Christopher J. Crosby

CyberGIS software: a synthetic review and integration roadmap

CyberGIS – defined as cyberinfrastructure-based geographic information systems (GIS) – has emerged as a new generation of GIS representing an important research direction for both cyberinfrastructure and geographic information science. This study introduces a 5-year effort funded by the US National Science Foundation to advance the science and applications of CyberGIS, particularly for enabling the analysis of big spatial data, computationally intensive spatial analysis and modeling (SAM), and collaborative geospatial problem-solving and decision-making, simultaneously conducted by a large number of users. Several fundamental research questions are raised and addressed while a set of CyberGIS challenges and opportunities are identified from scientific perspectives. The study reviews several key CyberGIS software tools that are used to elucidate a vision and roadmap for CyberGIS software research. The roadmap focuses on software integration and synthesis of cyberinfrastructure, GIS, and SAM by defining several key integration dimensions and strategies. CyberGIS, based on this holistic integration roadmap, exhibits the following key characteristics: high-performance and scalable, open and distributed, collaborative, service-oriented, user-centric, and community-driven. As a major result of the roadmap, two key CyberGIS modalities – gateway and toolkit – combined with a community-driven and participatory approach have laid a solid foundation to achieve scientific breakthroughs across many geospatial communities that would be otherwise impossible.

Illuminating Northern California's Active Faults

Newly acquired light detection and ranging (lidar) topographic data provide a powerful community resource for the study of landforms associated with the plate boundary faults of northern California (Figure 1). In the spring of 2007, GeoEarthScope, a component of the EarthScope Facility construction project funded by the U.S. National Science Foundation, acquired approximately 2000 square kilometers of airborne lidar topographic data along major active fault zones of northern California. These data are now freely available in point cloud (x, y, z coordinate data for every laser return), digital elevation model (DEM), and KMZ (zipped Keyhole Markup Language, for use in Google EarthTM and other similar software) formats through the GEON OpenTopography Portal (http://www.OpenTopography.org/data). Importantly, vegetation can be digitally removed from lidar data, producing high-resolution images (0.5- or 1.0-meter DEMs) of the ground surface beneath forested regions that reveal landforms typically obscured by vegetation canopy (Figure 2).

Evaluation of MapReduce for Gridding LIDAR Data

The MapReduce programming model, introduced by Google, has become popular over the past few years as a mechanism for processing large amounts of data, using shared-nothing parallelism. In this paper, we investigate the use of MapReduce technology for a local gridding algorithm for the generation of Digital Elevation Models (DEM). The local gridding algorithm utilizes the elevation information from LIDAR (Light, Detection, and Ranging) measurements contained within a circular search area to compute the elevation of each grid cell. The method is data parallel, lending itself to implementation using the MapReduce model. Here, we compare our initial C++ implementation of the gridding algorithm to a MapReduce-based implementation, and present observations on the performance (in particular, price/performance) and the implementation complexity. We also discuss the applicability of MapReduce technologies for related applications.

Paleoseismic and Postseismic Observations of Surface Slip along the Parkfield Segment of the San Andreas Fault

Parkfield is considered a transitional segment along the San Andreas fault (saf) between continuous fault creep to the northwest and segments to the southeast that last slipped in the great 1857 Fort Tejon earthquake. Historically, creep and recurring M 6.0 earthquakes have been observed at Parkfield, California, but the segment’s relevance in great saf earthquakes has remained uncertain. This paleoseismic study of the central Parkfield segment provides a >2000-year record of tectonically deformed fluvial and sag stratigraphy. Two fault-perpendicular excavations across a pressure ridge and a sag pond ∼200 m north of Carr Hill exposed five primary fault zones displaying apparent vertical offsets, upward splaying clay shear bands, and warped stratigraphy. Four of five fault zones extended into the uppermost stratigraphy, suggesting recent surface offset and fault creep. Several antithetic fault splays and one primary fault zone displayed upward terminations, but strong indicators of large-magnitude earthquakes with meter-scale surface offset and rupture such as filled fissures and colluvial scarp deposits were not observed. The absence of evidence for large-magnitude earthquakes does not preclude the possibility of 1857-style earthquakes extending into the Parkfield segment. However, all deformation exposed within these trenches is consistent with repeated small ground rupture and fault creep. The 2004 M 6.0 Parkfield earthquake ruptured through the site and activated at least three of the five fault zones exposed in our excavations. Comparison between 2004 vertical offset and vertical offsets within the exposed stratigraphy suggests a recurrence interval between 8 and 188 years for M 6.0 earthquakes at Parkfield. Online material : Supplemental unit descriptions, unanalyzed radiocarbon samples, and trench logs and photos.

A three tier architecture for LiDAR interpolation and analysis

Emerging Grid technologies enable solving scientific problems that involve large datasets and complex analyses. Coordinating distributed Grid resources and computational processes requires adaptable interfaces and tools that provide a modularized and configurable environment for accessing Grid clusters and executing high performance computational tasks. In addition, it is beneficial to make these tools available to the community in a unified framework through a shared cyberinfrastructure, or a portal, so scientists can focus on their scientific work and not be concerned with the implementation of the underlying infrastructure. In this paper we describe a scientific workflow approach to coordinate various resources as data analysis pipelines. We present a three tier architecture for LiDAR interpolation and analysis, a high performance processing of point intensive datasets, utilizing a portal, a scientific workflow engine and Grid technologies. Our proposed solution is available through the GEON portal and, though focused on LiDAR processing, is applicable to other domains as well.

