forked from ExternalVendorCode/Signal-Server
132 lines
5.0 KiB
Markdown
132 lines
5.0 KiB
Markdown
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SPLAT! Utilities
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Utilities for use with SPLAT! software are found under the
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splat-1.3.0/utils directory. They include the following:
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srtm2sdf
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========
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The srtm2sdf utility generates Data Files (SDFs) for use with Signal-Server
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from STS-99 Space Shuttle Topography Mission (SRTM) elevation data files.
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This data is of a much higher quality than that contained in older USGS
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Digital Elevation Models of the same resolution. However, many SRTM
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Version 2 elevation models contain data "spikes", "voids", and "wells"
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that are the consequence of the radar mapping process.
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The srtm2sdf utility has the ability to detect and replace SRTM data
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outliers with equivalent usgs2sdf derived SDF data (see usgs2sdf below).
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If such data is not available, SRTM outliers are handled either through
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adjacent pixel averaging, or by threshold limiting using user-specified
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limits. Of all three methods, the USGS-derived SDF replacement method
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yields the best results.
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The srtm2sdf utility processes SRTM-3 3-arc second resolution data
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or use with Signal-Server operating in standard definition mode.
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SRTM-3 Version 2 Elevation Data files may be downloaded from:
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ftp://e0srp01u.ecs.nasa.gov:21/srtm/version2/
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Files available at this site are ZIP compressed, and must be
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uncompressed (using "unzip", or "gunzip -S .zip") prior to being
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processed by srtm2sdf.
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The srtm2sdf utility accepts command-line options as follows:
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-d: used to specify the directory path to the location of usgs2sdf
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derived SDF files that are to be used to replace outliers found
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in the SRTM data file. The -d option overrides the default path
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specified in your $HOME/.splat_path file.
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-n: used to specify the elevation (in meters) below which SRTM data
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is either replaced with usgs2sdf-derived SDF data, or averaged
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among adjacent elevation data points. The default threshold for
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the replacement limit is sea-level (0 meters). Unless elevations
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below sea-level are known to exist for the region being
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processed by the srtm2sdf utility, the -n option need not be
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specified.
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Some examples of srtm2sdf use:
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srtm2sdf N40W074.hgt
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srtm2sdf -d /cdrom/sdf N40W074.hgt
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srtm2sdf -d /dev/null N40W074.hgt (/dev/null prevents USGS data
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replacement from taking place)
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srtm2sdf -n -5 N40W074.hgt
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In all cases, SDF files are written into the current working directory.
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The srtm2sdf utility may also be used to convert 3-arc second SRTM data
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in Band Interleaved by Line (.BIL) format for use with SPLAT! This data
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is available via the web at: http://seamless.usgs.gov/website/seamless/
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Once the region of the world has been selected at this site, select the
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"Define Download Area By Coordinates" button under "Downloads". Proceed
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to request the download of the region(s) desired in 1 degree by 1 degree
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regions only, and make sure bounding coordinates entered fall exactly on
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whole numbers of latitude and longitude (no decimal fractions of a degree).
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Select the "Add Area" button at the bottom.
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On the next screen, select "Modify Data Request". On the subsequent screen,
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de-select the National Elevation Dataset (NED) format and select "SRTM 3 arc
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sec - Shuttle Radar Topography Mission [Finished]". Change the format from
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ArcGrid to BIL, and from HTML to TXT.
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Select the "Save Changes and Return To Summary" button.
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Select the "Download" button, and save the file once it has been sent to
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your web browser.
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Uncompressing the file will generate a directory containing all files
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contained within the downloaded archive. Move into the directory and
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invoke srtm2sdf as described above with the filename having the .bil
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extension given as its argument. Finally, move or copy the generated
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.sdf file to your SPLAT! working directory.
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srtm2sdf-hd
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===========
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The srtm2sdf-hd utility operates in an identical manner as srtm2sdf,
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but is used to generate HD SDF files from SRTM-1 one-arc second
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resolution data files for use with signalserverHD. SRTM-1 data files
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are available for the United States and its territories and
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possessions, and may be downloaded from:
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ftp://e0srp01u.ecs.nasa.gov:21/srtm/version2/SRTM1/
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usgs2sdf
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========
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The usgs2sdf utility takes as an argument the name of an uncompressed
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and record delimited Digital Elevation Model Data (DEM) downloaded from
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the US Geological Survey, and generates a SPLAT Data File (SDF) compatible
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with signalserver. usgs2sdf may be invoked manually, or via the
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postdownload.sh script.
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postdownload.sh
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===============
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postdownload.sh is a front-end to the usgs2sdf utility. postdownload.sh
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takes as an argument the name of the gzipped Digital Elevation Model
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(DEM) downloaded from the US Geological Survey (ie: wilmington-w.gz).
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postdownload.sh uncompresses the DEM file, adds necessary record delimiters,
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and invokes usgs2sdf to produce a SPLAT! Data File (SDF).
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USGS Digital Elevation Models may be downloaded from:
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http://edcftp.cr.usgs.gov/pub/data/DEM/250/
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Invoke postdownload with the name of each DEM file downloaded to
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produce a database of SPLAT Data Files.
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---
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John A. Magliacane, KD2BD
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August 2008
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