Spatial analysis of within-vineyard grapevine sensitivity to solar irradiance patterns. A case study using Pinot noir in a complex terrain

Communication orale, texte intégralWe analyze how the patterns of the solar irradiance affect the growth of Pinot noir grapevines at stand-scale over a hilly terrain bounded by a coniferous forest. Results show that the patterns of irradiance deficit are the primary driving force of the growth. Linear trends display good correlation between the total deficit of irradiance, and the developed growth index (R2 up to 0.96 ). This result also suggests the impact of low minimum temperature due to cold air drainage and stagnation. Results lead to propose a model able to capture at stand-scale 90% of the whole spatial variability of the growth. The model accounts for the diffuse component of the deficit of irradiance and the squared temperature anomalies. Combining such models through the use of GIS enables to better understand the driving mechanisms of grapevine growth over complex terrain, towards a better management of the “terroir” potential whithin climate change

Total 3D-viewshed map: quantifying the visible volume in digital elevation models

The 3D perception of the human eye is more impressive in irregular land surfaces than in flat land surfaces. The quantification of this perception would be very useful in many applications. This article presents the first approach to determining the visible volume, which we call the 3D-viewshed, in each and all the points of a DEM (Digital Elevation Model). Most previous visibility algorithms in GIS (Geographic Information Systems) are based on the concept of a 2D-viewshed, which determines the number of points that can be seen from an observer in a DEM. Extending such a 2D-viewshed to 3D space, then to all the DEM-points, is too expensive computationally since the viewshed computation per se is costly. In this work, we propose the first approach to compute a new visibility metric that quantifies the visible volume from every point of a DEM. In particular, we developed an efficient algorithm with a high data and calculation re-utilization. This article presents the first total-3D-viewshed maps together with validation results and comparative analysis. Using our highly scalable parallel algorithm to compute the total-3D-viewshed of a DEM with 4 million points on a Xeon Processor E5-2698 takes only 1.3 minutes

A data relocation approach for terrain surface analysis on multi-GPU systems: a case study on the total viewshed problem

Digital Elevation Models (DEMs) are important datasets for modelling the line of sight, such as radio signals, sound waves and human vision. These are commonly analyzed using rotational sweep algorithms. However, such algorithms require large numbers of memory accesses to 2D arrays which, despite being regular, result in poor data locality in memory. Here, we propose a new methodology called skewed Digital Elevation Model (sDEM), which substantially improves the locality of memory accesses and increases the inherent parallelism involved in the computation of rotational sweep-based algorithms. In particular, sDEM applies a data restructuring technique before accessing the memory and performing the computation. To demonstrate the high efficiency of sDEM, we use the problem of total viewshed computation as a case study considering different implementations for single-core, multi-core, single-GPU and multi-GPU platforms. We conducted two experiments to compare sDEM with (i) the most commonly used geographic information systems (GIS) software and (ii) the state-of-the-art algorithm. In the first experiment, sDEM is on average 8.8x faster than current GIS software despite being able to consider only few points because of their limitations. In the second experiment, sDEM is 827.3x faster than the state-of-the-art algorithm in the best case

Placing the Pillar of Eliseg: Movement, Visibility and Memory in the Early Medieval Landscape

This is an Accepted Manuscript of an article published by Taylor & Francis in Medieval Archaeology on 19/06/2017, available online: http://dx.doi.org/10.1080/00766097.2017.1295926The landscape context of the early 9th-century monument known as the Pillar of Eliseg is interrogated here for the first time with GIS-based analysis and innovative spatial methodologies. Our interpretation aims to move beyond regarding the Pillar as a prominent example of early medieval monument reuse and a probable early medieval assembly site. We demonstrate that the location and topographical context of the cross and mound facilitated the monument’s significance as an early medieval locus of power, faith and commemoration in a contested frontier zone. The specific choice of location is shown to relate to patterns of movement and visibility that may have facilitated and enhanced the ceremonial and commemorative roles of the monument. By shedding new light on the interpretation of the Pillar of Eliseg as a node of social and religious aggregation and ideological power, our study has theoretical and methodological implications for studying the landscape contexts of early medieval stone monuments

Hierarchical occlusion culling for arbitrarily-meshed height fields

Many graphics applications today have need for high-speed 3-D visualization of height fields. Most of these applications deal with the display of digital terrain models characterized by a simple, but vast, non-overlapping mesh of triangles. A great deal of research has been done to find methods of optimizing such systems. The goal of this work is to establish an algorithm to efficiently preprocess a hierarchical height field model that enables the real-time culling of occluded geometry while still allowing for classic terrain-rendering frameworks. By exploiting the planar-monotone characteristics of height fields, it is possible to create a unique and efficient occlusion culling method that is optimized for terrain rendering and similar applications. Previous work has shown that culling is possible with certain regularly-gridded height field models, but not until now has a system been shown to work with all height fields, regardless of how their meshes are constructed. By freeing the system of meshing restrictions, it is possible to incorporate a number of broader height field algorithms with widely-used applications such as flight simulators, GIS systems, and computer games

A Framework for Dynamic Terrain with Application in Off-road Ground Vehicle Simulations

The dissertation develops a framework for the visualization of dynamic terrains for use in interactive real-time 3D systems. Terrain visualization techniques may be classified as either static or dynamic. Static terrain solutions simulate rigid surface types exclusively; whereas dynamic solutions can also represent non-rigid surfaces. Systems that employ a static terrain approach lack realism due to their rigid nature. Disregarding the accurate representation of terrain surface interaction is rationalized because of the inherent difficulties associated with providing runtime dynamism. Nonetheless, dynamic terrain systems are a more correct solution because they allow the terrain database to be modified at run-time for the purpose of deforming the surface. Many established techniques in terrain visualization rely on invalid assumptions and weak computational models that hinder the use of dynamic terrain. Moreover, many existing techniques do not exploit the capabilities offered by current computer hardware. In this research, we present a component framework for terrain visualization that is useful in research, entertainment, and simulation systems. In addition, we present a novel method for deforming the terrain that can be used in real-time, interactive systems. The development of a component framework unifies disparate works under a single architecture. The high-level nature of the framework makes it flexible and adaptable for developing a variety of systems, independent of the static or dynamic nature of the solution. Currently, there are only a handful of documented deformation techniques and, in particular, none make explicit use of graphics hardware. The approach developed by this research offloads extra work to the graphics processing unit; in an effort to alleviate the overhead associated with deforming the terrain. Off-road ground vehicle simulation is used as an application domain to demonstrate the practical nature of the framework and the deformation technique. In order to realistically simulate terrain surface interactivity with the vehicle, the solution balances visual fidelity and speed. Accurately depicting terrain surface interactivity in off-road ground vehicle simulations improves visual realism; thereby, increasing the significance and worth of the application. Systems in academia, government, and commercial institutes can make use of the research findings to achieve the real-time display of interactive terrain surfaces