Geodetic World Height System Unification

Abstract

Elevations are one of the positional attributes embedded in all geospatial data. They are essential for a wide range of engineering and scientific activities. Some of the activities requiring precise elevations are activities of high societal impacts, such as sea level rise, storm surges and coastal inundation, floods and evacuation route planning, and crustal motion, subsidence, and other surface deformations due to seismic, mining, or other events. In order to successfully monitor and manage such events regionally (e.g., floods) or globally (e.g., sea level rise), the elevation information needs to not only be accurate but to also refer to the same zero-height reference surface (vertical datum). Accurate elevations can be obtained using spirit leveling, or by combining Global Navigation Satellite Systems (GNSS) positioning methods with a model of the geoid (the equipotential surface of the Earth's gravity field approximating the idealized mean sea surface). So although the high accuracy requirements can in general be met, the need for a common reference surface often cannot. This is because there are currently over 100 different vertical datums around the world. Their unification is therefore a scientific problem of high practical significance.