+The srtm2sdf utility accepts command-line options as follows:
+
+-d: used to specify the directory path to the location of existing
+ SDF files (presumably created at an earlier date through the
+ usgs2sdf or postdownload utility) that are to be used to replace
+ outliers found in the SRTM data file. The -d option overrides
+ the default path specified in your $HOME/.splat_path file.
+
+-n: used to specify the elevation (in meters) below which SRTM data
+ is replaced. Below this limit, SRTM elevation data is either
+ replaced using existing SDF equivalent files, or averaged among
+ adjacent elevation data points. The default threshold for the
+ replacement limit is sea-level (0 meters). Unless elevations
+ below sea-level are known to exist for the region being
+ processed by the srtm2sdf utility, the -n option need not be
+ specified.
+
+Some examples of srtm2sdf use:
+
+ srtm2sdf N40W074.hgt
+
+ srtm2sdf -d /cdrom/sdf N40W074.hgt
+
+ srtm2sdf -d /dev/null N40W074.hgt (/dev/null prevents USGS data
+ replacement from taking place)
+
+ srtm2sdf -n -5 N40W074.hgt
+
+In all cases, SDF files are written into the current working directory.