WorldCat Identities

Saalfeld, Alan

Works: 24 works in 30 publications in 1 language and 38 library holdings
Genres: Academic theses  Mathematical formulae  Census data 
Roles: Author
Classifications: QA76.M3,
Publication Timeline
Most widely held works about Alan Saalfeld
Most widely held works by Alan Saalfeld
Conflation : automated map compilation by Alan Saalfeld( Book )

3 editions published between 1987 and 1993 in English and held by 5 WorldCat member libraries worldwide

Abstract: "Map conflation is the compilation or reconciliation of two variants of a map of the same region. The theory and practice of automated map conflation evolved from a pilot project at the United States Bureau of the Census from 1983 through 1985. During that project, a prototype system was designed and built for automated map conflation of a large collection of pairs of digital cartographic files of major metropolitan areas in the United States. Although the project focused on matching and merging specific concrete cartographic data sets, it engendered a collection of computer science techniques and mathematical generalizations that have since become interesting in their own right. A map conflation system requires efficient and robust combinatorial, numerical, and geometric algorithms to implement a rather broad spectrum of mathematical theories. This dissertation provides a broad mathematical context for map conflation, a collection of algorithms and tools for building a map conflation system, an analysis of the performance of those algorithms, an assessment of overall performance of systems that were built following a simple paradigm, and a brief discussion of other areas of automated cartography and spatial data handling that could benefit from lessons learned in developing the conflation system."
Dynamic maintenance of Delaunay triangulations by Thomas C Kao( Book )

1 edition published in 1991 in English and held by 4 WorldCat member libraries worldwide

Randomized methods: For triangulation building or updates involving large collections of point, randomized techniques are employed to improve the expected performance of the algorithm, irrespective of the distribution of points. Persistence: Earlier versions of the triangulation can be recovered efficiently."
Analytical conflation of spatial data from municipal and federal government agencies by Hoseok Kang( )

2 editions published in 2002 in English and held by 3 WorldCat member libraries worldwide

We present two different map models corresponding to two different mathematical approaches to map conflation. The first model is based on the cell model of map in which a map is a cell complex consisting of 0-cells, 1-cells, and 2-cells. The second map model is based on a different set of primitive objects that remain homeomorphic even when generalized. The second model facilitates map conflation by guaranteeing the existence of both local and global homeomorphisms everywhere. Matching operations in map conflation are defined in one of two ways, depending on the map model used. The second model allows for the possibility of non-homeomorphic matching. The first model does not. If corresponding matching features within a subregion happen to have the same dimension and be homeomorphic, then more conventional matching strategies may be applied. If corresponding features, however, are not homeomorphic, then an operation called topological surgery may be implemented. A 0-cell conflation test is proposed to deal with the non-homeomorphic case. A new hierarchical based map conflation is also presented to be applied to physical, logical, and mathematical boundaries and to reduce the complexity and computational load. Map conflation techniques developed explicitly for Census maps are formulated and implemented. These new methods guarantee producing a conflated result that is topologically consistent with reference maps. This dissertation also describes how national maps could be updated effectively by exchange of map information between federal and local governments
A Database System as a Tool for Comparing, Updating, and Conflating Spatial Data From DLG and GPSVan by Kosta Bidoshi( Book )

2 editions published in 1995 in English and held by 2 WorldCat member libraries worldwide

A one pass line-following algorithm for linear feature extraction by Zhiyuan Zhao( Book )

2 editions published in 1997 in English and held by 2 WorldCat member libraries worldwide

