ATIS 0500045

This Technical Report will be used as a vehicle for communicating elevation or height acquisition concepts in liaisons with other relevant Standards Development Organizations (SDOs). The Z-axis information associated with location estimates can be reported using either ellipsoidal or orthometric height, among other representations. This report describes the terms used to represent height and then elaborates the ellipsoidal versus orthometric representations of height. It also provides an overview of the uncertainty shapes used in representing Z-axis information and adds clarifying visualizations. It offers recommendations for the end-to-end delivery of Z-axis information and includes suggested mappings for both 2D and 3D uncertainty shapes, exploring some limitations and risks associated with the mapping process. This report investigates each shape but does not presume that any single shape will be used universally. The various tables within the document specify uncertainty shape mapping recommendations and highlight impacts to downstream entities.