12.0 Coordinate Reference Systems

All data and corresponding products submitted to the Office of Coast Survey must include metadata to describe the critical elements of the associated coordinate reference system (CRS) definitions. The WKT representation of the relevant geodetic, vertical, or compound CRS must be used, in accordance with the provisions of International Organization for Standardization (ISO) 19111:2007 and ISO 19111-2:2009, developed in collaboration with the Open Geospatial Consortium (OGC). The CRS WKT 2015 or later specification (“WKT2”) is preferred. The WKT2 bound CRS syntax may be used for the CRS metadata as required, to facilitate the interrelationship of a new CRS realization associated with data (bound CRS’ source CRS) to that of an established geodetic CRS (bound CRS’ target CRS) via a given coordinate transformation. For example, metadata for NOAA VDatum geoidal-tidal based CRS realizations can be described in WKT via the bound CRS syntax. An example of a bound CRS that meets the requirements of this specification is provided by the Open Navigation Surface Working Group (ONSWG) as part of the BAG 2.0 metadata specification. ISO Geodetic Registry (ISOGR) or EPSG codes included within the WKT are helpful, if available. Standalone EPSG codes as a replacement for WKT are not acceptable. 

 

Table 12.0.0 CRS Metadata

  1. Element
  1. Mandatory/Conditional/Optional
  1. See Note
  1. Coordinate Reference System Name
  1. M
  1.  
  1. Length Units
  1. M
  1.  
  1. Axis Direction
  1. M
  1.  
  1. Epoch
  1. C
  1. 1
  1. Geoid
  1. C
  1. 2
  1. Ellipsoid/Spheroid
  1. C
  1. 3
  1. Projection
  1. C
  1. 4

Notes

1 If a dynamic coordinate reference system is used.

2 If a geoid-based vertical coordinate reference system is used.

3 If a geodetic reference frame is used.

4 If a projected coordinate reference system is used.

 

To identify the accuracy of the reference frame precisely through metadata, CRS having a datum ensemble should not be used for products delivered to the Office of Coast Survey; instead, select the appropriate reference frame member from the ensemble to encode in the WKT metadata.

 

For NOAA ISD surveys, WKT CRS metadata will be provided to the Field Unit with the Project Instructions and it must serve as the CRS requirements for the project.