This paper presents a new algorithm for converting raster-scanned maps to vector format. By exploiting local geometric symmetries of multi-pixel-width line features in raster format, the algorithm follows the center of a line feature by maintaining an equal distance to the exterior of the feature in the two directions perpendicular to the current moving direction. The algorithm generates vector data for this feature without thinning. Three goals are achieved by the algorithm: (1) it is suitable for general line features such as single lines, double lines (e.g. roads), irregular double lines (rivers), and non-continuous lines of any pattern (streams, railroads); (2) it can ignore most common noise found in scanned raster data; (3) it has high speed performance (running in time linearly proportional to the number of interior black pixels). The algorithm is implemented in the Line-Following Tool (LiFT) of the GISOM project (Generating Information from Scanning Ohio Maps) at the Ohio State University Center for Mapping. The algorithm is applied to general images by using more general measurement 'energy' to maintain the symmetric property of the center line of line feature from image
A thorough investigation of digital terrain model generalization using adaptive filtering by Gabor Terei( )

1 edition published in 1999 in English and held by 2 WorldCat member libraries worldwide

The amount of available data in a Geographical Information System (GIS) is growing at a very high rate. Many of the data sets are at different scales, requiring cross-referencing and integration. Real-time data processing and display capabilities of such systems are also at an all-time high, making generalization a feasible and necessary concept for interactive and automated procedures. Digital Terrain Models (DTM) are now a significant component of GIS, thus requiring generalization. An extensive literature review of DTMs from basic definitions and conceptual frameworks to available algorithms for generalization and different applications shows that there is no complete solution at the moment due to the lack of analytical theory underlying the generalization procedures. This research explores the possibilities of combining theory with practice, that is combining the generalization of the underlying structure (SLM) and other terrain structures with the heuristic methods used to generate visually pleasing views using selective filtering. An algorithm based on the Constrained Delaunay Triangulation has been developed and thoroughly tested, using visual analysis and statistical measures. The results proved that the unification of model generalization and statistical generalization is both feasible and desirable. Several methods for comparing the outcome of generalization procedures have been developed, allowing an objective insight into the underlying structure of the terrain and theoretical aspects that lead to a better understanding to automated generalization procedures
New methods for spatial statistics in geographic information systems by Yaron A Felus( )

1 edition published in 2001 in English and held by 2 WorldCat member libraries worldwide

This thesis is concerned with the development of new methods to implement advanced spatial statistics procedures within Geographic Information Systems. Two approaches are investigated; the first uses Delaunay triangulation data structure to select an appropriate subset of the data and perform Ordinary Kriging interpolation. The second studies an advanced spatial statistics procedure, the optimal biased kriging, which is more efficient in terms of the Mean Squared Prediction Error
A Modified Douglas-Peucker simplification algorithm : a consistent displacement line simplification by Yanyan Zhang( )

2 editions published in 1996 in English and held by 2 WorldCat member libraries worldwide

Displacement consistency has remained a challenging problem in line simplification. Though it is often considered the best line simplification algorithm, the Douglas-Peucker algorithm, however, like most line simplification algorithms, does not take into account displacement consistency. Assume there is a chain c with n vertices, a point set P with m points scattering along the two sides of c and also there are other chains lying beside chain c. A line simplification algorithm is said to have displacement consistency for c only if each of the points in P and each of the vertices in other chains remains on the same side of the simplified c after applying the algorithm. n this thesis, the Douglas-Peucker algorithm is modified to achieve displacement consistency. The key point of the modification is: checking will be done for all the points and vertices that will potentially interfere with the simplified chain before each vertex elimination, and guarantee simplification only happens when it is safe. There are two method given for choosing "characteristic" vertex after encountering unsafe points
Surface velocities of the East Antarctic Ice Streams from radarsat-1 interferometric synthetic aperture radar data by Zhiyuan Zhao( )

1 edition published in 2001 in English and held by 2 WorldCat member libraries worldwide

