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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
181

GIS Tools to Improve the Transit Planning Process

Springate, Erica January 2011 (has links)
Public transit provides an important community service by reducing pollution, traffic congestion, and by providing transportation for those who do not or cannot drive. Yet since the 1950s, real investment levels in transit have declined in many North American cities which has resulted in diminished service levels and ridership. In order for transit agencies to attract more riders, transit service must be competitive with alternative modes of transport, particularly private automobiles. However, since funding is limited, planning staff must ensure that the service changes that are implemented result in the greatest benefits to the system. This thesis presents an iterative approach to evaluating service changes in a transit network that combines the output from sophisticated transportation models, demographic data, and software analysis with local knowledge and expertise. The thesis focuses specifically on three common challenges in transit planning: quantifying costs of transfers between destinations within a system, examining access distances to transit as a measure of transit supportiveness, and estimating ridership changes resulting from small route adjustments. Three GIS-based tools, referred to as the Transfer, Access and Route Planning Tools, were developed to address these challenges and were demonstrated using transit system data from the Region of Waterloo in Southwestern Ontario. The Transfer Tool was used to highlight trips with high transfer costs to determine which changes in the route structure would result in the greatest reduction of the generalized cost of a trip attributed to transfers. Results from the Access Tool and Route Planning Tools demonstrated how changes to the streets along which transit routes operate influence access distances to transit, and further, transit ridership. The Access Tool also demonstrated how the design of the street network and the presence of pedestrian paths may affect access distances. Finally, this thesis concludes by recommending areas of future research.
182

Spatial variability of actual evaporation in a prairie landscape

Armstrong, Robert Norman 24 June 2011 (has links)
Land surface evaporation has considerable spatial variability that is not reflected in meteorological station data alone. Knowing the spatial variability of evaporation is important for describing drought, managing agricultural land, and is valuable for improving the parameterization of hydrological models and land surface schemes over large areas. General difficulties arise for obtaining reliable, spatially distributed evaporation estimates as a result of uncertainty in estimation techniques, scale issues and complexities regarding land surface and atmospheric interactions, and the spatial and temporal variability of key factors governing the evaporation process. Estimating evaporation is further complicated when soil moisture becomes a critical limitation, particularly during drought. An examination of the spatial variability of evaporation and its association with governing factors was conducted in Prairie landscapes using three modelling techniques. First, eddy covariance measurements and reference meteorological data were obtained at two Prairie locations to assess the accuracy of physically-based models for calculating point estimates of actual evaporation under non-limited soil moisture conditions and during drought. Second, estimates of actual evaporation were distributed at the field scale in order to examine the impacts of driving factors and their spatial associations on upscaled evaporation estimates. This required the assimilation of high resolution visible and thermal images which were used to derive estimates of surface albedo and surface emitted longwave radiation. These were combined along with surface reference observations to develop an index of the mid-day radiation in order to distribute a known value of mean daily net radiation over the field. Third, archived historical climate data were used as input for a continuous hydrological simulation to examine spatial and temporal variations in evaporation across the Prairie region of Western Canada during a drought and non-drought period. Results of this research showed that the spatial variability of evaporation could be derived at the field scale by integrating remote sensing and surface reference climate data with a physically-based evaporation model. Surface temperature and soil moisture, and net radiation were found to be highly variable spatially at field scales whilst meteorological conditions tended to be less variable spatially but showed strong temporal variability. At the field scale it was found that the variability in albedo and surface temperature were both important for characterizing differences in surface state conditions. Their combined influence was reflected in the resulting pattern of net radiation that governed the distribution of actual evaporation estimates obtained with the Granger and Gray evaporation model. It was found that an areal estimate of evaporation obtained from the means of driving factors was similar to the areal average obtained from the distributed estimates. This was attributed to the offsetting interactions among the driving factors which effectively reduced the variability of the model estimates. In general, the physically-based models examined were found to provide reasonable estimates of actual evaporation when driven by observations at point-scales over multi-day and seasonal periods. This included periods when soil moisture was not a strong limitation and also under drought conditions. Variations in the spatial pattern of actual evaporation provided a useful indicator of drought across the Prairie region of Western Canada. The results contribute to a better understanding of the effects of spatial associations of key factors on evaporation estimates in a Prairie landscape. The methodology developed for distributing net radiation from assimilated visible and thermal images could potentially be used in regional scale modelling applications for improving evaporation estimates using point scale estimation techniques. The modelling algorithms applied to derive point estimates of evaporation from surface reference data may be useful for operational purposes that require estimates of actual evaporation and for characterizing drought.
183

