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Dissertation Information for Robert Yoder

NAME:
- Robert Yoder

DEGREE:
- Ph.D.

DISCIPLINE:
- Library and Information Science

SCHOOL:
- SUNY, Albany (USA) (1999)

ADVISORS:
- James Mower

COMMITTEE MEMBERS:
- Peter Bloniarz
- Stephen Edwin DeLong

MPACT Status: Fully Complete

Title: Design considerations for implementing octree based 3-D GIS

Abstract: Interest in 3-D GIS has increased due to advances in information technology and the realization of the limitations of traditional 2-D GIS as a tool in understanding geoscientific structures and processes that are inherently three dimensional.

The primary goal of this dissertation is to identify and quantify octree-based GIS design issues, including octree representation and geoprocessing algorithm selection with emphasis on neighbor-finding techniques. The following geoprocessing functions were studied: volume computation, surface area computation, Boolean (set) intersection, and connected component labeling.

Results indicate that the pointer octree representation delivers faster running times for all functions except volume computation and set operations, and that pointer octrees are not necessarily larger than the corresponding linear octree for the same object.

A fast algorithm for neighbor tesseral address computation is developed, along with techniques for finding smaller neighbors for both linear and pointer-based octrees in the context of the connected component labeling problem. Two methods are contrasted for finding smaller neighbors. The first method is a "pruned" octree search that investigates only those sub-tree paths that can possibly contain the neighbor. The other method uses the UNION-FIND technique to avoid smaller neighbor searches. UNION-FIND assigns component labels to equivalence classes that logically join component regions together. Empirical and analytic methods are used to study neighbor-finding for pointer and linear octrees.

Another octree representation called Breadth-First (BF) expressions is discussed, and a formula is developed to directly compute the offset for a node within a BF expression given its tesseral address. BF expressions are shown to have node search characteristics faster than linear octrees but slower than pointer octrees. BF expressions had greater storage requirements than both pointer and linear octrees as implemented for this dissertation.

Other results include a literature review and discussion of octree theory in a GIS context. A way to extend the UNION-FIND connected component label algorithm to support distributed computation is proposed.

MPACT Scores for Robert Yoder

A = 0
C = 0
A+C = 0
T = 0
G = 0
W = 0
TD = 0
TA = 0
calculated 2008-01-31 06:13:20

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