Cartographic Generalization in Digital Environment

Throughout the world numerous efforts to automate generalization are in progress. The results are yet to be satisfactory. Ample reasoning can be given to justify the lack of success, the most important being that generalization is an ambiguous process, highly subjective which lacks definitive rules, guidelines or systematization. This paper deals with the problem of generalization of vector data bases through the analysis of recent developments and research in the field. These developments tend to establish a promising framework which, with subsequent refinements and the utilization of state-of-the-art computer technology, may lead to successful results. What is needed is what lacks: Definitive rules in structuring the digital image of the world and development of expert systems which will intelligently manipulate this image

An Integrated Environment for Monitoring and Documenting Quality in Map Composition Utilizing Cadastral Data

Topographic maps show both physical and artificial entities of the surface of the Earth which represent distinct features forming the building blocks in map composition. Their portrayal on the map is subject to constraints dependent on the method of data collection, the map scale, the data processing procedures and the requirements of map users. In addition to constraints, geospatial data contain uncertainties and errors that are either inherent in the data or a result of the map composition process. The type and significance of these errors determine the quality of maps. This paper elaborates on the development of an integrated environment for monitoring and documenting quality in the map composition process. In this environment, quality plays a vital role in all phases of map production whereby it is continuously assessed and documented. The methodology described involves the design and implementation of a “quality model” based on international Standards. An integrated software application for the utilization of cadastral information to produce and update topographic maps at a scale of 1:25,000 was also developed. The aim is to implement the proposed methodology in a real production environment and to use it as a proof of concept

"A Methodology for the Assessment of Generalization Quality"

Generalization quality assessment is a major issue in contemporary cartography. Besides the evaluation of generalization results, it supports the research for the automation of generalization. In this paper, two methods, based on structure and shape recognition, are elaborated: the parametric description of line shape and the partitioning of linear features into homogeneous segments. A number of quantitative measures for the assessment of line shape change due to generalization are identified. These measures provide an “a posteriori” evaluation of generalization alternatives, which result from the application of different generalization operators (i.e. simplification, smoothing), algorithms and tolerance values, onto a number of linear features of varying degree of complexity. In combination with existing quantitative measures for the horizontal position error, these measures constitute an efficient approach for the positional accuracy assessment at the individual object level. Specific tools, like graphs and tables, are proposed for the study of the positional accuracy aspect of any generalization schema. The application of this methodology will lead to the formulation of criteria, which can be used for the selection of the most suitable generalization solution and subsequently to knowledge acquisition and the development of a knowlwdge base to support automated map generalization. 1. Cartographic generalization and qualit

Generalization of Linear and Area Features Incorporating a Shape Measure

This article elaborates on the quality issue in cartographic generalization of linear and area features focusing on the assessment of shape preservation. Assessing shape similarity in generalization is still a topic where further research is required. In the study presented here, shape description and matching techniques are investigated and analyzed, a procedure for choosing generalization parameters suitable for line and area features depiction is described and a quality model is developed for the assessment and verification of the generalization results. Based on the procedure developed, cartographers will be confident that the generalization of linear and area features is appropriate for a specific scale of portrayal fulfilling on the same time a basic requirement in generalization, that of shape preservation. The results of the procedure developed are based on the processing and successful generalization of a large number of different line and area features that is supported by a software environment developed in Python programming language

An Integrated Environment for Monitoring and Documenting Quality in Map Composition Utilizing Cadastral Data

Topographic maps show both physical and artificial entities of the surface of the Earth which represent distinct features forming the building blocks in map composition. Their portrayal on the map is subject to constraints dependent on the method of data collection, the map scale, the data processing procedures and the requirements of map users. In addition to constraints, geospatial data contain uncertainties and errors that are either inherent in the data or a result of the map composition process. The type and significance of these errors determine the quality of maps. This paper elaborates on the development of an integrated environment for monitoring and documenting quality in the map composition process. In this environment, quality plays a vital role in all phases of map production whereby it is continuously assessed and documented. The methodology described involves the design and implementation of a “quality model” based on international Standards. An integrated software application for the utilization of cadastral information to produce and update topographic maps at a scale of 1:25,000 was also developed. The aim is to implement the proposed methodology in a real production environment and to use it as a proof of concept

Constraint-Based Spatial Data Management for Cartographic Representation at Different Scales

This article elaborates on map-quality evaluation and assessment as a result of the generalization of geospatial data through the development of a methodology, which incorporates a quality data model including constraints. These constraints are used to guide the generalization process and they operate as requirements in quality controls applied for the quality evaluation and assessment of the resulting cartographic data. The quality model stores the required map specifications compiled as constraints, and provides quality measures along with new techniques for the evaluation and assessment of cartographic data quality. This secures the map composition process in each and every step and for all features involved, at any map scale. The methodology developed results in the creation of a scale-dependent cartographic database that contains exclusively the features to be portrayed on the map, generalized properly according to the map scale. It will reduce cartographers’ need to review each transformation throughout the map-composition process with considerable savings in time and money and, on the other hand, it will secure the quality of the final map. The formulation of the proposed methodology amalgamates generalization theory with the authors’ research in computer-assisted cartography, taking into account the work conducted on the topic by other researchers. In this study, the quality requirements, the measures and the associated techniques together with the results of the application of the proposed methodology for area and line features are described in detail to allow others to replicate and build on the presented results