Impervious Areas: Examining the Undermining Effects on Surface Water Quality

Young, De'Etra Jenra 2010 December 1900 (has links)
This study explored the relationship between increased proportions of imperviousness in a watershed on surface water quality and examined the effectiveness of using remote sensing to systematically and accurately determine impervious surfaces. A supervised maximum likelihood algorithm was used to classify the 2008 high resolution National Agriculture Imagery Program (NAIP) imagery into six classifications. A stratified random sampling scheme was conducted to complete an accuracy assessment of the classification. The overall accuracy was 85%, and the kappa coefficient was 0.80. Additionally, field sampling and chemical analysis techniques were used to examine the relationship between impervious surfaces and water quality in a rainfall simulation parking lot study. Results indicated that day since last rain event had the most significant effect on surface water quality. Furthermore, concrete produced higher dissolved organic carbon (DOC), dissolved organic nitrogen (DON), potassium and calcium in runoff concentrations than did asphalt. Finally, a pollutant loading application model was used to estimate pollutant loadings for three watersheds using two scenarios. Results indicated that national data may overestimate annual pollutant loads by approximately 700%. This study employed original techniques and methodology to combine the extraction of impervious surfaces, utilization of local rainfall runoff data and hydrological modeling to increase planners' and scientists' awareness of using local data and remote sensing data to employ predictive hydrological modeling.
184

Use GeoVRML¡BROAM Algorithm and Data Compression to Display 3D GIS

Sher, Chain-wei 12 February 2004 (has links)
Digital Earth is a kind of GIS application which use lots of computer techniques, including ¡§Computer Graphic¡¨, ¡§High quality Satellite Image¡¨, ¡§Multi-resolution¡¨, ¡¨ Metadata¡¨, ¡¨Level of detail¡¨, etc. In the past, geographers always tend to use triangle or grid structure to build 3D GIS. Now 3D GIS tend to use VRML to display virtual terrain data. Nevertheless, this display method is short of three-dimension analysis. It just uses 2.5 dimension to simulate 3 dimension space structure. This thesis is base on the theory of GeoVRML Quad-tree structure and use JAVA to implement ROAM algorithm. And this method can improve Quad-tree structure morphing error and raise virtual terrain display speed. This thesis use ETOPO5 5-minute DTM data to build Earth model (provide by NGDC) and Taiwan 40M DTM data, 200M, 100M, 50M, 25M satellite image to build Taiwan 3D GIS model. Meanwhile, this thesis addresses an unique three level structure to display 3D GIS model. One is Satellite Image layer, one is virtual terrain layer, and last one is 3D feature object.
185

A Study on XML-based Web GIS-Using a SVG System

Yang, Sheng-Bei 05 August 2003 (has links)
GIS (Geographic Information Systems) is gradually mature on the Internet, and the applications of the GIS, such as: living, entertainment, traffic, environment etc., are more extensive. People are very easy to get useful spatial information from Web GIS. SVG (Scalable Vector Graphics) was initiated by W3C (World Wide Web Consortium), it is an XML (eXtensible Markup Language)-based two-dimensional vector graphics standard on the internet. It is suitable to be used on the Web GIS. The research focuses on XML-based Web GIS including: spatial information and attribute data. The process to create a SVG system is discussed. Besides to write a software code for implementing a SVG system as a Web GIS, some functions were added to the system to promote the operating efficiency. Finally, two query applications were set up. One is Tapeng Bay to display fundamental setting up process and the other is Taipei school information query system to test the functions for SQL and statistical information. Keywords: Web GIS, XML, SVG, DOM
186

The long-term development of a watershed: spatial patterns, streamflow, and sustainability