The newly discovered East Antarctic Ice Streams drain a significant portion of the Antarctic Ice Sheet. Therefore, changes in their flow behavior can significantly alter ice-sheet mass-balance and influence global sea level. This dissertation research created the most comprehensive measurements to date of surface velocity across the East Antarctic Ice Streams using RADARSAT-1 interferometric synthetic aperture radar (InSAR) data acquired in 1997. Two-dimensional surface velocity was derived by combined interferometric and speckle matching techniques. Improvements in both techniques mediated some of the unique problems and limitations associated with imaging the Antarctic Ice Sheet using RADARSAT-1. The improvements included Delaunay triangulation based co-registration of SAR images, phase reconciliation of disconnected phase patches, and two-dimensional velocity calibration using extended velocity control points. The research produced a highly dense, highly accurate, two-dimensional surface velocity map of the East Antarctic Ice Streams, and a by-product coherence map reflecting surface changes. The velocity uncertainty is better than 15 m/year and velocity direction error is within 5? on the ice shelf and ice streams. Ice-stream shear-margins were mapped and the comparison between the ice stream margins and BEDMAP subglacial topography suggests that ice stream flow is controlled by bedrock topography. Mass balance calculations indicate that the ice stream and Filchner Ice Shelf system is not significantly thinning or thickening. There is evidence to suggest that at least one of the individual ice streams (Bailey Glacier) is thickening at a rate of 0.25? 0.06 m/year. Ice stream surfaces are generally convex and Slessor Glacier and Bailey Ice Stream driving stresses are large compared to the concave shaped West Antarctic Ice Streams. The surface topography of Recovery Glacier varies the most from an equilibrium profile and stretches of the Recovery Glacier have low driving stress, suggestive of flow on a lubricated bed. The convexity of the surface profiles, high driving stress, evidence of streaming flow and the shape of the glacier bed suggest that a change in ice stream dynamics could potentially result in an imbalanced discharge of large amounts of ice into the sea. Title from first page of PDF file
Canonical cyclic orderings of point sets in the plane by Alan Saalfeld( )

1 edition published in 1990 in English and held by 1 WorldCat member library worldwide

For points in general position in the plane, we describe a family of cyclic orderings which are invariant under isometries. We prove that the family can contain at most 60 orderings. The entire family of orderings can be built in O(nlog n) time in O(n) space, where n is the number of points to be ordered. The method used to generate the cyclic orderings of points works for the vertex set of any free tree em- bedded in the plane. We apply the method to the Euclidean minimum spanning tree for the points in general position to obtain our family of cyclic orderings
Classifying and comparing spatial relations of computerized maps for feature matching applications by Alan Saalfeld( Book )

1 edition published in 1987 in English and held by 1 WorldCat member library worldwide

Modern computerized maps either contain digital information on spatial relations, such as adjacency relations, shape, network patterns, and measures of position and distance of features, or they permit derivation of that information from the feature data that they do contain
The combinatorial complexity of polygon overlay by Alan Saalfeld( Book )

1 edition published in 1989 in English and held by 1 WorldCat member library worldwide

The number of elementary connected regions arising from polygon overlay of two or more map layers is an important value to have in planning for da.ta and in making processing time estimates for overlay applications. That number may be computed directly from the line graphs of the two (or more) layers and from the intersection graph(s) of those line graphs. A formula for that computation is derived using tools of algebraic and combinatorial topology which relate the connectivity of a union of sets to the connectivity of the sets themselves and their intersection
A gps/gis real time curve warning system by Huiyu Wang( )

1 edition published in 1996 in English and held by 1 WorldCat member library worldwide

Storing, retrieving and maintaining information on geographic structures : a geographic tabulation unit base (GTUB) approach by David Meixler( )

1 edition published in 1986 in English and held by 1 WorldCat member library worldwide

Triangulated data structures for map merging and other applications in geographic information systems by Alan Saalfeld( )

1 edition published in 1987 in English and held by 1 WorldCat member library worldwide

Statistical analysis of map differences by Alan Saalfeld( Book )

1 edition published in 1987 in English and held by 1 WorldCat member library worldwide

Digital map data lends itself to computerized statistical analysis much like any other computer-readable data file. Comparative data analysis is possible when two files are present and linkages can be established between some of the feature records of the two files
Minimizing map distortion using oblique projections by Boju Zhang( )

