Digital watermark: technique, application and improvement as a copyright-protecting method for RS and cartographic data

Digital watermark techniques are now eventually becoming one of the most reliable methods to prove the copyright of both observed and processed digital marine data, especially when the data have to be distributed through Internet. The article introduced the research work, which we finished on the application and improvement of digital watermark techniques for the copyright-proving of remotely sensed topographic data and marine cartographic data, with the emphasis on mathematical models and application methods. Discussions on different models and methods were made based on the results of our experiments. The article also put forward several feasible application methods for the purpose of copyright protection, such as the method of embedded image or texts, the fragile watermarks and captioning, etc. The watermarks for vector data, which is particularly valuable for digital charts, are also discussed.