Simplification methods for line and polygon features in mobile navigation systems for inland waters

Mobile navigation for inland shipping is an example of a GIS system dedicated for recreational users using inland waterways. Developing this system is a primary purpose of the research project “Mobile Navigation for Inland Waters” funded by the National Centre for Research and Development under the program LIDER. System assumptions include the development of a dedicated model of mobile cartographic presentation, taking into account the generalization of data. This article is focused on simplification of line and polygon features, included in the spatial data model MODEF (MObinav Data Exchange Format), which is used in the created system. During the simplification of line features, the Douglas-Peucker algorithm was mainly implemented. During the simplification of polygon features, a simplification method was applied, maintaining the basic shape and size of the objects. A simplification tolerance parameter and a parameter determining the minimum area of the object was also used. In addition, objects within a certain distance were merged. A smoothing tool for the shape and size of buildings and the PEAK method (Polynomial Approximation with Exponential Kernel) were used as well. Furthermore, a selection tool was employed and features with minor importance to the user were deleted during navigation mode. Given the requirements of the future user of the system, a separate model simplification for each of the layers of the system was created; these models are combinations of the methods listed above. The overriding factor that has been taken into account during the research of simplification methods, was the limitation of the sharpness of human eyes. The study of generalization methods was carried out in ArcGIS software.