DeFee, Buren Brooks, II 17 February 2005 (has links)
This study examines the relationship between the developing landscape and the water flowing through it. The study area was an 86 sq. mi. watershed located in the coastal plains in Harris County, Texas. Daily streamflow data for 52 years was obtained from USGS and coincident precipitation data was obtained from NOAA. Georeferenced parcel-level data was obtained from the Harris County Appraisal District with sufficient detail to determine year of development, parcel area, and impervious cover. Watershed boundaries were obtained from the Harris County Flood Control District. After controlling for daily precipitation, streamflow exhibited significant increases at all levels over time. Increasing streamflow was not associated with climate change. FRAGSTATS was used to quantify spatial patterns in the developed landscape on an annual basis. Regression analysis was used to determine the relationship between spatial and non-spatial measures of development and streamflow. It was found that models based on the spatial configuration of the developed landscape predict streamflow better than non-spatial measures such as total impervious cover. Several metrics were identified for their potential use as guidelines for urban planning.
187

Analyzing the connectivity potential of landscape geomorphic systems: a radar remote sensing and GIS approach, Estufa Canyon, Texas, USA

Ibrahim, ElSayed Ali Hermas 01 November 2005 (has links)
Connectivity is considered one of the fundamental aspects that influences the rate of mass movement in the landscape. The connectivity aspect has been acknowledged from various conceptual geomorphic frameworks. None of these provided a developmental methodology for studying the connectivity of geomorphic systems, especially at the scale of the fluvial system. The emphasis in this research is placed on defining variables of the geomorphic systems that influence the connectivity potential of these systems. The landscape gradient, which is extracted from the Digital Elevation Model (DEM), and the surface roughness, which is extracted from radar images, are used to analyze the connectivity potential of geomorphic systems in the landscape. Integration of these variables produces a connectivity potential index of the various geomorphic systems that compose the fluvial system. High values of the connectivity potential index indicate high potential of the geomorphic system to transport mass whereas the low values indicate low potential of the geomorphic system to transport mass in the landscape. Using the mean values of the connectivity potential index, the geomorphic systems in the landscape can be classified into geomorphic systems of low connectivity potential, geomorphic systems of intermediate connectivity potential and geomorphic systems of high connectivity potential. In addition to the determination of the relative connectivity potential of various geomorphic systems, the connectivity potential index is used to analyze the system-wide connectivity. The ratios between the connectivity potential index of the upstream geomorphic systems and the connectivity potential index of the downstream geomorphic systems define system-wide connectivity in the landscape. High ratios reflect the high potential of the upstream geomorphic systems to transport mass in the downstream direction. Low ratios indicate the influence of the downstream geomorphic systems in maximizing mass movement in the upstream geomorphic systems. The presence of high and low ratios suggests the presence of a high system-wide connectivity. As the ratio approaches unity, mass movement is minimized in the landscape indicating low system-wide connectivity. Applying the above approach to Estufa Canyon, Texas, illustrated that Estufa Canyon is a dynamic fluvial system with high system-wide connectivity.
188

Delineating wetlands using geographic information system and remote sensing technologies

Villeneuve, Julie 12 April 2006 (has links)
During the last century wetlands have considerably decreased. The principal cause is urbanization, especially in large urban regions such as the Houston area. In order to protect the remaining wetlands, they have to be monitored carefully. However monitoring wetland is a difficult and time-demanding task because it has to be done repetitively on large areas to be effective. This study was conducted to determine if Geographical Information System (GIS) and remote sensing technologies would allow accurate monitoring of wetland as a less time-consuming method. With this idea, a suitability model was developed to delineate wetlands in the Houston area. This model combined GIS and remote sensing technologies. The data used for this study were as high spatial resolution as possible and were generally easy to obtain. This suitability model consisted of four submodels: hydrology, soil, vegetation and multi- attribute. Each submodel generated a Wetland Suitability Index (WSI). Those WSI were summed to obtain a general WSI. The suitability model was calibrated using half of the study area. During calibration, the general model was evaluated as well as each individual index. Generally, the model showed a lack of sensitivity to changes. However, the model was slightly modified to improve the delineation of upland wet- lands by increasing the weight of the soil submodel. This model was validated using the second half of the study area. The validation results improved a bit compared to the calibration results; however they remained weak. It was demonstrated that the model does not favor riverine wetlands over upland wetlands, nor large size wetlands. The model ground truth data were evaluated and were suffciently proven to be up to date. Those results indicated that the weakness of the model must come from inac- curacy in the input data. Therefore, the study showed that while existing computing capacity supports remote delineation, spatial accuracy is still insuffcient to perform correct wetland delineation using remote sensing and GIS technologies.
189

