Bathymetric Attributed Grid (BAG) Reader/Writer

Licensing options for this format begin with FME Professional Edition.

FME can read and write files that are in the Bathymetric Attributed Grid (BAG) format.

Overview

Bathymetric Attributed Grid is a file format developed by the Open Navigation Surface Working Group for storing and exchanging bathymetric data.

A BAG raster contains two bands. The first band contains elevations. The units of the elevation values are meters, and the sign convention is that positive values represent measures above the vertical datum. The second band describes the vertical uncertainty at each point of elevation. The uncertainty grid supports multiple definitions of uncertainty; the metadata contains information on the meaning of the uncertainty grid.

A BAG file also contains metadata describing who, what, when, where, and how the file was created. This is stored as XML conforming to the ISO 19115 specification. See the bag_metadata_string attribute documentation.

Another component of a BAG file is the tracking list. This list details hydrographer modifications. It is a simple list of original elevation and uncertainty values that have been modified to account for over-rides of the basic surface definition (e.g., as originally computed by an algorithmic method). The tracking list and corresponding information in the metadata provide an audit trail of changes made to the data. See the bag_tracking_list list attribute documentation.

Reader Overview

FME considers a single BAG file to be a dataset. Each dataset contains a single FME raster feature.

Writer Overview

FME considers a dataset to be a folder name. The feature type of each dataset is the filename. The BAG writer distinguishes duplicate output files by appending numbers to the filenames. Please see About FME Rasters for details.

FME Raster Features

FME raster features represent raster data and use several concepts that are unlike those used in the handling of vector data. See About FME Rasters.

BAG only supports rasters with exactly two numeric bands.