Leveraging XSEDE HPC resources to address computational challenges with high-resolution topography data

Leveraging service-oriented architectures and taking advantage of the high-performance compute resources provided by XSEDE, we have developed standards-based web services to address the challenges associated with processing large volumes of high resolution topography data. These web services make results from community software packages and other cyberinfrastructure-based applications available to the wider earth sciences community via the OpenTopography Facility and the CyberGIS Gateway.

Geomorphology, denudation rates, and stream channel profiles reveal patterns of mountain building adjacent to the San Andreas fault in northern California, USA

Relative horizontal motion along strike-slip faults can build mountains when motion is oblique to the trend of the strike-slip boundary. The resulting contraction and uplift pose off-fault seismic hazards, which are often difficult to detect because of the poor vertical resolution of satellite geodesy and difficulty of locating offset datable landforms in active mountain ranges. Sparse geomorphic markers, topographic analyses, and measurement of denudation allow us to map spatiotemporal patterns of uplift along the northern San Andreas fault. Between Jenner and Mendocino, California, emergent marine terraces found southwest of the San Andreas fault record late Pleistocene uplift rates between 0.20 and 0.45 mm yr−1 along much of the coast. However, on the northeast side of the San Andreas fault, a zone of rapid uplift (0.6−1.0 mm yr−1) exists adjacent to the San Andreas fault, but rates decay northeastward as the coast becomes more distant from the San Andreas fault. A newly dated 4.5 Ma shallow-marine deposit located at ∼500 m above sea level (masl) adjacent to the San Andreas fault is warped down to just 150 masl 15 km northeast of the San Andreas fault, and it is exposed at just 60−110 masl to the west of the fault. Landscape denudation rates calculated from abundance of cosmogenic radionuclides in fluvial sediment northeast of, and adjacent to, the San Andreas fault are 0.16−0.29 mm yr−1, but they are only 0.03−0.07 mm yr−1 west of the fault. Basin-average channel steepness and the denudation rates can be used to infer the erosive properties of the underlying bedrock. Calibrated erosion rates can then be estimated across the entire landscape using the spatial distribution of channel steepness with these erosive properties. The lower-elevation areas of this landscape that show high channel steepness (and hence calibrated erosion rate) are distinct from higher-elevation areas with systematically lower channel steepness and denudation rates. These two areas do not appear to be coincident with lithologic contacts. Assuming that changes in rock uplift rates are manifest in channel steepness values as an upstream-propagating kinematic wave that separates high and low channel steepness values, the distance that this transition has migrated vertically provides an estimate of the timing of rock uplift rate increase. This analysis suggests that rock uplift rates along the coast changed from 0.3 to 0.75 mm yr−1 between 450 and 350 ka. This zone of recent, relatively rapid crustal deformation along the plate boundary may be a result of the impingement of relatively strong crust underlying the Gualala block into the thinner, weaker oceanic crust left at the western margin of the North American plate by the westward migration of the subduction zone prior to establishment of the current transform plate boundary. The warped Pliocene marine deposits and the presence of a topographic ridge support the patterns indicated by the channel steepness analyses, and further indicate that the zone of rapid uplift may herald elevated off-fault seismic hazard if this uplift is created by periodic stick-slip motion on contractional structures.

Scaling GIS analysis tasks from the desktop to the cloud utilizing contemporary distributed computing and data management approaches: A case study of project-based learning and cyberinfrastructure concepts

In this paper we present the experience of scaling in parallel a geographic information system modeling framework to hundreds of processors. The project began in an active learning cyberinfrastructure course which was followed by an XSEDE ECSS effort in collaboration across multiple-institutions.

Geoinformatics: Scientific workflows for the geosciences: An emerging approach to building integrated data analysis systems

Scientific method and the influence of technology Due to the increasing number and sophistication of data acquisition technologies, the amount of raw data acquired has vastly increased over the last couple of decades (Berman, 2008). This explosion of scientific data, growth in scientific knowledge, and the increase in the number of studies that require access to knowledge from multiple scientific disciplines amplify the complexity of scientific problems. In order to answer these “grand challenge” scientific questions, scientists use computational methods that are evolving almost daily. The basic scientific method, however, remains the same for the individual scientist. Scientists still start with a set of questions, then observe phenomena, gather data, develop hypotheses, perform tests, negate or modify hypotheses, reiterate the process with various data, and finally come up with a new set of questions, theories, or laws (http://en.wikipedia.org/wiki/Scientific_method). A recent change in this scientific method is that it is continuously being transformed with the advances in computer science and technology. The simplest examples of this transformation are use of personal computers to record scientific activity and the way scientists publish and search for publications online. More advanced technologies within the scientific process include sensor-based observatories to collect data in real time, supercomputers to run simulations, domain-specific data archives that give access to heterogeneous data, and online interfaces to distribute computational experiments and monitor resources.

A three tier architecture applied to LiDAR processing and monitoring

Emerging Grid technologies enable solving scientific problems that involve large datasets and complex analyses, which in the past were often considered difficult to solve. Coordinating distributed Grid resources and computational processes requires adaptable interfaces and tools that provide modularized and configurable environments for accessing Grid clusters and executing high performance computational tasks. Computationally intensive processes are also subject to a high risk of component failures and thus require close monitoring. In this paper we describe a scientific workflow approach to coordinate various resources via data analysis pipelines. We present a three tier architecture for LiDAR interpolation and analysis, a high performance processing of point intensive datasets, utilizing a portal, a scientific workflow engine and Grid technologies. Our proposed solution is available to the community in a unified framework through a shared cyberinfrastructure, the GEON portal, enabling scientists to focus on their scientific work and not be concerned with the implementation of the underlying infrastructure.