With the increasing demand for geographic information and position information, the geographic information system (GIS) has come to be widely used in city planning, utilities management, natural resource environments, land surveying, etc. While most GIS maps use vector data to represent geographic information more easily and in greater detail, a GIS vector map can be easily copied, edited, and illegally distributed, like most digital data. This paper presents an invisible, blind, secure, and robust watermarking method that provides copyright protection of GIS vector digital maps by means of arc length distribution. In our method, we calculate the arc lengths of all the polylines/polygons in a map and cluster these arc lengths into a number of groups. We then embed a watermark bit by changing the arc length distribution of a suitable group. For greater security and robustness, we use a pseudo-random number sequence for processing the watermark and embed the watermark multiple times in all maps. Experimental results verify that our method has good invisibility, security, and robustness against various geometric attacks and that the original map is not needed in the watermark extraction process.

With the rapid expansion of vector data model application to digital content such as drawings and digital maps, the security and retrieval for vector data models have become an issue. In this paper, we present a vector data-hashing algorithm for the authentication, copy protection, and indexing of vector data models that are composed of a number of layers in CAD family formats. The proposed hashing algorithm groups polylines in a vector data model and generates group coefficients by the curvatures of the first and second type of polylines. Subsequently, we calculate the feature coefficients by projecting the group coefficients onto a random pattern, and finally generate the binary hash from binarization of the feature coefficients. Based on experimental results using a number of drawings and digital maps, we verified the robustness of the proposed hashing algorithm against various attacks and the uniqueness and security of the random key.

In recent years, digital maps have been used in a variety of scenarios, including car navigation systems and map information services over the Internet. These digital maps are formed by multiple layers of maps of different scales; the map data most suitable for the specific situation are used. Currently, the production of map data of different scales is done by hand due to constraints related to processing time and accuracy. We conducted research concerning technologies for automatic generation of simplified map data from detailed map data. In the present paper, the authors propose the following: (1) a method to transform data related to streets, rivers, etc. containing widths into line data, (2) a method to eliminate the component points of the data, and (3) a method to eliminate data that lie below a certain threshold. In addition, in order to evaluate the proposed method, a user survey was conducted; in this survey we compared maps generated using the proposed method with the commercially available maps. From the viewpoint of the amount of data reduction and processing time, and on the basis of the results of the survey, we confirmed the effectiveness of the automatic generation of simplified maps using the proposed methods.

This study presents a method that can be used to manage individual pieces of information in large scale distributed geographic information systems (GIS). In a distributed GIS, ordinary users usually cannot alter any of the contents on the server. The method in this study can be used to alter the content or add individual datums onto these types of non-write-permitted data sets. The authors have called it a 'Geographic Differential Script File' (GDSF). A client creates a GDSF, which contains private information that is to be added onto the served data. The client keeps this file on a local disk. When the user employs the data, he applies the differential script sequence onto the downloaded data in order to retrieve the information. GDSF is a collection of graphic operation commands which insert and delete objects as well as modify operations. GDSF also contains modifications of the attribute information of geographic entities. This method can also be used to revise information that is published on ROM media, e. g. CD-ROM or DVD-ROM, as well as in a distributed environment. In this paper, the method and results of applying it are presented.