DTED (Digital Terrain Elevation Data) Feature Representation

In addition to the generic FME feature attributes that FME Workbench adds to all features (see About Feature Type Attributes), this format also adds format-specific attributes (Format Attributes).

Features read from DTED are either 3D points with a feature type of Elevation, or 3D rasters with a feature type of Elevation_raster. Both types have a coordinate system of LL84 (WGS 84 Geographic coordinates).

The DTED writer will write any features with an FME coordinate system that specifies a Latitude Longitude projection and a WGS 84 Geographic datum. These include LL84, LL-WGS84, and WPLL84.

DTED raster features specify a matrix of x, y, and z coordinates.

Attribute Name	Contents
dted_type	This will be set to dted_point or dted_raster depending on the value(s) of AS_DEMRASTER.
dted_raster_filename	This is a string that specifies a destination filename without the extension. It is used in other raster format writers as the basename of the destination file, when writing multiple files. If only one file is written, the destination dataset is used. The DTED writer does not use this attribute because it is a folder writer.
dted_fill_distance	This is a non-negative integer that is used to fill unassigned pixels in output DTED files before flushing them to disk. The value is used to control how far values will be propagated by the fill algorithm. The distance is measured in pixels in the output file. The default value at the feature type level is 1. The maximum value is 16. A value of 0 may be used to disable use of the fill algorithm entirely. Larger values will slow processing substantially due to the nature of the fill algorithm. Pixels assigned values by the fill algorithm are assigned values based on the weighted average of the pixels within the bounding box defined by the fill distance centered on the empty pixel. The weighting is based on inverse square of the distance from the center. Pixels that are not assigned values by points sent to the writer or by the fill algorithm are assigned a “no data” value of -32767 as is defined in the DTED standard.

Attribute Name

Contents

dted_type

This will be set to dted_point or dted_raster depending on the value(s) of AS_DEMRASTER.

dted_raster_filename

This is a string that specifies a destination filename without the extension. It is used in other raster format writers as the basename of the destination file, when writing multiple files. If only one file is written, the destination dataset is used. The DTED writer does not use this attribute because it is a folder writer.

dted_fill_distance

This is a non-negative integer that is used to fill unassigned pixels in output DTED files before flushing them to disk. The value is used to control how far values will be propagated by the fill algorithm. The distance is measured in pixels in the output file.

The default value at the feature type level is 1. The maximum value is 16. A value of 0 may be used to disable use of the fill algorithm entirely. Larger values will slow processing substantially due to the nature of the fill algorithm. Pixels assigned values by the fill algorithm are assigned values based on the weighted average of the pixels within the bounding box defined by the fill distance centered on the empty pixel. The weighting is based on inverse square of the distance from the center.

Pixels that are not assigned values by points sent to the writer or by the fill algorithm are assigned a “no data” value of
-32767 as is defined in the DTED standard.