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utils/sdf/README.md

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+			================
+			SPLAT! Utilities
+			================
+
+Utilities for use with SPLAT! software are found under the
+splat-1.3.0/utils directory.  They include the following:
+
+
+srtm2sdf
+========
+The srtm2sdf utility generates Data Files (SDFs) for use with Signal-Server
+from STS-99 Space Shuttle Topography Mission (SRTM) elevation data files.  
+This data is of a much higher quality than that contained in older USGS
+Digital Elevation Models of the same resolution.  However, many SRTM
+Version 2 elevation models contain data "spikes", "voids", and "wells"
+that are the consequence of the radar mapping process.
+
+The srtm2sdf utility has the ability to detect and replace SRTM data
+outliers with equivalent usgs2sdf derived SDF data (see usgs2sdf below).
+If such data is not available, SRTM outliers are handled either through
+adjacent pixel averaging, or by threshold limiting using user-specified
+limits.  Of all three methods, the USGS-derived SDF replacement method
+yields the best results.
+
+The srtm2sdf utility processes SRTM-3 3-arc second resolution data
+or use with Signal-Server operating in standard definition mode.
+
+SRTM-3 Version 2 Elevation Data files may be downloaded from:
+
+    ftp://e0srp01u.ecs.nasa.gov:21/srtm/version2/
+
+Files available at this site are ZIP compressed, and must be
+uncompressed (using "unzip", or "gunzip -S .zip") prior to being
+processed by srtm2sdf.
+
+The srtm2sdf utility accepts command-line options as follows:
+
+-d:  used to specify the directory path to the location of usgs2sdf
+     derived SDF files 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 either replaced with usgs2sdf-derived SDF data, 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.
+
+
+srtm2sdf-hd
+===========
+The srtm2sdf-hd utility operates in an identical manner as srtm2sdf,
+but is used to generate HD SDF files from SRTM-1 one-arc second
+resolution data files for use with signalserverHD.  SRTM-1 data files
+are available for the United States and its territories and
+possessions, and may be downloaded from:
+
+    ftp://e0srp01u.ecs.nasa.gov:21/srtm/version2/SRTM1/
+
+
+usgs2sdf
+========
+The usgs2sdf utility takes as an argument the name of an uncompressed
+and record delimited Digital Elevation Model Data (DEM) downloaded from
+the US Geological Survey, and generates a SPLAT Data File (SDF) compatible
+with  signalserver.  usgs2sdf may be invoked manually, or via the
+postdownload.sh script.
+
+
+postdownload.sh
+===============
+postdownload.sh is a front-end to the usgs2sdf utility.  postdownload.sh
+takes as an argument the name of the gzipped Digital Elevation Model
+(DEM) downloaded from the US Geological Survey (ie: wilmington-w.gz).
+postdownload.sh uncompresses the DEM file, adds necessary record delimiters,
+and invokes usgs2sdf to produce a SPLAT! Data File (SDF).
+
+USGS Digital Elevation Models may be downloaded from:
+
+    http://edcftp.cr.usgs.gov/pub/data/DEM/250/
+
+Invoke postdownload with the name of each DEM file downloaded to
+produce a database of SPLAT Data Files.
+
+---
+John A. Magliacane, KD2BD
+August 2008
+