Browsing by Subject "Geographic Information System"

Now showing 1 - 3 of 3
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    Assessing the accuracy of GIS-derived stream length and slope estimates
    (2012-12) Kocian, Matthew James
    Stream slope is a critical component in lotic systems research. It is commonly associated with fish and invertebrate distribution, and is prominently used in many stream classification schemes. Stream slope is also required to compute other stream variables, such as stream power, a fundamental component in stream sediment dynamics. Due to its importance, stream slope is regularly estimated remotely using a Geographic Information System (GIS). However, the accuracy of GIS-derived stream slope estimates is not well established, especially in low-slope regions. Additionally, little is known about variables that may influence the accuracy of GIS-derived slope estimates. In this study, the accuracy of eight GIS methods for estimating stream slope was evaluated by comparison to "true" field-surveyed values. Several novel GIS methods for estimating stream slope are presented. Five stream variables were assessed for their contribution to error in GIS-derived stream slope estimates. To demonstrate practical applicability, GIS-derived stream slope estimates were used to calculate stream power. GIS-derived stream slope estimates produced using 1:24,000 USGS topographic maps and Light Detection and Ranging (LiDAR) Digital Elevation Models (DEMs) were most accurate. Estimates derived from 1- and 1/3-Arc Second National Elevation Dataset DEMs were less accurate. The application of a focal statistics tool to LiDAR-derived DEMs improved stream slope estimate accuracy. Consistent sources of error in GIS stream slope estimates were not identified. The utility of GIS-derived stream slope estimates was demonstrated by presenting an association between stream power and depth of fine sediment.
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    A geospatial analysis of West Nile virus in the Twin Cities metropolitan area of Minnesota.
    (2009-07) Ghosh, Debarchana
    The West Nile virus (WNV) is an infectious disease transmitted to humans and other mammals by mosquitoes that acquire the virus by feeding on WNV-infected birds. Since its initial occurrence in New York in 1999, the virus has spread rapidly west and south, causing seasonal epidemics and illness among thousands of birds, animals, and humans. Yet, we only have a rudimentary understanding of how the mosquito-borne virus operates in complex avian-human-environmental systems. The virus first reached Minnesota in 2002 and resulted in several hotspots by 2003. The year 2007 saw one of the severest incidences of WNV in Minnesota. For my dissertation research, I have developed novel approaches to understand the spread and dynamics of the virus by using key environmental, built environment, and anthropogenic risk factors that determine why, when, and where WNV strikes in the Twin Cities Metropolitan area (TCMA). The first study demonstrates the use of a novel spatiotemporal approach to identify exposure areas. The method retrospectively delineates transmission cycles as exposure areas in their entirety, involving dead birds, mosquito pools, and human cases. Given the strong spatial clustering of WNV infections in the urban areas of TCMA, the next study explores how urban landscape features contributed to the viral activities. This investigation contributed to the broader research question in the field of health geography, of how the heterogeneous urban landscape affects human health and disease patterns. The remaining studies focus on the building and interpreting a nonlinear model which captures the complex relationships between the disease incidences and the hypothesized risk factors. The goal of these studies is to identify risk factor(s) whose management would result in effective disease prevention and containment. This dissertation has applied contributions to the vector control policies. The findings from the studies can answer two fundamental questions to eliminate larva and adult mosquitoes capable of carrying WNV. First, when is the optimal time to apply insecticides and pesticides? Second, where (area) should we target spraying of pesticides? This will lead to efficient allocation of resources and allow a balance between mosquito eradication and environmental conservation efforts with respect to insecticide usage.
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    Multiuse, High Accuracy, High Density Geospatial Database
    (University of Minnesota Center for Transportation Studies, 2009-02) Newstrom, Brian; Olson, Curtis
    High accuracy (2-8 cm) DGPS and high accuracy (5-20 cm) geospatial databases (or to use the term loosely, “enhanced digital maps”) are the primary components of the IV Lab driver assistive systems. In addition to vehicle-based systems, the IV Lab geospatial database has found utility in other applications. For instance, the database has recently been used for a new Intersection Decision Support (IDS) project, where radar sensors are used to determine the state of an intersection as a first step in warning drivers when it is unsafe to enter a thu-Stop intersection. The geospatial database is used in this application to improve the ability of the radar system to determine whether a target represents a legitimate threat at the intersection. The IV Lab geospatial database was designed and optimized for vehicle applications, and provides real time access to extremely accurate, dense geospatial data. Because of this optimization, its functionality in other applications is somewhat limited. As new applications arise (i.e., the need to integrate high accuracy geospatial data into a driving simulator, the desire by DOTs to more accurately represent roads, rights of way, etc.), a more “global” approach to the design of the existing geospatial database is required. Described herein is a redesign of the geospatial database and database manager and the development of a new “front end” to serve a wide application base.