Hillshade image of the elevation of the A Series observation surface relative to the geoid vertical datum

This hillshade image provides the elevation values that define the observation surface for the "A" series grids relative to the geoid. The "A" Series grids were produced from a combination of ground gravity data for Australian onshore locations, gravity data derived from satellite altimetry for offshore locations, and gravity data from the EGM2008 global gravity model for the onshore locations in countries other than Australia.