Licensing options for this format begin with FME Desktop Professional Edition.
The NGrid Vertical Mapper Reader/Writer module provides FME with access to data in the NGrid format.
Overview
NGrid is a binary raster format with header information. For each raster, there is only a single feature returned, since this feature will contain the entire raster. A single feature is stored in a single file, with header information in an associated MapInfo TAB file.
Reader Overview
FME considers a single NGRID file to be a dataset. NGRID files are raster files containing elevation data. Each elevation sample in the file is translated to a three-dimensional (3D) coordinate that is stored in a single FME raster feature.
Note: FME does not directly support MapInfo Grid (.tab, .grd) files; however, the NGrid reader can read these files.
Writer Overview
FME will write each raster feature to a folder. FME overwrites any existing data contained in that folder. If the writer receives more than one feature, all the rasters are output to files identified by their ngrid_raster_filename attributes. Header information for each raster is given to the NGrid writer as attributes on each raster feature.
The NGrid writer distinguishes duplicate output files by appending numbers to the filenames.
File Types
The NGrid writer outputs different file types depending on whether or not the raster contains a palette:
- .grd: rasters that do not contain a palette
- .grc: rasters that contain a palette
FME Raster Features
FME raster features represent raster data and use several concepts that are unlike those used in the handling of vector data. The topics below describe how FME processes raster data.
NGrid supports rasters with either a single Real32 band, or a single UInt8 or UInt16 band which has an RGB24 and/or String palette.