Towards one domain model and one key register topography

Two domain models for topography have been independently established in the Netherlands: Information Model Geography (for large scale topography) and TOP10NL (for small scale topography). The two domain models IMGeo and TOP10NL model the content and meaning of existing datasets which will be legally established as key registers for the national Spatial Data Infrastructure (SDI). Since both domain models and corresponding datasets represent the same types of object and cover the same geographical extent, the question is if one domain model and one register topography will be feasible to serve the notion of 'collect once, use many times' within the Dutch SDI. This paper contains a thorough comparison of how similar concepts in the two domain models are defined. The conclusion is that two key registers topography need to be kept for the moment. The main reason is the differences in content due to differences in data source, providers, objectives and stake holders. However since many differences seem random and easy to solve, harmonising of concepts is recommended before integrating the models. For the integration the paper proposes a Base Model Topography that models how TOP10NL data can be derived from IMGeo data to serve the goal: collect data once, maintain it at two key registers to use it many times.