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The Nautical Cartographic Constraints and an Automated Generalization Model
Nada Tamer1, Kastrisios Christos1, Calder Brian1, Ence Christie2
Greene Craig3, Bethell Amber3, Hosuru Madhu3
1Center for Coastal and Ocean Mapping/UNH-NOAA Joint Hydrographic Center, University of New Hampshire, Durham, NH, USA
2 NOAA, Office of Coast Survey, Marine Chart Division, Silver Spring, MD, USA
3ESRI, Marine & Topographic Production Division, Redlands, CA, USA
tnada@ccom.unh.edu
Current methods for nautical charts generalization are strongly human interactive and time-consuming.
Significant amounts of effort are needed for generalizing, compiling, updating, maintaining, and consistency
checking those products. The ideal situation would be a fully automated solution for generating products on
demand, at the right scale, at the point of use, and directly from the seamless database, that respect all
application specific constraints (i.e., Safety, Legibility, Topology, and Morphology). Such a solution would
solve many related problems, minimize the time and effort needed for ENC production and support rapid
update. However, regardless of the advancements in technology and the various research efforts,
generalization tasks for nautical chart compilation are still performed mostly manually or semi-manually,
where a likelihood of human error must be admitted. Furthermore, practice has shown that there is often a
trade off among the various generalization constraints as fixing one violation may result in the violation of
another constraint.
Towards this optimum goal, we are conducting a project that aims to investigate the previous efforts for
automated map production, review the available relevant nautical cartographic standards and specifications,
and extract and categorize the nautical chart generalization guidelines thereinto. These are subsequently
translated into rules and defined in a template as conditions to be respected during the generalization process.
According to a hierarchy level, a cost will be related to any violation according to its importance to the safety
of navigation. Since fully satisfying all constraints seems infeasible, the optimal generalized chart should be
the one with the lowest cost. For the implementation, a multi-agent generalization model is under
development in the ESRI nautical environment that will utilize the template and the source data within the
areas of interest to perform the generalization for the target scale (Figure).
Figure: The concept of the nautical generalization model