorithm contrasted with a non-temporally anti-aliased version is given.

The impact of climate change on vadose zone pore waters and its implication for long-term monitoring

Protecting groundwater is of growing interest as pressure on these resources grows. Recharge of groundwater takes place through the vadose zone, where complex interactions between thermal-hydrological-geochemical processes affect water quality. Monitoring processes in the vadose zone is an important means of evaluating the long-term health of aquifer systems, and has become an integral part of many subsurface engineering efforts. Monitoring such systems, however, may be affected by changes in climate that slowly propagate through vadose zone systems. We describe in this paper the use of NUFT-C, a reactive transport simulator designed to run on a high performance, massively parallel computer, to compare quantitatively the evolution of a deep vadose zone with changes expected from an engineered high-level nuclear waste repository. The results suggest that the impacts from waste emplacement are, in some instances, similar to those that would be observed as a result of climate change, whereas others are distinguishable from evolution of the natural system. Such simulations facilitate design of long-term monitoring programs that take account of these complex effects. The results emphasize the importance of developing long-term baseline measurements and control sites, in order to enhance confidence in interpretations of complexly evolving data sets that will be obtained from multidecade monitoring efforts.

The Impact of Climate Change on the Chemical Composition of Deep Vadose Zone Waters

is a product of those physical and chemical interactions that take place among water, mineral surfaces, and pore Chloride mass balance, and stable (deuterium and 18O) and radiogas in the unsaturated zone (Faybishenko, 2000). If genic (3H, 36Cl) isotope studies of deep vadose zone pore waters have generally concluded that variations in moisture flux can account for the moisture flux varies in the vadose zone as a result of observed variations in abundance of these approximately conservative variation in climate, it is likely that the dissolved load tracers. It can be inferred, on the basis of these observations and in vadose zone pore waters will also vary in sympathetic interpretations, that a climate change record is preserved in these ways. It is the purpose of this paper to evaluate the vadose zone waters. In arid regions where thick ( 100 m) vadose magnitude and extent of this potential sympathetic varizones persist, it has been concluded that this record may extend back ation using published data and simulations of reactive more than 100 000 yr. Consideration of the mechanisms that control transport in the vadose zone. The conclusion is reached reactive transport led to the conclusion that such climate-driven effects that significant changes in the composition of vadose will also be evident as chemical reactions involving dissolution and/ zone pore waters should occur in response to climateor precipitation of mineral phases along the flow pathway. As a result, forced changes in infiltration flux and surface temperathere should also be variations in the concentrations of nonconservative chemical species that correspond to changes in the concentrations ture. As a result, there is a potentially rich archive of of the conservative tracers. Simulations of this reactive transport, in regional-scale climate change data preserved within a regime typical of the arid U.S. Southwest, demonstrate that these large regions of most continental land masses. However, changes can modify pore water chemistry by factors of up to 200%, interpreting empirical pore water chemical composibut the changes take place slowly, requiring thousands of years to tions in terms of past climate change is currently probachieve steady-state conditions. This suggests that a very rich archive lematic because of uncertainties in key parameters that of climate change history is preserved in this type of setting. However, control the chemical kinetics and the hydrologic history. extracting that history is currently hampered by limitations in data and models (e.g., effective mineral reactive surface areas, fluid flow Background pathways, and quantified models of wetted fracture surface in unsaturated, fractured systems). This challenge may be overcome if coordiThat vadose zone pore waters may preserve a nonconnated efforts are undertaken that exploit the power of detailed studies servative chemical signature of climate change is implicit of isotope systematics, microscale rock characterization, and high in two lines of reasoning. One line of reasoning, which performance computing. considers time variation of water flux across the land surface boundary layer, suggests that changes in climatedriven moisture flux are preserved in the vadose zone D the last quarter century, research that as slowly migrating variations in concentration of the has examined the distribution of “conservative” solute load. The second line of reasoning, which considtracers in vadose zone pore waters has concluded that ers the kinetics of dissolution and precipitation reactions this geological setting preserves a record of local moisin the vadose zone, implies that the reactions that are ture flux (Allison et al., 1985; Barnes and Allison, 1988; responsible for the evolution of pore water chemical Cook et al., 1989, 1994; Dettinger, 1989; Scanlon, 1991; characteristics may be responsive to changes in the land Walker et al., 1991). In arid environments, where the surface temperature and infiltration flux boundary convadose zone can be hundreds of meters thick, and infilditions. Both of these considerations are discussed below. tration fluxes are low, it has been inferred that this record may extend as much as 100 000 yr into the past Variability of Moisture Flux Through the Vadose Zone (Tyler et al., 1996). If this conclusion is correct, the potential exists to reconstruct moisture flux records on The analysis of diverse chemical tracers in pore waters continental land masses in many parts of the world. If has allowed development of conceptual models useful moisture flux can be treated as a proxy for changes in for quantifying the temporal record of water movement precipitation, then the possibility exists that long-term rates and residence times in the vadose zone. Chloride climate records may exist in some vadose zone settings. was among the first tracers to support such an effort. The chemical composition of vadose zone pore water As the chemical characteristics of Cl-bearing aerosols became better understood (e.g., Winchester and Duce, W.E. Glassley, J.J. Nitao, and C.W. Grant, Lawrence Livermore Na1967), and deposition of chloride on land surfaces was tional Laboratory, Livermore CA 94550. Received 25 Jan. 2002. *Corconceptualized, use of chloride as a tracer for water responding author (glassley1@llnl.gov). movement in vadose zones became relatively common (e.g., Allison et al., 1985; Barnes and Allison, 1988; Published in Vadose Zone Journal 1:3–13 (2002).

