Gradual Generalization of Nautical Chart Contours with a Cube B-Spline Snake Model

—B-spline snake methods have been used in cartographic generalization in the past decade, particularly in the generalization of navigational charts where this method yields good results with respect to the shoal-bias rules for generalization of chart contours. However, previous studies only show generalization results at particular generalization (or scale) levels, and the user can only see two conditions: before the generalization and after generalization, but nothing in between. This paper presents an improved method of using B-spline snakes for generalization in the context of nautical charts, where the generalization process is done gradually, and the user can see the complete process of the generalization

Topologically safe curved schematization

Traditionally schematized maps make extensive use of curves. However, automated methods for schematization are mostly restricted to straight lines. We present a generic framework for topology-preserving curved schematization that allows a choice of quality measures and curve types. Our fully-automated approach does not need critical points or salient features. We illustrate our framework with Bézier curves and circular arcs

Gradual Generalization of Nautical Chart Contours with a B-Spline Snake Method

B-spline snake methods have been used in cartographic generalization in the past decade, particularly in the generalization of nautical charts where these methods yield good results with respect to the shoal-bias rules for the generalization of chart contours. However, previous studies only show generalization results at particular generalization (or scale) levels, and show only two states of the algorithm: before and after generalization, but nothing in between. This thesis presents an improved method of using B-spline snakes and other auxiliary functions and workflows for generalization in the context of nautical charts which can generalize multiple nautical chart features from large scale to small scale without creating any invalid intermediate features that require special processing to resolve. This process allows users to generate charts at any intermediate scale without cartographic irregularities, and is capable of extension to include more specialized generalization operators

Feature-driven generalisation of isobaths on nautical charts : a multi-agent system approach

A nautical chart provides a schematic view of the seafloor where isobaths (contour lines joining points of same depth) and depth soundings are generalised to highlight undersea features that form navigational hazards and routes. Considering that the process is ultimately driven by features and their significance to navigation, this article proposes a generalisation strategy where isobath generalisation is controlled by undersea features directly. The seafloor is not perceived as a continuous depth field but as a set of discrete features composed by groups of isobaths. In this article, generalisation constraints and operators are defined at feature level and composed of constraints and operators applying to isobaths. In order to automate the process, a multi-agent system is designed where features are autonomous agents evaluating their environment in order to trigger operations. Interactions between agents are described and an example on a bathymetric database excerpt illustrates the feasibility of the approach

Generalisation of submarine features on nautical charts

2012-2013 > Academic research: refereed > Refereed conference paperVersion of RecordPublishe