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Group: GeoTools - library 34 articles

A Simple and Eﬃcient Algorithm for High-Quality Line Labeling

[CiTO]
In GIS and GeoComputation (2000)
posted to by ianturton to the group GeoTools on 2010-09-17 18:19:51

✔ A Coordinate System for Hexagonal Pixels

[CiTO]
In PROC. SPIE! THE INTERNATIONAL SOCIETY FOR OPTICAL ENGINEERING, Vol. 3661 (1999), pp. 1-2, doi:10.1.1.10.7937
posted to by mbedward to the group GeoTools on 2010-06-04 07:51:16

Abstract

A coordinate system is described which provides a natural means for representing hexagonally-organized pixels. The coordinate system has the unusual property that its basis vectors are not orthogonal. Vector-space properties and operations are described in this coordinate system, and shown to be straightforward computations. Some image processing algorithms, including calculations of image gradients and variable-conductance diffusion, are expressed and analyzed. ...

Note (first note only)

This is relevant to the GeoTools vector grid module (gt-grid) which can create hexagonal grids

✔ An iterative algorithm to compute geodetic coordinates

[CiTO]
Computers & Geosciences (05 May 2010), doi:10.1016/j.cageo.2010.02.004
posted to by ianturton to the group GeoTools on 2010-05-11 21:01:59

Abstract

By using the Newton-Raphson method to solve a quartic equation of the Lagrange parameter, we propose a new iterative algorithm for the transformation from Cartesian to geodetic coordinates. Numerical experiments show that the new method is sufficiently precise and free from singularity and non-convergency, except within 50 km of the geocentre. After one iteration, the maximum error of latitude is less than 10 -8 arc-seconds and the relative height error is less than 10 -15 over the range of geodetic heights from ...

✔ Efficient triangulation of simple polygons

[CiTO]
The Visual Computer, Vol. 7, No. 5. (1 September 1991), pp. 280-295, doi:10.1007/bf01905693
posted to by ianturton to the group GeoTools on 2010-04-23 19:41:57

Abstract

This paper considers the topic of efficiently traingulating a simple polygon with emphasis on practical and easy-to-implement algorithms. It also describes a newadaptive algorithm for triangulating a simplen-sided polygon. The algorithm runs in timeO(n(1+to)) witht0n. The quantityt0 measures theshape-complexity of thetriangulation delivered by the algorithm. More preciselyt0 is the number of obtained triangles contained in the triangulation that share zero edges with the input polygon and is, furthermore, related to the shape-complexity of theinput polygon. Although the worst-case complexity of the ...

✔ Nearest Neighbor Queries

[CiTO]
(1995), pp. 71-79
posted to by ianturton to the group GeoTools on 2010-01-31 19:06:58

Abstract

A frequently encountered type of query in Geographic Information Systems is to find the k nearest neighbor objects to a given point in space. Processing such queries requires substantially different search algorithms than those for location or range queries. In this paper we present an efficient branch-and-bound R-tree traversal algorithm to find the nearest neighbor object to a point, and then generalize it to finding the k nearest neighbors. We also discuss metrics for an optimistic and a pessimistic search ordering ...

[CiTO]
In South African Institute of Computer Scientists and Information Technologists Annual Conference (September 2001)
posted to by ianturton to the group GeoTools on 2010-01-28 16:49:01

Abstract

Two polygons are adjacent if they have edges which share a common edge segment. In this paper we consider the problem of ﬁnding adjacencies in a set of n non-overlapping polygons. Using the fact that adjacent edges must lie on the same line, an algorithm with time complexity Θ(z log z) (where z is the total number of edges) is derived. Thereafter, we consider the particular case where the polygons are convex, as this has practical applications. Using the properties of convex polygons, we derive ...

✔ Escaping RGBland: Selecting colors for statistical graphics

[CiTO]
Computational Statistics & Data Analysis, Vol. 53, No. 9. (01 July 2009), pp. 3259-3270, doi:10.1016/j.csda.2008.11.033
posted to by ianturton to the group GeoTools on 2010-01-08 15:39:19 along with 5 people

Abstract

Statistical graphics are often augmented by the use of color coding information contained in some variable. When this involves the shading of areas (and not only points or lines)—e.g., as in bar plots, pie charts, mosaic displays or heatmaps—it is important that the colors are perceptually based and do not introduce optical illusions or systematic bias. Based on the perceptually-based Hue-Chroma-Luminance (HCL) color space suitable color palettes are derived for coding categorical data (qualitative palettes) and numerical variables (sequential and diverging palettes). ...

