Design and development for updating national 1:50,000 topographic databases in China

1.1 Objective Map databases are irreplaceable national treasure of immense importance. Their currency referring to its consistency with respect to the real world plays a critical role in its value and applications. The continuous updating of map databases at 1:50,000 scales is a massive and difficult task for larger countries of the size of more than several million’s kilometer squares. This paper presents the research and technological development to support the national map updating at 1:50,000 scales in China, including the development of updating models and methods, production tools and systems for large-scale and rapid updating, as well as the design and implementation of the continuous updating workflow. 1.2 Methodology The updating of map databases is different than its original creation, and a number of new problems should be solved, such as change detection using latest multi-source data, incremental object revision and relation amendment. The methodology of this paper consists of the following three parts: 1) Examine the four key aspects of map database updating and develop basic updating models/methods, such as currentness-oriented integration of multi-resource data, completeness-based incremental change detection in the context of existing datasets, consistency-aware processing of updated data sets, and user-friendly propagation and services of updates. 2) Design and develop specific software tools and packages to support the large-scale updating production with high resolution imagery and large-scale data generalization, such as map generalization, GIS-supported change interpretation from imagery, DEM interpolation, image matching-based orthophoto generation, data control at different levels. 3) Design a national 1:50,000 databases updating strategy and its production workflow, including a full coverage updating pattern characterized by all element topographic data modeling, change detection in all related areas, and whole process data quality controlling, a series of technical production specifications, and a network of updating production units in different geographic places in the country. 1.3 Results A group of updating models and technical methods were proposed after a systematic investigation of the key problems arising from the continuous updating of national 1:50,000 map databases. A set of specific software tools and packages was further developed to support large area updating. With these innovative methodologies and tools, a total of 19,150 map sheets at 1:50,000 scales had been updated and such a massive task was completed in an acceptable time frame, i.e., from 2060-2010. The data currency of national 1:50,000 map databases has been raised from 20-30 years to 5 years! 1.4 Conclusion A modern state requires accurate up to date maps and keeping them up to date on a regular basis is a massive task for a country the size of China. National Geomatics Center of China (NGCC) has solved this problem by using the latest data sources and developing new techniques. The methodologies developed in this paper are suited to regular updating in other rapidly developing nations and establish a model which can be followed in similar circumstances throughout the world.