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An Improved Algorithmic Approach to Iterative Floodway Modeling using HECRAS and GISSelvanathan, Sivasankkar 07 January 2010 (has links)
Hydrologic Engineering Center's River Analysis System (HEC-RAS) software is commonly used to perform hydraulic analysis for floodplain delineation studies. In addition to floodplains, the hydraulic analysis also includes modeling a floodway in detailed floodplain study areas. Floodway modeling is an iterative process in which the 1% annual chance flood discharge is restricted within a floodway without exceeding a designated increase, called the surcharge (usually 1 foot), in water surface elevation. An engineer models flows along a reach to meet Federal Emergency Management Agency's (FEMA) surcharge requirements.
We present a tightly coupled system comprising of a commercial GIS (ArcGIS) and HECRAS that automates HECRAS's floodway encroachments modeling. The coupled system takes an automated approach, in which an initial floodway is developed by running HEC-RAS in an iterative fashion with minimal user intervention. A customized ArcGIS visual environment has been developed to edit, remodel, spatially analyze and map floodway boundaries. Four different encroachments fine-tuning options are provided which eliminates the need for a modeler to switch between HECRAS and GIS in the floodway modeling process. Thus, the tool increases the productivity of a modeler by cutting down on manual modeling time during floodway iterations and transition between HECRAS and ArcGIS. The transfer of HECRAS model output into the ArcGIS environment facilitates quick and efficient spatial analysis.
The final step in the floodway modeling process is to develop a smooth floodway boundary that can be mapped on a DFIRM. We have developed automated mapping algorithms that accomplish this task. Some manual fine-tuning is required to finalize the floodway to be printed on FEMA's Flood Insurance Rate Maps (FIRMs). / Ph. D.
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Evaluating time-series smoothing algorithms for multi-temporal land cover classificationWheeler, Brandon Myles 23 July 2015 (has links)
In this study we applied the asymmetric Gaussian, double-logistic, and Savitzky-Golay filters to MODIS time-series NDVI data to compare the capability of smoothing algorithms in noise reduction for improving land cover classification in the Great Lakes Basin, and providing groundwork to support cyanobacteria and cyanotoxin monitoring efforts. We used inter-class separability and intra-class variability, at varying levels of pixel homogeneity, to evaluate the effectiveness of three smoothing algorithms. Based on these initial tests, the algorithm which returned the best results was used to analyze how image stratification by ecoregion can affect filter performance.
MODIS 16-day 250m NDVI imagery of the Great Lakes Basin from 2001-2013 were used in conjunction with National Land Cover Database (NLCD) 2006 and 2011 data, and Cropland Data Layers (CDL) from 2008 to 2013 to conduct these evaluations. Inter-class separability was measured by Jeffries-Matusita (JM) distances between selected land cover classes (both general classes and specific crops), and intra-class variability was measured by calculating simple Euclidean distance for samples within a land cover class. Within the study area, it was found that the application of a smoothing algorithm can significantly reduce image noise, improving both inter-class separability and intra-class variability when compared to the raw data. Of the three filters examined, the asymmetric Gaussian filter consistently returned the highest values of interclass separability, while all three filters performed very similarly for within-class variability. The ecoregion analysis based on the asymmetric Gaussian dataset indicated that the scale of study area can heavily impact within-class separability. The criteria we established have potential for furthering our understanding of the strengths and weaknesses of different smoothing algorithms, thereby improving pre-processing decisions for land cover classification using time-series data. / Master of Science
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Aspects of bivariate time seriesSeeletse, Solly Matshonisa 11 1900 (has links)
Exponential smoothing algorithms are very attractive for the practical world
such as in industry. When considering bivariate exponential smoothing
methods, in addition to the properties of univariate methods, additional
properties give insight to relationships between the two components of a
process, and also to the overall structure of the model.
It is important to study these properties, but even with the merits the
bivariate exponential smoothing algorithms have, exponential smoothing
algorithms are nonstatistical/nonstochastic and to study the properties within
exponential smoothing may be worthless.
As an alternative approach, the (bivariate) ARIMA and the structural models
which are classes of statistical models, are shown to generalize the exponential
smoothing algorithms. We study these properties within these classes as they
will have implications on exponential smoothing algorithms.
Forecast properties are studied using the state space model and the Kalman
filter. Comparison of ARIMA and structural model completes the study. / Mathematical Sciences / M. Sc. (Statistics)
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Aspects of bivariate time seriesSeeletse, Solly Matshonisa 11 1900 (has links)
Exponential smoothing algorithms are very attractive for the practical world
such as in industry. When considering bivariate exponential smoothing
methods, in addition to the properties of univariate methods, additional
properties give insight to relationships between the two components of a
process, and also to the overall structure of the model.
It is important to study these properties, but even with the merits the
bivariate exponential smoothing algorithms have, exponential smoothing
algorithms are nonstatistical/nonstochastic and to study the properties within
exponential smoothing may be worthless.
As an alternative approach, the (bivariate) ARIMA and the structural models
which are classes of statistical models, are shown to generalize the exponential
smoothing algorithms. We study these properties within these classes as they
will have implications on exponential smoothing algorithms.
Forecast properties are studied using the state space model and the Kalman
filter. Comparison of ARIMA and structural model completes the study. / Mathematical Sciences / M. Sc. (Statistics)
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Smoothing for ZUPT-aided INSsSimón Colomar, David, Nilsson, John-Olof, Händel, Peter January 2012 (has links)
Due to the recursive and integrative nature of zero-velocity-update-aided (ZUPT-aided) inertial navigation systems (INSs), the error covariance increases throughout each ZUPT-less period followed by a drastic decrease and large state estimate corrections as soon as ZUPTs are applied. For dead-reckoning with foot-mounted inertial sensors, this gives undesirable discontinuities in the estimated trajectory at the end of each step. However, for many applications, some degree of lag can be tolerated and the information provided by the ZUPTs at the end of a step can be made available throughout the step, eliminating the discontinuities. For this purpose, we propose a smoothing algorithm for ZUPT-aided INSs. For near real-time applications, smoothing is applied to the data in a step-wise manner requiring a suggested varying-lag segmentation rule. For complete off-line processing, full data set smoothing is examined. Finally, the consequences and impact of smoothing are analyzed and quantified based on real-data. / <p>QC 20130114</p>
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