Cartesian offset Offset expressed using cartesian coordinates where X is distance along axis aligned with true north, Y is distace aligned with true east, and Z is distance aligned straight up. Depths are expressed a negative numbers. The origin of the coordinate system is typically defined in the site description. 3D ODM2 Spatial Offset Type Controlled Vocabulary ODM2 Working Group A vocabulary for describing the type of SpatialOffset that exists between two SamplingFeatures.