The directives that are processed by the USGS DEM reader are listed below. The suffixes shown are prefixed by the current <ReaderKeyword>_ in a mapping file. By default, the <ReaderKeyword> for the USGS DEM reader is USGS_DEM.
DATASET
Required/Optional: Required
The value for this directive is the name of a single USGS DEM file. The normal extension for USGS DEM files is .dem.
An example of the DATASET directive in use is:
USGS_DEM_DATASET C:\DATA\DEM\portland.dem
Workbench Parameter: Source U.S. Geological Survey DEM File(s)
SAMPLE
Required/Optional: Optional
USGS DEM files can produce large raster features, or a lot of point features. Sometimes, it is desirable to extract only a subsample of the features, while maintaining a regular raster pattern of points. The SAMPLE directive is used to specify a decimation factor that is applied in the vertical direction.
A SAMPLE value of 3, for instance, results in only one in three points in the vertical direction being returned from the reader. As a result, only one-third of points are created into features.
An example of how the directive SAMPLE might be used is given below:
USGS_DEM_SAMPLE 3
In the above example, the value given to the SAMPLE directive was 3.
Workbench Parameter: Decimation Factor
AS_DEMRASTER
Required/Optional: Optional
USGS DEM files can be interpreted by FME as a group of associated point features or as a single raster feature. The AS_DEMRASTER directive is used to specify which way FME will handle the raster. Raster files can be translated much more efficiently as raster features than as many point features.
An AS_DEMRASTER value of no, for instance, results in the handling of elevation values in a raster file as individual point features. A value of yes, conversely, results in the handling of each raster file as a single raster feature.
USGSDEM_AS_DEMRASTER yes
GROUP_BY_DATASET
When the value is set to No, the only feature type this reader will use is the reader type name.
When the value is set to Yes, the feature type of each dataset is the filename (without the path or the extension) of the dataset.
Required/Optional
Required
Values
YES | NO (default)
Mapping File Syntax
GROUP_BY_DATASET “Yes”
Workbench Parameter
Feature Type Name(s)
EXPOSED_ATTRS
This directive allows the selection of format attributes to be explicitly added to the reader feature type.
This is similar to exposing format attributes on a reader feature type once it has been generated; however, it is even more powerful because it enables schema-driven applications other than Workbench to access and leverage these attributes as if they were explicitly on the schema as user attributes.
The result of picking a list of attributes is a comma-separated list of attribute names and types that will be added to the schema features. Currently all reader feature types will receive the same set of additional schema attributes for a given instance of the reader.
Required/Optional
Optional
Mapping File Syntax
Not applicable.
While it is possible for FME Objects applications to invoke this directive, the required format is not documented.
This directive is intended for use in our GUI applications (for example, Workbench) only.
Workbench Parameter
Additional Attributes to Expose