✔ Unfolding the Earth: Myriahedral Projections

[CiTO]
Cartographic Journal, The, Vol. 45, No. 1. (February 2008), pp. 32-42, doi:10.1179/000870408x276594
posted to by mbedward to the group GeoTools on 2009-12-11 02:49:35 along with 1 person

Abstract

Myriahedral projections are a new class of methods for mapping the earth. The globe is projected on a myriahedron, a polyhedron with a very large number of faces. Next, this polyhedron is cut open and unfolded. The resulting maps have a large number of interrupts, but are (almost) conformal and conserve areas. A general approach is presented to decide where to cut the globe, followed by three different types of solution. These follow from the use of meshes based on the ...

Note (first note only)

The full text of the article is freely available from the IngentaConnect link above

Photo Repair and 3D Structure from Flatbed Scanners

[CiTO]
In VISAPP 2009 - International Conference on Computer Vision Theory and Applications, Lisbon, Portugal, Feb 5-9, 2009 (2009)
posted to no-tag by mbedward to the group GeoTools on 2009-08-13 11:15:14

Abstract

We introduce a technique that allows 3D information to be captured from a conventional flatbed scanner. The technique requires no hardware modification and allows untrained users to easily capture 3D datasets. Once captured, these datasets can be used for interactive relighting and enhancement of surface detail on physical objects. We have also found that the method can be used to scan and repair damaged photographs. Since the only 3D structure on these photographs will typically be surface tears and creases, our ...

Note (first note only)

Includes some interesting image processing algorithms that are relevant to geo-spatial applications

Modelling Spatial Relations by Generalized Proximity Matrices

[CiTO]
In V Brazilian Symposium in Geoinformatics, GeoInfo 2003, Campos do Jordão, 2003 (2003)
posted to by mbedward to the group GeoTools on 2009-07-08 09:10:23

Towards a generalized map algebra: principles and data types

[CiTO]
In VI Brazilian Symposium in Geoinformatics, GeoInfo 2005, Campos do Jordão 2005 (2005)
posted to by mbedward to the group GeoTools on 2009-07-08 08:40:56

✔ Building GML-native web-based geographic information systems

[CiTO]
Computers & Geosciences (04 May 2009), doi:10.1016/j.cageo.2008.11.009
posted to by ianturton to the group GeoTools on 2009-06-25 21:40:04 along with 1 group

Abstract

Disaster response systems are designed to facilitate decision-making based on large amounts of heterogeneous geographic information. Most geographic information systems (GISs) use relational databases to manipulate information efficiently. However, they suffer from interoperability issues because they need to expend significant effort mapping heterogeneous geographic information, which may have complicated structures, into relational data models, and vice versa. Geography Markup Language (GML) is regarded as a standard for expressing, storing, and exchanging geospatial data, and has been applied to help solve interoperability ...

✔ Variable-scale representation of road networks on small mobile devices

[CiTO]
Computers & Geosciences (09 May 2009), doi:10.1016/j.cageo.2008.12.009
posted to by ianturton to the group GeoTools on 2009-06-25 21:38:01 along with 1 group

Abstract

A method is proposed for the adaptive multi-scale representation of road networks for location-based service applications. The method is able to automatically set a feasible scale according to geographic scope, the complexity of the road network, and the distance to the viewer. Moreover, the method achieves multi-scale representations of road networks on a display screen. The key steps of the method and the initial experimental studies undertaken to evaluate its feasibility are described. ...

✔ A new hierarchical triangle-based point-in-polygon data structure

[CiTO]
Computers & Geosciences (24 April 2009), doi:10.1016/j.cageo.2008.09.013
posted to by ianturton to the group GeoTools on 2009-06-05 22:08:06

Abstract

The point-in-polygon or containment test is fundamental in computational geometry and is applied intensively in geographical information systems. When this test is repeated several times with the same polygon a data structure is necessary in order to reduce the linear time needed to obtain an inclusion result. In the literature different approaches, like grids or quadtrees, have been proposed for reducing the complexity of these algorithms. We propose a new data structure based on hierarchical subdivisions by means of tri-cones, which ...

