This guidance note discusses issues associated with vertical Coordinate Reference Systems (CRSs), in particular those related to coordinate operations (coordinate conversions and coordinate transformations) and metadata.
Horizontal and vertical data are equally important in oil and gas exploration and development processes, and incomplete attention to either can impact the integrity, resolution and accuracy of the resultant datasets.
Vertical data (height and depth) are inherently important data used in oil and gas exploration and production activities. The vertical component of seismic profiles, 3D volumes, well, pipeline and other infrastructure data are fundamental to oil and gas activities, and form the basis for the creation of subsequent datasets used for engineering in the subsurface environment and also in well planning, modelling, and integrity and flow management.
Typically, vertical data is not worked to the same level of detail as horizontal data, and the perceived accuracy of the vertical data is often higher than reality. There is generally insufficient attention to reference surfaces and inconsistent use of terminology which can result in erroneous offsets being introduced to datasets. Axis directions (heights and depths) are frequently interchanged without an appropriate audit trail. These errors are often the result of transferring data between applications, either through software exchanges or common data exchange formats without the transfer of the associated metadata, including an explicit definition of the vertical geodetic datum and CRS.
This guidance note describes the basic concepts of vertical CRSs and reference surfaces used with vertical data. The importance of recording data operations and associated metadata to ensure the unambiguous referencing of vertical data and preservation of data accuracy is stressed.
It addresses two key groups of stakeholders: those that use and/or manage vertical data; and those involved in software development. It is aimed at geoscientists, data managers and software developers. Guidance is provided to understand, use and implement