This document provides a justification to the OGC Technical Committee (TC) for consideration of Bathymetric Attributed Grid (BAG) as a Community Standard. This justification, along with the submitted candidate Community Standard, will form the basis for TC review and vote to approve the start of a Work Item as the first step in the Community Standard process for this standard.

The submitters agree to abide by the TC Policies and Procedures and OGC Intellectual Property Rights Policy (http://www.opengeospatial.org/ogc/policies) during the processing of this submission.

Once approved, the Community standard Work Item defined by this document is valid for six (6) months.

The Bathymetric Attributed Grid (BAG) is an open specification for representing bathymetric data as regular grids of seafloor depths with the corresponding vertical uncertainty and associated metadata. These grids are a realization of the Navigation Surface concept defined here, here, and here. See Figure 1 for an example of BAG containing depth, uncertainty, and associated metadata in the form of a raster attribute table (RAT).

The Navigation Surface concept requires that in addition to estimation of depth, an estimate of the uncertainty associated with the depth must be computed and preserved. To make the system suitable for supporting safety of navigation applications, there must be a means to over-ride any automatically constructed depth estimates with "Hydrographer Privilege", (essentially, a means to specify directly the depth determined by a human observer as being the most significant in the area, irrespective of any statistical evidence to the contrary). There is also the requirement to provide data on the data (i.e., metadata, which describe all aspects of the data’s life, from methods of capture to processing methods, and from geospatial extents to a responsible party). The metadata model used by BAG is ISO (International Organization for Standardization) ISO/TS 19115:2003/Cor 1:2006 with ISO/TS 19139 XML encoding.

These and other properties of the BAG data format are described in the BAG Format Specification Document. In addition to this abstract specification of BAG, there is a reference implementation of BAG as a C++ API with Python bindings. A subset of the BAG specification has also been implemented as a GDAL (Geospatial Data Abstraction Library) raster driver, among other implementations.

The BAG specification has been in use for conveying and archiving bathymetry, uncertainty, and metadata by a number of Hydrographic Offices for close to 20 years, including by U.S. National Oceanic and Atmospheric Administration (NOAA) Office of Coast Survey, the US Naval Oceanographic Office, the UK Hydrogaphic Office, and many others. The format is also used by academic partners around the world. The BAG format was developed and is maintained by the Open Navigation Surface Working Group, a collaboration between the core group of NOAA, the US Navy, UNH JHC/CCOM, QPS, Teledyne CARIS™, and Leidos, as well as other interested parties. BAG files are accessible in several Geographic Information Systems (GISs), such as Esri ArcGIS, Teledyne CARIS Base Editor, and QGIS (Quantum GIS) and in visualization applications such as QPS Fledermaus. Hydrographic processing applications such as QPS Qimera, CARIS HIPS, and Leidos Saber also use BAG as a format for processed data. Software libraries such as the BAG library and GDAL facilitate access to BAG data. BAG use in these various applications is rarely feature-complete with each focusing on specific features needed in each context. Further, varying expectations on the use cases for the BAG format make interoperability a struggle. To resolve these issues we submit the adoption of BAG as an OGC Community Standard to improve FAIR principles for bathymetry stored in the BAG format through increased accessibility, interoperability, and reuse.

The BAG data model is an application of the Hierarchical Data Format version 5 (HDF5) data model. Further, all BAG data are encoded as HDF5 files.

Further standardization and adoption of the BAG format can help to make bathymetric data more Findable, Accessible, Interoperable, and Reusable (FAIR). Making geospatial data FAIR is a key goal of OGC as well as the BAG sponsor organizations (such as NOAA’s Office of Coast Survey).

The BAG Community Standard will help to further OGC’s efforts in the Marine Domain, specifically by serving as a key data format for bathymetric data for use in the development of Federated Marine Spatial Data Infrastructure (SDI).

The following implementations use the proposed Community standard. Commercial software packages that support reading or writing BAG data (e.g., CARIS Base Editor, CARIS HIPS, Esri ArcGIS, Leidos Saber, QGIS, QPS Qimera) tend to use either implementation to provide support for BAG (rather than develop their own implementation).

Is the proposed Community Standard currently publicly available?

URL: https://bag.readthedocs.io/en/master/fsd/index.html

Will the contributor retain intellectual property rights?

BAG Community Standard will be released under the same BSD 3-Clause License as the BAG reference implementation.