✔ Efficient cartogram generation: a comparison

[CiTO]
Information Visualization, IEEE Symposium on In IEEE Symposium on Information Visualization, 2002. INFOVIS 2002., Vol. 0 (2002), pp. 33-36, doi:10.1109/infvis.2002.1173144
posted to by ianturton to the group GeoTools on 2009-05-13 22:16:20 along with 3 people and 2 groups

Abstract

Cartograms are a well-known technique for showing geography-related statistical information, such as population demographics and epidemiological data. The basic idea is to distort a map by resizing its regions according to a statistical parameter, but in a way that keeps the map recognizable. We deal with the problem of making continuous cartograms that strictly retain the topology of the input mesh. We compare two algorithms to solve the continuous cartogram problem. The first one uses an iterative relocation of the vertices ...

✔ 2-level r-tree index based on spatial grids and Hilbert R-tree

[CiTO]
Geo-Spatial Information Science, Vol. 9, No. 2. (9 June 2006), pp. 135-141, doi:10.1007/bf02826939
posted to by mbedward to the group GeoTools on 2009-05-12 05:15:25 along with 1 person

Abstract

Abstract  Multi-level spatial index techniques are always used in large spatial databases. After a general survey of R-tree relevant techniques, this paper presents a novel 2-level index structure, which is based on the schemas of spatial grids, Hilbert R-tree and common R-tree. This structure is named H2R-tree, and it is specifically suitable for the indexing highly skewed, distributed, and large spatial database. Algorithms and a sample are given subsequently. ...

✔ A raster-based technique for analysing habitat configuration: The cost-benefit approach

[CiTO]
Ecological Modelling, Vol. 202, No. 3-4. (10 April 2007), pp. 324-332, doi:10.1016/j.ecolmodel.2006.10.016
posted to by mbedward to the group GeoTools on 2009-05-11 14:59:18 along with 1 person

Abstract

Advances continue to be made in modelling the spatial pattern of habitat. However, for models to be come more useful spatial pattern needs to be integrated with dynamic ecological processes. Existing modelling techniques often struggle to integrate faunal movement abilities or are impractical for routine application. We present here the cost-benefit approach (CBA), a modelling approach that integrates the costs of movement to organisms with the benefits of access to habitat. The approach brings together landscape ecology's interest in realistically complex ...

Note (first note only)

Includes a brief description of a simplifying algorithm for neighbourhood calculations in a raster. This algorithm involves defining 'petals': aggregations of cells with size increasing with distance from the target cell.

The Relative Effectiveness of Some Common Graduated Point Symbols in the Presentation of Quantitive Data.

[CiTO]
In Symposium on the Influence of the Map User on Map Design (1971)
posted to by ianturton to the group GeoTools on 2009-05-08 18:15:17

Abstract

Some general philosophy about maps is presented in the introduction. It is noted that the main purpose of a map is to generate an intellectual response through visual symbols. Quantitative distribution maps present a number of design problems that have led to continuing investigations of graduated circles as point symbols. A summary of the original graduated circle study, by the author, is presented. Six advantages to using graduated circles are summarized, however, map users consistently underestimate size differences when relying on ...

✔ OGC Catalog Services: a key element for the development of Spatial Data Infrastructures

[CiTO]
Computers & Geosciences In Geospatial Research in Europe: AGILE 2003, Vol. 31, No. 2. (March 2005), pp. 199-209, doi:10.1016/j.cageo.2004.05.015
posted to by ianturton to the group GeoTools on 2009-04-20 23:26:15 along with 2 people and 1 group

Abstract

One of the essential components for the construction of a geographic spatial data infrastructure at a regional, national or global level is the geographic information catalog server. But, for the catalog to be a useful component, it must enable access to geographic information metadata independently of the nature of search client applications, in other words, client applications do not need to be developed by the same company or same technology that implemented the server. In this sense, the contribution of the ...