Development of a geographical operating environment

Tomlinson, S. J. January 1998 (has links)
There have been many changes in Geographical Information Systems (GIS) technology which are beneficial for analysis and visualisation of Geographical Information (GI) but these have failed to be applied to non GIS users. The development of a computer based working environment for using GI within generic decision-making situations is a necessity if more use is to be made of GI by non GIS specialists. Problems are outlined for the incorporation of GI into existing systems : GIS and Spatial Decision Support Systems (SDSS). Issues of usability, integration of software/information and functionality have slowed the wider acceptance of GIS. 'These issues have lead to the development of a conceptual functional model of a Geographical Operating Environment (GOE). The GOE is proposed as a solution to the use of GI within a generic computer based decision-making environment for non GIS users. The GOE integrates the use of GI and non GI to allow the user to view and analyse information within a decision-making context. A series of prototypes have been developed and tested, mostly in conjunction with commercial organisations. The research has shown that there is much benefit in facilitating access to GI and non GI by decision-makers and that alternate strategies can be visualised and analysed. However, there are still problems for the mainstream use of GI within generic decision-making using existing computer systems from both a technological and sociological perspective. Decision-makers would benefit from the .additional analytical and visualisation techniques that can be applied to GI through the use of a GI based working environment such as the GOE.
190

Hur kan GIS införas i gymnasieskolan? : Exempel från Polhemsskolan i Gävle

Stigson, Jens January 2011 (has links)
GIS är inte längre en ny teknologi utan har funnits i snart fem decennier. Trots det har GIS inte hittat sin plats i den svenska gymnasieskolan, jämfört med t.ex. webb-design och andra datorteknikkurser som har funnits under en kortare tid. På den tekniska gymnasieutbildningen på Polhemsskolan i Gävle har GIS-utbildning bedrivits sedan 1999. De slutsatser som framkommer i rapporten är att en teknisk GIS-utbildning inte enbart är för elever på tekniska gymnasieutbildningar utan även för elever på andra gymnasieprogram eftersom de har samma förutsättningar att lära sig verktyget. Det konstateras även att det genom åren har funnits både nationella och internationella problem med att införa GIS-undervisning i gymnasieskolan. I rapporten finns förslag på hur problemen kan lösas. På Polhemsskolan i Gävle har det dock inte inneburit några större problem, mycket p.g.a. det stora stöd som har funnits tillgängligt. I rapportens slutdel finns även en uppföljning av vad som har hänt under de tolv år som har gått sedan GIS-utbildningen på Polhemsskolan i Gävle började. This study shows that a technical GIS education is not only for pupils at the technical education but also other pupils have the same possibilities to learn this tool. Furthermore there is a national and international problem to introduce GIS in the secondary school. There are propositions in this study on how to solve this problem. The introduction was not a major problem at Polhemsskolan in Gävle, because of the large support that has been available. The end of this study includes a twelve year follow-up since the GIS education at Polhemsskolan in Gävle started. / GIS is no longer a new technology since it has existed for almost five decades. Despite this, GIS has not found its place in the Swedish secondary school education, compared with i.e. Web design and other computer skill courses that have existed for a shorter time. At the technical secondary school education at Polhemsskolan, Gävle, GIS education has been taking place since 1999. This study shows that a technical GIS education is not only for pupils at the technical education but also other pupils have the same possibilities to learn this tool. Furthermore there is a national and international problem to introduce GIS in the secondary school. There are propositions in this study on how to solve this problem. The introduction was not a major problem at Polhemsskolan in Gävle, because of the large support that has been available. The end of this study includes a twelve year follow-up since the GIS education at Polhemsskolan in Gävle started.

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