+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.
+
+The srtm2sdf utility may also be used to convert 3-arc second SRTM data
+in Band Interleaved by Line (.BIL) format for use with SPLAT! This data
+is available via the web at: http://seamless.usgs.gov/website/seamless/
+
+Once the region of the world has been selected at this site, select the
+"Define Download Area By Coordinates" button under "Downloads". Proceed
+to request the download of the region(s) desired in 1 degree by 1 degree
+regions only, and make sure bounding coordinates entered fall exactly on
+whole numbers of latitude and longitude (no decimal fractions of a degree).
+
+Select the "Add Area" button at the bottom.
+
+On the next screen, select "Modify Data Request". On the subsequent screen,
+de-select the National Elevation Dataset (NED) format and select "SRTM 3 arc
+sec - Shuttle Radar Topography Mission [Finished]". Change the format from
+ArcGrid to BIL, and from HTML to TXT.
+
+Select the "Save Changes and Return To Summary" button.
+
+Select the "Download" button, and save the file once it has been sent to
+your web browser.
+
+Uncompressing the file will generate a directory containing all files
+contained within the downloaded archive. Move into the directory and
+invoke srtm2sdf as described above with the filename having the .bil
+extension given as its argument. Finally, move or copy the generated
+.sdf file to your SPLAT! working directory.