Building boundary extraction based on LIDAR point clouds data

[CiTO]
In ISPRS Congress Beijing 2008, Proceedings of Commission III (2008)
posted to by mbedward to the group GeoTools on 2009-04-06 03:33:58

Abstract

LIDAR (Light Detection And Ranging) is an active remote sensing system, which could provide fleetly three dimensional information of earth surface with high vertical accuracy. Now the building boundary extraction and normalization is the key approach for 3D modeling of building and city mapping. In this paper, a new algorithm named Alpha Shapes is developed to extract the building boundary. Compared with other algorithms, Alpha Shapes algorithm works effectively in inner and outer boundaries extraction from point clouds data with convex ...

Note (first note only)

The author presents a very simple concave hull algorithm based on alpha-shapes.

✔ Color image segmentation: advances and prospects

[CiTO]
Pattern Recognition, Vol. 34, No. 12. (December 2001), pp. 2259-2281, doi:10.1016/s0031-3203(00)00149-7
posted to by mbedward to the group GeoTools on 2009-03-31 11:55:08 along with 4 people

Abstract

Image segmentation is very essential and critical to image processing and pattern recognition. This survey provides a summary of color image segmentation techniques available now. Basically, color segmentation approaches are based on monochrome segmentation approaches operating in different color spaces. Therefore, we first discuss the major segmentation approaches for segmenting monochrome images: histogram thresholding, characteristic feature clustering, edge detection, region-based methods, fuzzy techniques, neural networks, etc.; then review some major color representation methods and their advantages/disadvantages; finally summarize the color image ...

✔ Developing local measures of spatial association for categorical data

[CiTO]
Journal of Geographical Systems, Vol. 5, No. 2. (1 August 2003), pp. 139-160, doi:10.1007/s10109-003-0110-3
posted to by mbedward to the group GeoTools on 2009-03-31 11:37:20

Abstract

This paper describes a procedure for extending local statistics to categorical spatial data. The approach is based on the notion that there are two fundamental characteristics of categorical spatial data; composition and configuration. Further, it is argued that, when considered locally, the latter should be measured conditionally with respect to the former. These ideas are developed for binary, gridded data. Local composition is measured by counting the numbers of cells of a particular type, while local configuration is measured by join ...

Analysing spatial point patterns in 'R'

[CiTO]
posted to by mbedward to the group GeoTools on 2009-03-27 00:40:08

Abstract

These workshop notes, written in 2008, cover statistical methods available in public domain software. The workshop uses the statistical package 'R' and is based on 'spatstat', an add-on library for 'R' for the analysis of spatial data. Topics covered include: * statistical formulation and methodological issues * data input and handling * R concepts such as classes and methods ...

✔ Voronoi diagrams&mdash;a survey of a fundamental geometric data structure

[CiTO]
ACM Comput. Surv., Vol. 23, No. 3. (1 September 1991), pp. 345-405, doi:10.1145/116873.116880
posted to by mbedward to the group GeoTools on 2009-03-27 00:22:23 along with 11 people

Abstract

An abstract is not available. ...

Visualizing gridded datasets with large number of missing values

[CiTO]
In Visualization 99. Proceedings (1999), doi:10.1109/VISUAL.1999.809916
posted to by mbedward to the group GeoTools on 2009-03-24 07:04:47

Abstract

Much of the research in scientific visualization has focused on complete sets of gridded data. The paper presents our experience dealing with gridded data sets with a large number of missing or invalid data, and some of our experiments in addressing the shortcomings of standard off-the-shelf visualization algorithms. In particular, we discuss the options in modifying known algorithms to adjust to the specifics of sparse datasets, and provide a new technique to smooth out the side-effects of the operations. We apply ...

✔ Self-organized criticality in forest-landscape evolution

[CiTO]
Physics Letters A, Vol. 297, No. 3-4. (13 May 2002), pp. 267-271, doi:10.1016/s0375-9601(02)00052-x
posted to by mbedward to the group GeoTools on 2009-03-24 03:57:17

Abstract

A simple cellular automaton replicates the fractal pattern of a natural forest landscape and predicts its evolution. Spatial distributions and temporal fluctuations in global quantities show power-law spectra, implying scale-invariance, characteristic of self-organized criticality. The evolution toward the SOC state and the robustness of that state to perturbations are described. ...