1 edition published in 2017 in English and held by 1 WorldCat member library worldwide

We provide a precise mathematical definition of map distortion, and we introduce several map projections that have minimal distortion for certain specific regions of the Earth (namely, regions whose boundary consists of one or two parallels of latitude). The minimizing projections for these regions will all have normal aspect. We show that oblique aspect projections have the same distortion properties as their normal aspect counterparts on earth regions bounded by one lesser circle or by two lesser circles lying in parallel planes. We summarize the good consequences of having small distortion, and we outline a strategy for finding the best oblique map projection of least distortion for any region on the Earth. We then implement that strategy to find projections of least distortion for some unusually shaped countries, states and other regions
It doesn't make me nearly as cross : some advantages of the point-vector representative by Alan Saalfeld( Book )

1 edition published in 1987 in English and held by 1 WorldCat member library worldwide

The point-vector representation for line segments offers several advantages over other more familiar representations for lines and line segments, such as the point-slope form, the slope-intercept form and the two-point form. With the point-vector form, line segment intersection routines and related cartographic computations, such as a point-in-polygon routines and detection of near intersections, can be steamlined, simplified, and more easily understood
Exploration of the potential for hydrologic monitoring via passive microwave remote sensing with a new footprint-based algorithm by Dongyue Li( )

1 edition published in 2011 in English and held by 1 WorldCat member library worldwide

Snow is an important component of hydrology and climate at both local and global scales. In-situ snowpack measurements provide accurate, reliable data on snowpack properties, but represent only a point measurement of the spatially variable snow cover, lacking spatial continuity. Spaceborne passive microwave remote sensing (PM) measurements are attractive for snowpack characterization due to their continuous global coverage, but a drawback of coarse spatial resolution. In this paper, a footprint based method is developed to improve the PM snow measurements by extracting more information on snow properties. Several experiments carried out in Kern River Basin, Sierra Nevada, USA show PM data processed via the new method contain significant snowpack information, especially information on snow water equivalent (SWE) and melt timing, which are two most important snow properties. When compared with the traditionally used PM dataset, the newly processed data show three times more sensitivity to in-situ SWE, and a 9.6% increase in the correlation coefficient between SWE and PM measurements: both indicate the new data processing method has the capability to improve the PM data's sensitivity to snow
Classification of man-made urban structures from lidar point clouds with applications to extrusion-based 3-D city models by Anita Thomas( )

1 edition published in 2015 in English and held by 1 WorldCat member library worldwide

Three dimensional city models are vital to a wide range of applications, including transportation, urban planning, emergency preparedness, virtual tourism, and gaming. Extrusion is among the most straightforward methods of achieving a 3-D city model. Extrusion vertically stretches a 2-D structure polygon into a 3-D structure by extending the entire polygon to one common height. A lack of details, such as rooftop slope and structural hollowness, however, render the method too generic for use in many applications. My algorithm is aimed at preserving these details. This paper proposes the use of lidar point clouds to detect and classify manmade urban structures in preparation for informed point-based extrusion - which vertically stretches each point to its individual height rather than stretching all points that comprise a given structure to one height - and for the incorporation of hollowness into structures classified as bus or bike shelters, scaffolding, or bridges. These modifications will capture surface details as well as correctly display hollowness, thus increasing the usefulness of extrusion for 3-D city modeling. While inaccuracy in both the clustering of points that comprise some structures and the identification of some structures' border points negatively impacts subsequent processes, this algorithm can still correctly classify up to 76% of a given study area. Revisions proposed in this paper will likely increase this accuracy
moreShow More Titles
fewerShow Fewer Titles
Audience Level
Audience Level
  General Special  
Audience level: 0.00 (from 0.00 for Conflation ... to 0.00 for Conflation ...)

Alternative Names
Saalfeld, Alan John

English (27)