Voronoi tessellation on the ellipsoidal earth for vector data

<p>Voronoi tessellation, and its dual the Delaunay triangulation, provide a cohesive framework for the study and interpretation of phenomena of geographical space in two and three dimensions. The planar and spherical solutions introduce errors in the positional accuracy of both Voronoi vertices and Voronoi edges due to errors in distance computations and the path connecting two locations with planar lines or great circle arcs instead of geodesics. For most geospatial applications the introduction of the above errors is insignificant or tolerable. However, for applications where the accuracy is of utmost importance, the ellipsoidal model of the Earth must be used. Characteristically, the introduction of any positional error in the delimitation of maritime zones and boundaries results in increased maritime space for one state at the expense of another. This is a situation that may, among others, have a serious impact on the financial activities and the relations of the states concerned. In the context of previous work on maritime delimitation we show that the Voronoi diagram constitutes the ideal solution for the development of an automated methodology addressing the problem in its entirety. Due to lack of a vector methodology for the generation of Voronoi diagram on the ellipsoid, the aforementioned solution was constrained by the accuracy of existing approaches. In order to fill this gap, in this paper we deal with the inherent attributes of the ellipsoidal model of the Earth, e.g. the fact that geodesics are open lines, and we elaborate on a methodology for the generation of the Voronoi diagram on the ellipsoid for a set of points in vector format. The resulting Voronoi diagram consists of vertices with positional accuracy that is only bounded by the user needs and edges that are comprised of geodesics densified with vertices equidistant to their generators. Finally, we present the implementation of the proposed algorithm in the Python programming language and the results of two case studies, one on the formation of closest service areas and one on maritime boundaries delimitation, with the positional accuracy set to 1 cm.</p

A Constraint-Based Generalization Model Incorporating a Quality Control Mechanism

Automation in map production has created the need for modeling the map composition process. Generalization is the most critical process in map composition, with considerable impact on the quality of features portrayed on the maps. Modeling of the generalization process has been an area of research for several years in the international cartographic community. Constraint-based generalization modeling prevailed, and it is evolving to an agent model or to other optimization models. The generalization model presented in this paper is based on constraint-based modeling. It introduces the standardization of the semantic and cartographic generalization process together with an evaluation mechanism for the assessment of the quality of the resulting cartographic data considering simultaneously the preservation of the shape of the portrayed linear and area features. For cartographers, quality management is a key factor in creating an evidence-based, reliable product. To achieve this objective, cartographers, drawing on international experience, should implement a quality policy and adopt a quality management system (QMS) as an integral part of the map production process, starting with the quality assessment of the input data and finishing with the evaluation of the final product

Generalization of Soundings across Scales: From DTM to Harbour and Approach Nautical Charts

This paper presents an integrated digital methodology for the generalization of soundings. The input for the sounding generalization procedure is a high resolution Digital Terrain Model (DTM) and the output is a sounding data set appropriate for portrayal on harbour and approach Electronic Navigational Charts (ENCs). The sounding generalization procedure follows the &ldquo;ladder approach&rdquo; that is a requisite for the portrayal of soundings on nautical charts, i.e., any sounding portrayed on a smaller scale chart should also be depicted on larger scale charts. A rhomboidal fishnet is used as a supportive reference structure based on the cartographic guidance for soundings to display a rhombus pattern on nautical charts. The rhomboidal fishnet cell size is defined by the depth range and the compilation scale of the charted area. Generalization is based on a number of rules and constraints extracted from International Hydrographic Organization (IHO) standards, hydrographic offices&rsquo; best practices and the cartographic literature. The sounding generalization procedure can be implemented using basic geoprocessing functions available in the most commonly used Geographic Information System (GIS) environments. A case study was performed in the New York Lower Bay area based on a high resolution National Oceanic and Atmospheric Administration (NOAA) DTM. The method successfully produced generalized soundings for a number of Harbour and Approach nautical charts at 10 K, 20 K, 40 K and 80 K scales

Management of Marine Rights, Restrictions and Responsibilities according to International Standards

The interests, responsibilities and opportunities of states to provide infrastructure and resource management are not limited to their land territory but extend to marine areas as well. So far, although the theoretical structure of a Marine Administration System (MAS) is based on the management needs of the various countries, the marine terms have not been clearly defined. In order to define a MAS that meets the spatial marine requirements, the specific characteristics of the marine environment have to be identified and integrated in a management system. To explicitly define MAS, certain issues need to be addressed such as: the types of interests that exist in marine environment, the best way to capture and register those interests, laws defining these interests, and their hierarchical classification, as well as how this classification can be used to produce the principles for the implementation of MSP. In addition, the registration of laws in a MAS that could automatically define the constraints of the emerging Rights, Restrictions and Responsibilities (RRRs) should be addressed, along with property/ tenure object definition. Further questions need to be answered e.g., what is the basic reference unit and how can this be defined, deliminated and demarcated, capturing the 3D presence of marine parcel and is the traditional definition of a cadastral parcel applicable in a marine zone defined by United Nations Convention on Law of the Sea (Hereinafter: UNCLOS) (United Nations, 1982) and how could the fourth dimensional nature of marine RRRs be included. Addressing these questions constitutes the basis upon which a MAS can be built. However, the most crucial question is how the international standards and practices of land administration domain can be used for managing the marine environment. The aim of this paper is to examine the above questions, to probe the ways the legislation can be included into a MAS and to present how RRRs relating to marine space may be defined and organized, in order to develop a MAS based on international standards by means of not only trading in marine interests, but rather facilitating the management of activities related to resources