✔ CartoDraw: a fast algorithm for generating contiguous cartograms

[CiTO]
Visualization and Computer Graphics, IEEE Transactions on, Vol. 10, No. 1. (2004), pp. 95-110
posted to by ianturton to the group GeoTools on 2009-03-17 13:29:13

Abstract

Cartograms are a well-known technique for showing geography-related statistical information, such as population demographics and epidemiological data. The basic idea is to distort a map by resizing its regions according to a statistical parameter, but in a way that keeps the map recognizable. We formally define a family of cartogram drawing problems. We show that even simple variants are unsolvable in the general case. Because the feasible variants are NP-complete, heuristics are needed to solve the problem. Previously proposed solutions suffer ...

✔ Adaptations for finding irregularly shaped disease clusters

[CiTO]
International Journal of Health Geographics, Vol. 6 (05 July 2007), 28, doi:10.1186/1476-072x-6-28
posted to by ianturton to the group GeoTools on 2009-03-17 13:25:29

✔ A flexibly shaped space-time scan statistic for disease outbreak detection and monitoring

[CiTO]
International Journal of Health Geographics, Vol. 7 (11 April 2008), 14, doi:10.1186/1476-072x-7-14
posted to by ianturton to the group GeoTools on 2009-03-17 13:23:48 along with 1 person

✔ Best analogs for replacing missing image data

[CiTO]
Computers & Graphics, Vol. 31, No. 4. (August 2007), pp. 617-624, doi:10.1016/j.cag.2007.04.002
posted to by mbedward to the group GeoTools on 2009-03-17 06:59:00

Abstract

Identifying the historical data that is the best analog with a pattern from which a forecast is sought allows time series data to be extrapolated. That technique of best analogs is most effective when the data contains underlying deterministic chaos. Here we apply similar techniques, modified to use two space dimensions instead of one time dimension, to fill-in and extrapolate missing image data. The technique is successful at replacing significant amounts of missing data with reasonable data derived from the image ...

An Improved Algorithm for Calculating the Perimeter and Area of Raster Polygons

[CiTO]
GeoComputation 99 Proceedings (1999)
posted to by mbedward to the group GeoTools on 2009-03-17 03:39:02

Abstract

Geographic Information Processing and Digital Cartography, by their very nature, employ digital techniques and sophisticated algorithms for analyzing and displaying digital geographic data. One assumes that the software one uses contains methodologies and algorithms to solve the particular geographic or spatial problem at hand, accurately and precisely. We implicitly have confidence in the implementation of these algorithms, and generally assume that the results produced by these GIS are as accurate as the developers of the software intended them to be. We ...

✔ A simulated annealing strategy for the detection of arbitrarily shaped spatial clusters

[CiTO]
Computational Statistics & Data Analysis, Vol. 45, No. 2. (01 March 2004), pp. 269-286, doi:10.1016/s0167-9473(02)00302-x
posted to by mbedward to the group GeoTools on 2009-03-17 03:28:44 along with 1 person

Abstract

We propose a new graph-based strategy for the detection of spatial clusters of arbitrary geometric form in a map of geo-referenced populations and cases. Our test statistic is based on the likelihood ratio test previously formulated by Kulldorff and Nagarwalla for circular clusters. A new technique of adaptive simulated annealing is developed, focused on the problem of finding the local maxima of a certain likelihood function over the space of the connected subgraphs of the graph associated to the regions of ...

✔ A method for approximating missing data in spatial patterns

[CiTO]
Computers & Graphics, Vol. 28, No. 1. (February 2004), pp. 113-117, doi:10.1016/j.cag.2003.10.012
posted to by mbedward to the group GeoTools on 2009-03-17 02:50:05

Abstract

Spatial patterns such as historical landscape records or digital photographs are often plagued by large numbers of missing or otherwise corrupted data points or pixels that cannot be easily reproduced. A method is described in which a simple stochastic cellular automaton is used to produce fictitious fractal data at arbitrarily many spatial points such that the resulting pattern mimics the morphological features of the actual pattern. The method is simple to implement, preserves all the existing data, has no adjustable parameters, ...

Ribbons: A representation for point clouds

[CiTO]
The Visual Computer, Vol. 23, No. 9-11. (September 2007), pp. 945-954
posted to by mbedward to the group GeoTools on 2009-03-17 01:48:16