A visual wikipedia for satellite imagery

GeoVisipedia (Geospatial Visual Wikipedia) is a new and novel approach to sharing knowledge about complex geospatial entities such as facilities. Facilities are composed of interconnected objects such as buildings, chemical processing units, electrical generation equipment and similar structures. Satellite imagery of a facility reveals a great deal about the organization and visual appearance of objects in a facility, but very little about the identity or function of the object. For example, given a satellite imagery of an oil refinery, an expert in refining readily identifies distillation units and can explain how they work. A non-expert would have a very difficult time identifying these objects let alone explaining how they function. To make highly complex information accessible to non-experts, GeoVisipedia associates a wiki page with objects in satellite imagery. A user selects an object in the image and a wiki page appears that provides the user with detailed information about the object. Experts can author information into the wiki and this information is shared with other users. Additionally, GeoVisipedia automatically transfers all wiki pages from one image of a facility to other imagery of the facility. Consequentially, knowledge about objects in the facility integrates over time as new imagery becomes available and as new wiki pages are created and additional information is added to existing wiki pages. In this respect, satellite imagery becomes a portal to expert knowledge and insight about objects in a facility.

Weighted model components for gradient direction matching in overhead images

Gradient direction matching (GDM) is the main target identification algorithm used in the Image Content Engine project at Lawrence Livermore National Laboratory. GDM is a 3D solid model-based edge-matching algorithm which does not require explicit edge extraction from the source image. The GDM algorithm is presented, identifying areas where performance enhancement seems possible. Improving the process of producing model gradient directions from the solid model by assigning different weights to different parts of the model is an extension tested in the current study. Given a simple geometric model, we attempt to determine, without obvious semantic clues, if different weight values produce significantly better matching accuracy, and how those weights should be assigned to produce the best matching accuracy. Two simple candidate strategies for assigning weights are proposed: pixel-weighted and edge-weighted. We adjust the weights of the components in a simple model of a tractor/semi-trailer using relevance feedback to produce an optimal set of weights for this model and a particular test image. The optimal weights are then compared with pixel and edge-weighting strategies to determine which is most suitable and under what circumstances.

Image Content Engine (ICE): A System for Fast Image Database Searches

The Image Content Engine (ICE) is being developed to provide cueing assistance to human image analysts faced with increasingly large and intractable amounts of image data. The ICE architecture includes user configurable feature extraction pipelines which produce intermediate feature vector and match surface files which can then be accessed by interactive relational queries. Application of the feature extraction algorithms to large collections of images may be extremely time consuming and is launched as a batch job on a Linux cluster. The query interface accesses only the intermediate files and returns candidate hits nearly instantaneously. Queries may be posed for individual objects or collections. The query interface prompts the user for feedback, and applies relevance feedback algorithms to revise the feature vector weighting and focus on relevant search results. Examples of feature extraction and both model-based and search-by-example queries are presented.